This superb article emphasizes the very high importance of a team approach when undertaking CT dose management.
Our experience at UW Medicine Radiology mirrors that of the authors in this article. DECT image quality is very much better with the current reconstruction software. It now rivals SECT in image quality and is the same in radiation dose. But tissue characterization is better and iodine contrast is much brighter – you may need much less injected contrast (up to 70% less).
This interesting article documents both the degree of CT dose reduction from model-based iterative reconstruction and improvement in image quality when looking at lung parenchyma detail.
This study further validates that model-based iterative reconstruction can decrease CT exam dose by 50-80% without compromising diagnostic power. There now is a substantial accumulation of published reports of this type in multiple body areas and organs. The same is becoming true for blended types of adaptive statistical plus model based (minus the optical components) iterative reconstruction (such as ASIR-V).
This study published online February 13 in Radiology discusses information patients want before they have an imaging exam. Many look for information about the procedure on their own before their exams, and about 20% have not received any information from their healthcare provider in preparation for the imaging.
The preferred source for information about imaging exams is the referring provider. For this reason, radiology providers should reach out to referring providers with educational resources for patients. Most patients want to know how to prepare for their exam.
RadiologyInfo.org is an important online resource jointly sponsored by RSNA and the American College of Radiology (ACR). This resource contains information on various imaging exams for patients. Not only is information presented in an easy-to-understand format, but there are also videos of radiologists explaining common imaging exams.
GIGO applies here, but with much greater consequences. Conversely, good information in results in more valuable consultation out in the form of the Radiology reports. See this article for how the authors “found improvement in quality of histories provided on requisitions for unenhanced head CT after a fairly simple intervention in the ED. In addition to aiding interpretation, improved clinical information significantly reduced time in receiving payment for the studies.” This results in a “win” for all, including likely improved quality of care for patients.
This study illustrates how iterative reconstruction techniques can be used to lower the radiation dose when using CT to search for urinary tract stones – without compromising accuracy significantly.
Its time has come!
In this era when spoken English can be translated into heard French in real time by an app, perhaps translating radiologists reports into lay language (as demonstrated by this article) might also be accomplished – also in real time. Patients would love to have this ability, and it would serve to better engage them in their care.
The authors raise this question from a patient-centered approach: “What would patients choose if given the option to drink or not drink oral contrast material, and why? Some patients might prefer a risk-averse approach and prioritize diagnostic accuracy, whereas other patients might prefer a comfort-based approach and prioritize examination comfort. Asking patients how they value these trade-offs can inform an optimal imaging strategy.”
Modern oral contrast (diluted Omnipaque) is tasteless and odorless. Most patients think they are drinking water. But, it significantly increases diagnostic accuracy, particularly in cases involving GI questions.
These authors concluded, “If oral contrast material has any diagnostic benefit, most outpatients (89%) would rather drink it than accept any risk for missing an important finding.”
This excellent research from UCSF documents that education about best CT dose practices has a significant impact. The authors state, “The project strategy was to collectively define metrics, assess radiation doses, and move toward dose standardization. This article presents the results of our efforts using a combination of facility-level audit and collaborative efforts to share best practices.”
In this article, the authors discuss how awareness of dose and risks of medical imaging by patients can facilitate shared decision making and reduce unnecessary radiation exposure.
Kalpana M. Kanal, Ph.D., a medical physicist, professor and section chief in diagnostic physics in the Department of Radiology at the University of Washington School of Medicine, Seattle, and colleagues examined actual patient data from the American College of Radiology (ACR) CT Dose Index Registry to develop size-based DRLs that enable healthcare facilities to compare their patient doses with national benchmarks and more effectively optimize CT protocols for the wide range of patient sizes they examine.
The use of DRLs have shown to reduce overall dose and the range of doses observed in clinical practice.
Dr. Kanal’s research is published here in Radiology.
This landmark work is very helpful in benchmarking CT dose levels. It will be widely cited, I predict. Congratulations, Kalpana!
Kalpana M. Kanal, Ph.D.
In this article, the research conducted by University of Washington Radiology Fellow Dr. Achille Mileto and colleagues highlight the importance of dose monitoring, but also the challenges: “Successful efforts to reduce overall radiation doses may actually direct attention away from other critical pieces of information that have so far been underappreciated, namely the widespread variability in global radiation dose values across clinical operation volumes.” … “These data may provide a foundation for the future development of best-practice guidelines for patient-specific radiation dose monitoring.”
Dr. Achille Mileto from the University of Washington
“We are kind of obsessed with radiation dose reduction, but I think we should keep in our minds the concept of radiation dose optimization, which means trying to adjust the dose to the specific clinical task,” Mileto said. “With technology we are reducing the dose, but we are increasing the room for variability. This is great if you are consistently reducing the dose, but we really want to understand what’s going on in terms of variability. So I think the main lesson is to try to develop best-practice guidelines for patient-specific radiation dose monitoring. I think basically the scenario in the near-term future will be to create some kind of shared library for radiation doses.”
This article highlights the wide variation in CT patient radiation dose between similar institutions for similar exams. Recent analysis of ACR dose registry data also suggests there is wide variation amongst different regions of the country.
Such variations suggest that attention to the details of CT technique and technology can produce CT exams at much lower dose – presumably without compromising diagnostic power.
This recent article from Radiology reports the use of an 80% reduced dose CT protocol for assessing moderate to high risk patients for ureteral stones in an ED environment.
Reduced dose CT was correct for stone versus no stone in 100% of 108 patients. Dose reduction was achieved by lowering both the mAs and the kVp and adding iterative reconstruction.
Using model-based iterative reconstruction, CT colonography can be a very low radiation dose method of screening. This article applauds the United States Preventive Services Task Force (USPSTF) approval, cited as a “big win for patients.”
This article illustrates how iterative reconstruction can be used to markedly lower CT radiation dose without significant impact on diagnostic content in CT exams.
For patients with Crohn’s disease who likely will have multiple CT exams over time, lowering dose is especially important.
Study concludes that ultralow-dose CT may substitute for standard-dose CT in some COPD patients
There are at least three different generations of iterative reconstruction, all of which enable substantial CT dose reductions without compromise of diagnostic power. While earlier versions of IR yielded 30% dose reductions, those with model-based IR or some blend thereof can result in 50-80% patient radiation dose reductions – with even better spatial and low contrast resolution. Access the full article on this study.
As this article demonstrates, iterative reconstruction is a very powerful way to reduce dose without impacting diagnostic ability. Key points of the authors include, “To reduce patient and operator radiation dose involves optimization of medical imaging equipment and best control of the equipment by the operator. … The results of our study confirm in a large patient number reflecting the routine clinical setting that the image noise reduction technology allows a significant reduction in radiation dose. … The substantially lower radiation dosage achieved in a routine clinical setting with the image noise reduction technique, provide further evidence of the substantial impact of the new technology. They indicate potential reduction in radiation dosage in invasive and interventional cardiology with more diffusion of newer radiation technology in clinical practice.”
All iterative reconstruction techniques powerfully reduce CT radiation dose in the 40-80% range – without compromising diagnostic power. And they all continue to be refined and to evolve, as this article illustrates. While the “look” of CT images may change from the noise removal, the diagnostic power is not compromised despite the substantial dose reduction. As radiologists, working with change is our future. The old days of nothing but filtered back projection are in our history but not in our future.
This article provides another neat bit of knowledge to consider when looking for lowest dose – though this is multi-factorial.
“Rate of backboard use during CT examinations of the chest–abdomen–pelvis performed in the ED from 1 January 2010 to 31 December 2012 (n=1532). Note the dramatic drop in backboard use in 2011 after multidisciplinary implementation of a policy for prompt removal of patients from backboards using primary clinical survey rather than waiting for a CT examination.”
Guest blog by Kalpana M. Kanal, PhD, Director of Diagnostic Physics Section and Professor in the Department of Radiology at University of Washington
In a recent article published online1, the authors state in their introduction that radiation dose risk is cumulative and an increasing number of patients are undergoing multiple follow-up procedures at regular intervals. Is cumulative dose of concern in patients who have repeated scans? The jury is still out on this question. There is support for tracking cumulative dose2 as well as thought that cumulative dose should not be given any importance when making decisions about individual patients3, 4.
Radiation risk is based on the linear no-threshold model which states that all radiation exposure carries some risk but these need to be weighed against the benefits of the radiation exposure. This linear relationship implies that irrespective of which CT scan a patient is receiving, the absolute risk is the same. There is no increase in sensitivity from the increasing dose received from repeated CT scans, only an accumulation of probability. The linear no-threshold model would break down and not make any sense if there was an increase in sensitivity from repeated scans.
Consider the analogy of driving to work every day which has a risk of a fatal automobile accident associated with it. We do not keep track of the number of times we have driven in the past and its influence on whether we drive tomorrow or not. Similarly, as far as medical decisions are concerned, cumulative dose should not play a factor in deciding if a CT scan should be ordered or not. The benefit of getting the CT may far outweigh the risks. Also, individual risks are hard to quantify as all our risk models are based on large population data.
It is very important that we do not misuse the patient history information about previous scans to influence our medical decision today. Educating the physicians and the public on this is paramount to avoid such misuse.
- Roobottom CA and Loader R. Virtual Special Issue Radiation dose reduction in CT: dose optimisation gains both increasing importance and complexity! Clinical Radiology, 2016; 71(5): 438–441.
- Sodickson A, Baeyens PF, Andriole KP, et al. Recurrent CT, cumulative radiation exposure, and associated radiation-induced cancer risks from CT of adults. Radiology 2009; 251: 175-84.
- Durrand DJ, Dixon RL, Morin RL. Utilization Strategies for Cumulative Dose Estimates: A Review and Rational Assessment. Journal of the American College or Radiology 2012; 9: 480-485.
- Eisenberg JD, Benjamin Harvey HD, Moore DA et al. Falling Prey to the Sunk Cost Bias: A Potential Harm of Patient Radiation Dose Histories. Radiology: 2012; 263(3): 626-628.
To quote the American Association of Physicists in Medicine:
- The risk from medical diagnostic radiation in doses below 50 mSv as a single dose or 100 mSv as a cumulative dose is too small to be measured and may be non-existent.
This article illustrates two key points:
- CT information is particularly impactful in the ER environment where they need correct diagnoses quickly in order to initiate therapy and triage patients safely from crowded facilities.
- Dual energy CT provides incremental diagnostic information in the ER setting but without any incremental radiation dose – so using it routinely for certain indications may be effective.
There is no question that a radiologist who consults directly adds substantial value for both referring physicians and patients. As we make exams more appropriate, we should probably plan on spending more time as consultants and meet the patients, as this article explains.
Pictured above: UW Medicine Radiology Chief Resident Jennifer Favinger and Resident Derek Khorsand consulting with patients at the Seattle/King County Clinic
Images courtesy of UW GME
This article illustrates how much good diagnostic information can be obtained using very low CT radiation doses when screening for lung nodules.
In the screening environment, doing no harm is especially important since so many patients are screened. But detection rates cannot suffer.
Here is encouragement that we can meet both goals with very low dose CT combined with iterative reconstruction.
This article pretty well confirms what many have felt: model-based iterative reconstruction (MBIR) lowers radiation dose by 70-80% compared to adaptive statistical iterative reconstruction (ASIR), without loss of diagnostic power/information. While the images do indeed look different because there is much less noise and because of a slightly different pattern in the remaining noise, all the findings are there. Further, the anatomy and the findings are displayed as well or better.
So, in a young patient (under age 45) – especially if they are likely to be getting multiple exams – use of model-based iterative reconstruction is well worth the longer reconstruction time.
(To read more about CT enterography, Radiologyinfo.org is a great resource for patients.)
Paying attention to limiting Z axis coverage yields big dose saving dividends! See this article for results of this study designed to assess the safety and efficacy of radiation dose reduction in hospitals lacking iterative reconstruction.
This comprehensive article demonstrates the importance of CT dose monitoring and utilizing strategies to achieve ALARA (as low as reasonably achievable) doses while maintaining image quality for optimal clinical diagnosis. The authors also describe how the use of technology can improve the radiation dose efficiency of CT scanners.
Guest blog by Kalpana M. Kanal, PhD, Director of Diagnostic Physics Section and Associate Professor in the Department of Radiology at University of Washington
At the AHRA conference in Las Vegas recently, Dr. Pizzutiello, a medical physicist, discussed the complexity of CT radiation management and monitoring in diagnostic imaging. With the growing use of CT exams being performed and radiation dose in CT being a hot topic in the radiology community, it is imperative to monitor radiation dose from the CT exams as well as observe trends over time. Regulations now require that CT dose has to be documented and available on demand, CT protocols be revisited on an annual basis and incidents with high dose CT exams be reviewed. Several states around the US have CT regulations or are in the process of regulation implementation. It is a monumental task to monitor and manage dose, especially for large hospitals.
There are several dose management software products available that can help in managing the dose. Dose management is, however, a team effort and it is not possible to do this effectively without a team of radiologists, technologists, and medical physicists participating in this important task.
At our institution, we have been managing dose using a commercial product, Dose Watch (General Electric Healthcare) and also have a radiation safety committee within the department to review dose trends and make intelligent decisions based on our dose data. We have also been participating in the ACR CT Dose Index Registry since its inception and review our trends and benchmark values to our peer institutions. This is definitely a good idea if one is unaware of dose trends at their institution and how it compares to others around the nation.
Dose monitoring is complex but a necessary patient safety tool and, if well planned, can be accomplished and maintained with the help of dedicated professionals who understand the importance of the task.
At UW Medicine, we use a dose alert system built into DoseWatch (GE Healthcare) as well as in the individual CT scanners. While this is a good safety mechanism to prevent accidents and notice high dose exams, it’s not the whole answer. As this article points out, “… in practice, CT technique and therefore patient dose depends very much on patient size.”
Size specific dose exposure (SSDE) is a better measure which we will be hearing more about in the near future.
This article highlights that it is possible to achieve much lower radiation dose CT scans for commonly employed types of CT studies – the CT for urinary tract stones is one of the most common.
While not done everywhere, attention to detail can produce remarkable reductions in patient radiation without compromising diagnostic power.
Use of a lower kVp will actually make stones a bit brighter.
Careful attention to patient centering in the gantry can make a difference of up to 40% in dose.
And the use of iterative reconstruction techniques is now widely accepted to not compromise detection, yet with marked dose reduction – whether it be statistical iterative reconstruction, model based iterative reconstruction, or some blend of the two.
Radiologists and technologists both need to understand the importance of these tricks and the physics behind each.
This interesting paper talks about the use of iterative reconstruction to help lower the radiation dose of screening CT colonography.
Of course, as with all screening exams, the first order of priorities is to do no harm – hence the motivation to keep the radiation dose especially low.
The challenge is to lower dose without compromising diagnostic power.
For about the past two years, here at UW Medicine (Seattle) we have been using Model Based Iterative Reconstruction (VEO, GE Healthcare) for all our CT colonography exams. As recommended in this article, we also keep the kVp low – 80 or 100, which also helps to reduce the dose.
The result is a very low dose exam, but with excellent image quality and low image noise. This helps to make great coronal/sagittal reconstructions plus very nice 3D fly-through on the post-processing workstation.
Seattle King5 TV’s Jean Enerson reported recently on UW Medical Center’s installation of the GE Revolution CT scanner.
The new technology of the Revolution features the following:
- Much longer and wider detector
- (16 cm vs. 4 cm)
- Much faster rotation speed and scanning
- (0.28 seconds – 70 G’s centrifugal force)
- Much better radiation dose lowering technology
- ASIR-V, auto kVp, density modulated auto mA
16 cm wide-detector array: Whole organ scanning on one 0.2 second rotation
Currently, the Revolution CT scanner is being used at UW Medicine for scans of the heart, blood vessels, and organs that involve more than one pass and the evaluation of transplanted organs. In the future, we intend to expand further into:
- All aortograms
- coronaries, perfusion, congen., ablation
- All misc. vascular studies
- Renal arteries, HA, runoffs, carotids, COW, grafts/stents, venograms
- Non-Dual-Energy multi-pass exams
- Liver, pancreas, IVP
- Perfusion (brain, transplants, tumor)
- Workhorse (CAP, KUB, brain, spine)
This article illustrates that Radiologists’ perceptions of image quality and content change as they become accustomed – over time – to the different noise pattern of the various types of iterative reconstruction.
In fact, no spatial resolution or low contrast resolution is lost with iterative reconstruction techniques – and diagnostic power is maintained.
Our work here at UW Medicine agrees with this report.
And it is important to know this because iterative reconstruction can result in 30%-60% dose reduction for all types of CT, without loss of diagnostic power.
This is a major advance as American healthcare evolves from reactive to preventive.
But a key to success in this lung cancer screening program is keeping the radiation dose of each exam as low as possible – certainly well below one mSv. Ideally, a low dose approach would involve model based or some other form of iterative reconstruction. All the other techniques to minimize dose should be employed together. Fortunately, this is an application where very low kVp will work well (70-100).
Next – and possibly even more impactful: coverage for screening CT colonography.
This article outlines the substantial reduction in radiation exposure to body parts which are shielded during a CT scan but not included in the field of imaging.
That is a very good practice.
More controversial is another practice: shielding sensitive body parts which ARE included in the field of imaging, specifically breasts, thyroid and gonads.
For some types of scanners this works well, while for other types less well.
With our scanners (GE) IF shielding to the sensitive body part is applied after the scout views are obtained, and IF the shield is separated from the body by placing towels or a blanket to elevate the shield off the body by 2-3 cm – then this works well. Any artifacts or other issues with image quality are minimal or out of the area of interest and the dose to the shielded body part does drop measurably.
Further, such shielding sends a strong message to patients and to our own staff about our concern for their safety.
Here’s a neat trick for dose reduction in appendicitis CT cases – which often are done in young patients.
It falls into the general category of only scanning as much Z-axis length as is needed to address a given indication – and no more.
Guest blog by Kalpana M. Kanal, PhD, Director of Diagnostic Physics Section and Associate Professor in the Department of Radiology at University of Washington
How low can we go in radiation dose without affecting diagnostic confidence for detection of low-contrast liver lesions?
In a recent article we published, we studied the impact of incremental increases in CT image noise on detection of low-contrast hypodense liver lesions. Clinical CT liver exams were obtained on a 64-slice CT scanner using automatic tube current modulation at a routine clinical noise index 15. An artificial image noise addition tool was used to increase the noise level in clinical liver CT images to simulate 75% (NI 17.4), 50% (NI 21.2), and 25% patient radiation dose (NI 29.7) scanning relative to the original images (NI 15.0; 100% dose). The images were reviewed by radiologists of varying experience who subjectively scored lesion detectability on all the images, original and simulated.
We concluded that there is little loss of detection sensitivity for low-contrast liver lesion detectability of CT exams scanned with a NI at least up to 21.2 compared to a NI of 15, a patient radiation dose reduction of 50%. No significant degradation was observed when reader performance was evaluated as a function of lesion size (>10 mm) and contrast (>60 HU) at 90% sensitivity. When lesion size dropped to <10 mm or contrast was <60 HU, sensitivity did drop to 85%.
This study had some limitations, the most important of which was that this study was a simulation and not a true study of CT scanning at lower radiation dose compared to high dose scanning which would have involved scanning patients multiple times. Nevertheless, this study was important as it demonstrated that dose could be reduced by 50% without affecting diagnostic confidence for detecting low-contrast liver lesions.
Guest blog by Kalpana M. Kanal, PhD, Director of Diagnostic Physics Section and Associate Professor in the Department of Radiology at University of Washington
In a recent article, radiation dose was dramatically reduced when technical changes combined with radiation safety initiatives were implemented for adult and pediatric patients undergoing procedures in a cardiac catheterization lab. The air kerma was compared between the first year and the final year of the study. Radiation safety initiatives such as formation of a safety committee, dose reporting and fellow training were implemented into the practice along with technical changes such as reduced dose rates and removal of grid for smaller patients. Considering all procedures, the air kerma decreased by 61% which was significant. For pediatric patients in age range 10-17, the air kerma decreased by 74% which is important as these patients are at higher risk than adults.
This study is important as the patients undergoing cardiac catheterization procedures typically receive high doses and are also potentially repeat patients. This study demonstrated that increased provider awareness combined with radiation safety initiatives, education and technical changes does have an impact on reducing radiation dose.
This is an interesting addition to the sophistication of systematic lowering of kVp during CT coronary angiography. Of course, such sophistication strongly supports 30% dose reduction without compromising diagnostic power.
Since many patients who get CT enterography have repeated exams (inflammatory bowel disease, etc.), Model Based Iterative Reconstrucion has primarily been used to markedly reduce radiation dose while maintaining acceptable image quality.
However, this might be another application – especially if the patient will have only one such exam.
Standardizing dose description parameters and metrics is an ongoing and very active area in ACR and nationwide. This will be a big help to comparing metrics between institutions and over time. The SSDE (Size Specific Dose Estimate) is a good step in that direction.
But this article also points out the large impact of exam appropriateness on dose. It is an impressive fact that a profound way to lower population dose is to avoid doing inappropriate exams. Tools such as the ACR Appropriateness Criteria or Computerized Decision Support at the point of order entry can empower appropriateness review. And every radiologist needs to increase their awareness of exam appropriateness in daily work.
This very wise philosophy for implementing iterative dose reduction in any CT program was well presented at the recent MDCT meeting of the ISCT in San Francisco in June. A key component is to have regular and measurable ways for radiologists to regularly grade or score image quality as dose is ramped down slowly with increasing amounts of iterative reconstruction. With Model Based Iterative Reconstruction (MBIR), it may be possible to drop dose up to 60% compared to otherwise low dose adaptive statistical iterative reconstruction methods (ASIR) – but not in one jump. It takes time to get accustomed to the slightly different look of images with iterative reconstruction.
At least a month’s worth of experience should accrue before passing judgment on image quality. It is also important to guard against anecdotal cases used to render judgments, so experience over time is important. But with a methodical approach, a lot of progress can be achieved in overall dose reduction.
Patients with Crohn’s disease often are young and often have their disease activity assessed repeatedly with CT – though MR is used more frequently now as well.
So – they are good candidates for reducing radiation dose by means of iterative reconstruction.
This paper demonstrates that considerable reduction of dose can be achieved without damaging image quality.
There are some who say that iterative reconstruction should be reserved only for younger patients and not used on older cancer patients who already have serious disease.
But many patients with malignancies are younger or are being treated for cure.
This article suggests that an iterative reconstruction technique (such as model-based iterative reconstruction, MBIR) which can reduce patient radiation dose by 50% may have salubrious utility in patients with lymphomas – who often are younger, who get multiple CT scans, and who are being treated for cure.
This may apply to other malignancies as well.
The ultimate goal is to have a fully informed and well educated patient – this will result in best personalized healthcare and outcomes.
So as far as radiation dose from individual CT exams is concerned, it is good for patients to know what they received – but it is not enough. Patients also need to be educated about the meaning and risk of their radiation dose.
Educating patients about extremely low risk is difficult – as would be true about any very low risk. But, it should be coupled with educating patients about the potential health and healthcare benefits from their CT exam.
This is because what they really need to know is their risk/benefit ratio – from each CT exam. An educated patient who understands their risk/benefit ratio from CT will be a truly informed healthcare consumer.
Who should educate patients about risk and benefit? All of us – all providers. The primary care physician, the subspecialist, the radiologist, the CT technologist, the radiology nurse, PA’s and LPN’s – everyone who contacts the patient can help advance this education and this understanding.
MDCT 2014 speakers weighed in on this subject at the ISCT Symposium in early June.
It is still true that the best way to maximize value and impact on disease while minimizing cost and radiation dose is to do only appropriate exams and not do inappropriate exams. But how to decide what is appropriate? Many of the standard criteria – such as those published by the ACR – are as evidence based as the current peer-reviewed literature evidence will support. But sometimes there may not be scientific evidence available for a hard clinical question – particularly if a randomized trial might be very expensive and take a long time. Under those circumstances, expert opinion is often a pretty good alternative.
Expert opinion can be incorporated into computerized decision support programs but also into daily practice. Indeed, every radiologist is on their own an expert in imaging and its appropriate use – which is valuable if they use this local expertise to guide choice of exams through being a consultant.
Your practice should make radiologist consultation easy to access … and widely known as a valuable service.
See this article.
At the 2014 ISCT-sponsored MDCT meeting in San Francisco – dose reduction was a key theme during all four days.
Iterative reconstruction was a common theme of an overall dose reduction program. While adaptive statistical iterative reconstruction (ASIR) now has been well-shown to reduce average doses by up to 40% without impact on image quality, the hot topic was model-based iterative reconstruction (MBIR) in its various forms.
Consensus is now developing around MBIR being capable of 50-70% dose reductions incremental to adaptive statistical iterations. While image appearance may be somewhat different from that of filtered back projection, it is now pretty clear that such different appearance does not compromise diagnostic power. Indeed, with experience, some radiologists have developed a preference for the image appearance of MBIR.
It is often said that radiation from diagnostic imaging is not an important issue in cancer patients.
But this report suggests otherwise – as expressed by oncologists.
Many patients with cancer are young and/or are being treated for cure. Many have long life expectancies despite having cancer.
And the basic principal of “Do no harm” plus that of ALARA still apply – as much to cancer patients as to any other patient with a serious disease.
So we should be striving for maximal diagnostic information from minimal radiation dose with CT and other modalities in cancer patients, too.
As explained in this study, here’s another trick for reducing both the patient radiation dose and the patient iodine dose in cardiac CTA: lower the kVp to 100 or 80 or even lower.
Of course, you can accomplish this same outcome by using dual energy CT and viewing the vessels with lower keV or kVp while viewing everything else at higher energies.
This article goes straight to the heart of the challenge of tailoring care to each individual patient. Such a tailoring challenge bumps up against algorithmic appropriateness analyses, particularly those which are computerized for decision support. Generalized appropriateness may not ideally apply to individual patients and their unique situations.
How we balance these challenges is to be worked out – to fail at this challenge would be to compromise care, both overall and individually. The coming 5 years will be very interesting for this balance.
This direction of combining a higher noise index (NI) to get lower dose images and then correcting for the resultant noise by using an increased percent of iterative reconstruction (ASIR) is exactly the way to go when striving towards “as low as reasonably achievable” (ALARA) – in my opinion.
At UWMC, we have for a couple of years now gone even further – we use NI in the 30-36 range and routine 70 percent ASIR as a standard for all our CT imaging except high resolution lung (which is NI 25 and ASIR 30%). According to the ACR CT Dose Registry, we are in the bottom 10% of their data base for CT dose….. but the images are very good.
Check out this article to learn more.
CT to search for urinary tract stone is a very commonly performed procedure because both negative and positive results may have significant impact on subsequent patient care. Often the patients are younger since stones can occur at any age.
This article presents very encouraging news about significantly lowering the dose of a CT for urinary stones by using statistical iterative reconstruction – yet with acceptable image quality and no loss of diagnostic power.
This report adds to a rapidly growing body of data about both statistical iterative reconstruction and model based iterative reconstruction for various types of CT exams. This body of data almost uniformly reports substantial patient radiation dose reduction in the 30% to 60% range with equal or even better image quality.
For the question of whether lung cancer screening in high risk patients causes more good than harm, check out this article.
I’m pretty convinced the data shows that in a research study high risk population where the scans are read by highly skilled experts closely following the rules, lives are saved by CT screening and the cost is reasonable for each QUALY.
Further, the interpretation of these chest CT screening exams is fairly straightforward for experienced and trained radiologists. That suggests that when CT screening is extended beyond research to broader community practice, results should also be good.
We already know that low-dose CT is a valuable tool for reducing mortality rates, but now there’s evidence that it might reduce financial costs as well. A new analysis of the 2010 National Lung Screening Trial (NLST) shows that low-dose CT is a cost-effective diagnostic tool for patients at high-risk of lung cancer, according to AuntMinnie.com.
The Medical Imaging and Technology Alliance (MITA) released a statement saying the organization welcomes the analysis and “looks forward to ongoing collaboration with patient advocates and others in the imaging community to ensure access to this lifesaving technology.”
In my opinion, though, the key question in whether low-dose screening for lung cancer is cost effective is: what is the cost of working up the false positives? That cost needs to be subtracted from the cost benefit of the lives saved. This new analysis suggests that low-dose screening is indeed cost effective. One thing no cost analysis considers: the value of a negative exam to a very worried patient.
Further new twist: we now can do ultra-low-dose lung cancer screening using fully model-based iterative reconstruction techniques. This technique enables a 60 percent radiation dose reduction (down to the sub-0.5 mSv range) below that of even recent low-dose CT – further substantially decreasing any downside from lung cancer screening in high-risk patients.
A University of Washington study featured in the August issue of JAMA Pediatrics claims that 4 million annual pediatric CT scans of the head, spine, abdomen and pelvis are predicted to cause nearly 5,000 future cancers, according to HealthImaging.com. However, the study goes on to state that the risk can be mitigated by CT dose reduction and appropriate imaging initiatives which have the potential to prevent more than half of the projected radiation-related cancers. Practices like eliminating unnecessary scans and targeting high-dose scans are called out in the study.
I believe that the best way to reduce radiation dose from CT in children is to not do studies which are inappropriate or which have a very low chance of producing impactful diagnostic information. The next best way to reduce dose is to pay close attention to all the tricks of technique: accurate patient centering in the gantry, use of radiation shields, use of 80 or 100 kVp, minimizing Z axis scan length, etc. Then newer technology will greatly further reduce dose – automated tube current modulation, iterative reconstruction – especially fully model-based iterative reconstruction. Together these can reduce radiation dose by 70-80 percent. Scanning in kids above 6-8 mSv should be a thing of the past and sub-1.0 mSv scans should be common.
The following passage, from an article on HealthImaging.com, caught my attention:
The honeymoon has ended for coronary CT angiography (CCTA) and the seven-year itch has commenced for some radiologists and cardiologists. They do not advocate replacing the technique though. Rather, they are asking if the requirements in training guidelines need a makeover to reduce variability and better maximize CCTA’s potential to improve patients’ clinical care and outcomes.
This brings up a good point: the credentialing criteria for performing and interpreting cardiac CT are now too low. I found the learning curve was long with a gradual slope. You need to be in a training and supervised environment with a fairly good case load for at least a year. It’s challenging, but performed well and interpreted with skill, it is a very valuable test which can save the healthcare system considerable cost – especially in low- to moderate-risk chest pain patients presenting to an emergency room.
A recent study featured in the Journal of Computer Assisted Tomography touches on the perennial issue for radiology researchers studying and evaluating the effectiveness of different low-dose protocols. The topic brings the need for accurate CT dose reporting to the forefront, as researchers use different techniques to compare dose levels without relying on unnecessary CT scans in the same patient.
At the Mayo Clinic, researchers have used iterative reconstruction to acquire half-dose virtual colonoscopy exams to compare with full-dose exams. Previously, radiological researchers have relied on phantom studies to approximate dose differences among different protocols, or on patient division, in which patient groups (that are similar but never match precisely) undergo different scan protocols to approximate dose differences.
The issue, however, is that radiation dose and image quality must be compared in every patient, not just groups, because discrepancies in patient shape, cardiac output, lesion pathology, and other factors are highly individualized. The study continues, “matched-cohort research studies can’t evaluate the impact of noise reduction on reader performance for identifying findings, and even back-to-back full- and half-dose studies cannot control for the effect of phase enhancement on lesion conspicuity.”
Both of these points are valid. But, there is hope in the form of positive scientific studies on the way. Research from the University of Washington will soon be published in the American Journal of Roentgenology involving patients with cirrhosis and hypervascular liver tumors. This research offers valuable information for the future of low-dose CT reconstructed with multiple techniques from the same data set when comparing lesion detection.
Additionally, research involving the challenge of scanning the same patient twice with two different dose levels is ongoing. The Institutional Research Board has approved this study at a number of institutions, which analyzes patients who are scanned with ASIR and then full-iterative techniques. Stay tuned for full data available next year.
While these challenges do indeed exist, these ongoing studies offer hope for the effectiveness of low-dose protocols and understanding which protocols work most effectively.
The American College of Radiology’s (ACR) CT Dose Index Registry (DIR) program was introduced in May 2011. The DIR is a data registry that allows institutions across the United States to send their anonymized CT exam dose information to the ACR to be saved in a database at ACR. Institutions are then provided with semi-annual feedback reports comparing their results by body part and exam type to aggregate results for adult and pediatric exams. Facilities can then compare their CT dose indices to regional and national values.
At UW, we enrolled in the DIR in May 2011 and since then have been sending encrypted DICOM structured dose report files from all of our CT scanners to ACR. Doing so required collaboration between ACR, IT, PACS personnel and the on-site physicist. Implementation involved several challenges, including software installation and data transmission consistency problems. Since numerous institutions are involved, the ACR required an exam mapping process via the Radlex Playbook to unify the protocol classification. This mapping process has been the most challenging factor in the implementation process. These challenges have been overcome and data is being successfully transmitted to and analyzed by the ACR.
The first report comparing adult patient dose data (CTDI and DLP by medical examination and by scan) between our site and others around the region and country was made available in January 2012 and the second one in September 2012. For each exam, the report includes box-plots and histogram data for a variety of standard protocols. The second report estimated the size specific dose estimate from the scout for each patient exam.
The ACR CT Dose Index Registry program has been very successful and is a useful tool for dose data mining and will eventually establish national benchmarks for CT dose indices.
For more information on the Registry, please see this article here!
A few weeks ago, the New York Times featured an article, “Medical Radiation Soars, With Risks Often Overlooked.” The article brought up some valid points about radiation, but also requires readers to take a step back when processing some of the information given.
Yes, as the article ascertains, radiation has its indisputable medical advantages, in addition to its potential medical downsides. The amount of medical imaging, including CT scans, has significantly increased over the last few decades, as more life-saving procedures are discovered and as technology develops. As a result, some patients are subjected to higher levels of radiation, which, according to this article, is “believed to account or 1.5 percent of cancers” in the United States.
The piece goes on to say that “the cancer-causing effects of radiation are cumulative” and that doctors and hospitals fail to track the amount of radiation patients have already been exposed to when ordering a new exam. While it is critical to practice “As Low As Reasonably Achievable” (ALARA) for every protocol and to closely scrutinize every exam request for appropriateness, there is absolutely no evidence that risk from well spaced CT exams is cumulative. Therefore, canceling an otherwise appropriate exam because of cumulative dose may not be in the patient’s best interests. For all CT exams a risk/benefit evaluation should be made by a well informed radiologist. For the existence of multiple prior exams alone to change the risk/ benefit ratio would be extremely rare.
Additionally, the claim that “no one” keeps track of how much radiation patients have been exposed to is inaccurate. A number of institutions, including UW, are a part of the American College of Radiology’s Dose Index Registry, a program striving to accurately track CT radiation dose in order to establish benchmarks, monitor patient radiation dose exposure, and compare patterns. More recently, a pediatric dose registry was introduced to perform similar functions, but for a younger demographic.
Both doctors and patients should be as informed as possible when it comes to radiation. Understanding the risk/ benefit ratio is an important part of this—and no appropriate medical imaging exam should be cancelled if it will benefit the patient, especially if its radiation level is ALARA.
In July’s Radiology, a new study was featured that suggests that a new pill can prevent DNA damage that might lead to cancer. Researchers analyzed DNA double strand breaks (a precursor lesion to cancer) before and after X-raying human blood that had been mixed with the pill, a compound of antioxidants and glutathione-elevating agents.
At this point, the most common way to prevent radiation damage, which can damage the DNA, is lowering the radiation dose level and exposure time, shielding, and staying away from radioactive sources. However, further research may prove that this pill could be an additional way to prevent radiation damage. According to this study, there was a 58 percent reduction in double strand breaks from subjects who ingested the compound one hour prior to imaging.
The idea is in its first stages so it remains experimental and esoteric, but my esteemed colleague, James Brink, MD, from Yale has done an analysis of the research. He says:
“The study was very exciting from a methodological standpoint. I was impressed with the methods by which the authors were able to assess the formation of double strand breaks in response to low doses of ionizing radiation using the fluorescent tagging technique.
I’m respectful of the challenges, but without a clear-cut identifiable clinical benefit, we only have a laboratory benefit. While many lab studies on the biochemistry of antioxidants have been encouraging, some clinical studies have not shown antioxidants to be beneficial to subjects. That’s why we’d want to be cautious about jumping the gun.”
Though additional research must be done to assess the widespread benefits of the use of this compound prior to imaging, its potential benefits could be great for radiation damage reduction.
“Don’t Skip the CTA” that’s the word going out to patients with advanced renal failure based on findings of researchers in Baltimore. In a study presented at June’s International Society for Computed Tomography (ISCT), Dr. Barry Daly demonstrated how CTA using moderate doses of IV contrast negatively affects only a small percentage of patients and provides valuable information that outweighs the chance of adverse effects.
However, because lower dose is better for patients, especially that small portion at risk with normal doses, Daly and his team also did a study of low-kVp, low-contrast-dose CTA in chronic renal failure patients. This technique is possible due to the advances in CT technology that have allowed radiologists the ability to get more out of smaller amounts of iodine.
While the low kVp techniques enabled much lower doses of iodinated contrast and resulted in images that looked great, the dual-energy CT technique may have accomplished this effect even better!
With dual-energy, you get the best of both worlds. You get the benefit of lower kVp effect (kEv in GE units), plus the ability to look at images which are equivalent to 100 or 120 kVp from the same CT raw data. Essentially, you still achieve substantial iodine dose reduction, but also get very dense HU enhancements in vessels and organs.
The bottom line is this: CTA isn’t something that patients with advanced renal failure should think about skipping. There is a too big a risk for going into surgery without one. The key is finding the safest technique to reduce the dosage level of iodinated contrast while getting the best images. Dual-energy CT may be the best solution out there.
At UW, we are outspoken for our support of adaptive statistical iterative reconstruction (ASIR). As a big proponent of the method, I find this write-up from Radiology to be a landmark article, and the research it highlights, very impressive work.
A team of researchers recently confirmed that iterative reconstruction allows significant CT radiation dose reductions for patients undergoing urolithiasis imaging, without unintended decreased image quality or diagnostic confidence.
Urolithiasis is a common condition, with high likelihood (estimated at 75 percent) of recurrence amongst individuals diagnosed. Therefore, imaging scans are a regularity for those patients with the disease. It is important to treat these patients with the lowest radiation dose possible, as to alleviate fear of potentially excessive radiation.
For the 25 patients involved in the study, image quality was significantly boosted by adding iterative reconstruction, while dose was reduced by about 85 percent, thanks to the ultra-low dose. While previous studies report substantial degradations in imaging quality, 80 percent of the images acquired in this study had suboptimal image quality.
This study is just further evidence of the promising benefit of ASIR. I firmly believe that every imaging site with access to the protocol should use it regularly as to lower dose by 80 percent in frequently performed exams.
To learn more about iterative reconstruction, please click here!
A new risk model for lung cancer was recently highlighted in the August 21 issue of Annals of Internal Medicine. According to the report, the Liverpool Lung Project (LLP) risk model was developed to determine, based on specific and sophisticated assessments, which individuals would benefit most from CT lung screening.
The LLP risk model has a strong ability to predict lung cancer, and, according to principal investigators, does so better than smoking duration or family history. In fact, this data has been confirmed by researchers from the University of Liverpool, as well as several U.K. centers, the U.S. National Cancer Institute, and the Harvard School of Public Health.
Unlike some other major diseases, like breast cancer and heart disease, lung cancer, thus far, has lacked adequate identification tools to determine which patients should be targeted to maximize screening benefits, and minimize its potential harms. Identification of those with the highest risk for lung cancer, a disease which now kills upwards of 1 million annually, will make the best use of the benefit-harm ratio.
Though other risk models have been created, none have been able to successfully apply to all of the world’s population. The LLP could overcome these challenges, though, as it accounts for important risk factors that others skip, including history of pneumonia, non-lung cancer, and asbestos exposure, among family history and smoking history.
The model certainly appears a good way to improve patient selection. As always, the key inscreening exams is to do no harm. Even for those patients deemed appropriate for screening by the LLP, the best approach is with ultra-low dose CT— such as done with model based iterative reconstruction.
To learn more about the LLP, please click here!
At the recent International Society for Computed Tomography (ISCT) annual meeting, held in San Francisco, Dr. Eliot Siegel, from the University of Maryland, discussed an evolving technique for CT dose-reduction. This application does not focus on simulated image noise as a measure of image quality, but instead, works to more accurately depict that noise in low-dose CT scans. In other words, this technique aims to optimize dose based on what the radiologist needs to see.
According to the presentation, the future of low- dose optimization will rely on a combination of the visual perception system and sophisticated mathematical models designed to minimize the dose for every imaging exam without impairing the quality of the image to the radiologist. In fact, the current methods for low-dose optimization are already on the way out as awareness for radiation dose continues to evolve.
Dr. Siegel’s analysis of noise in the new world of iterative reconstruction is very sophisticated and thoughtful. Concepts of pink and white noise plus just-noticeable differences really are cutting edge. These ideas will clearly advance our understanding of how to get a world of fully automated dose minimization.
Dr. Siegel and his team of researches, as usual, are thinking profoundly and in very innovative ways. These concepts certainly raise great hope for a much more systematic future combined with much more sophisticated math to make patient doses even lower than we had previously dreamed! It will be an exciting next three years for dose reduction techniques and technology!
The topic of cardiac CT credentialing came up at the recent International Society for Computed Tomography meeting and raises interesting points on the specialized training. Some wonder with the comprehensive residency and fellowship training that’s required to earn the title of “radiologist”, just how necessary this special credentialing for cardiac CT is. Dr. U. Joseph Schoepf of the Medical University of South Carolina points out that it is essential and ideal for cardiac imaging.
Schoepf notes, “The truth is that cardiac CT is the new kid on the block for many practitioners who finished their training more than a decade ago.” He went on to say that anyone who wants to read cardiac CT needs special training, but “there aren’t enough institutions out there that have enough volume in cardiac CT to really appropriately train residents and fellows.”
Dr. Schoepf is 100 percent correct. Cardiac CT requires relatively extensive subspecialty training plus a fair amount of experience for proficiency. Even a Board Certified Radiologist can’t pick it up overnight or at a weekend course.
Subspecialty certification and re-certification after an appropriate time are very good initiatives. A Certification of Added Qualification (CAQ) in cardiac CT is just as meaningful as one in Pediatric Radiology or Interventional Radiology. It provides some assurance about a radiologist’s level of knowledge and practice excellence.
To read more about the importance of experience when it comes to CT, please click here.
At a recent Society for Pediatric Radiology (SPR) meeting in San Francisco, one presentation addressed low-dose CT’s “bright future, but troubled present.” Texas Children’s Hospital’s Dr. R. Paul Guillerman touched on the many uncertainties and challenges involved in low-dose radiation optimization, citing that these goals are so complex that they may nearly be impossible.
But, let’s take another look at this. Yes—dose reduction is complex and full of potential traps leading to poor technique or image quality. However, that is not a reason to avoid implementing a dose reduction (technique optimization) program at your institution!
So, how do you lead your institution down a road towards dose reduction? First, start with Google. Read what you can find on the topic. Then, go to meetings, talks, and presentations given by experts with considerable experience in the endeavor. Finally, start at your own institution.
I would suggest trying one variable at a time. Implement a weight based (or cross-sectional area based) kVp selection program. Then, embark on understanding how to use weight (or BMI) based selection of Noise Index for automated tube current modulation. Don’t forget to check out the easy stuff – like patient centering, use of bismuth shields, and limiting Z axis. Realize that even your contrast injection protocols – volume, rate, blending – might benefit from a weight based approach. Decide how to implement iterative reconstruction, varied by body region.
With these steps you are set to embark on a continual journey. Get started… today!
Pediatric radiation dosage continues to be a hot topic in the news. Just recently, a new team of researchers stepped out with a goal of reducing overall radiation exposure level for pediatric patients. The team, called the Quality Improvement Registry in CT Scans in Children (QuIRCC), is made up of researchers from six children’s hospitals and is currently in the process of researching and developing the first pediatric CT dose index registry.
The QuIRCC comes after a May 9 mandate from the U.S .Food and Drug Administration (FDA) requiring manufacturers to design scanners with young patients in mind, intended to reduce overall radiation exposure levels in pediatric patients. However, the QuIRCC project is about more than just manufacturing. In fact, the project is designed to help “child-size” scanning protocols by offering accurate metrics to measure radiation exposure in children.
The development of such a registry for children, alone, is especially important. But the other important feature here in this project is establishing the target ranges of dose per exam type that are considered acceptable. This should lower or damp down the large range of variance in dose for similar exam types between nearby medical centers.
Here at UW we know the importance of dose registry programs, as we got involved in the American College of Radiology Dose Index Registry pilot project right away. This new dose index registry will make great strides for ensuring safe radiation practices for patients of all ages.
A new pediatric imaging study has been making headlines, but it’s important for patients to keep in mind both the risks and benefits of CT scans when evaluating the research. The study, published this week in Lancet, a British medical journal, claims that CT scans expose children to cancer causing radiation.
According to the researchers, for every 10,000 CT scans performed on children under the age of 10, one additional child will get a brain tumor and another child will get leukemia within 10 years of the initial scan. The research claims that these cancers would not have otherwise been expected regardless of medical imaging exams.
However, this article documents an extremely small risk. In fact, this figure is less than what we have been assuming historically prior to any evidence. But, the article also cautions that any decision on whether or not to scan should involve a risk/ benefit ratio consideration. The study does not change our assessment of risk in that ratio. Thus, the potential benefit from CT remains the critical determinant on whether to perform a scan.
As always, the ACR appropriateness guidelines help with that assessment. That also is the role of trained Board Certified radiologists—to know and advise about when CT scanning creates a risk/ benefit ratio strongly in a patient’s favor.
Remember parents, discussing the risks of CT with your health care provider should certainly be done, but be sure to get the full set of facts before refusing care that may save and extend a child’s life.
A new study presented at the American Roentgen Ray Society (AARS) meeting brought attention to another key point in radiation dose reduction. Currently, a majority of the focus on cutting CT scan radiation is centered on dosage levels, but it is also important to monitor cumulative dosage in patients receiving multiple scans. While government and industry are increasingly focused on single CT scan dosage reduction (which is great news!), there is a lesser concern for decreasing the overall number of CT scans for patients.
The research tracked the amount of repeated CT exams performed on patients in order to calculate cumulative radiation dosage. Some of the results are shocking. The study identified a group of patients from the test population undergoing more than 20 medical imaging exams in one year, and as a result, being exposed to high cumulative dosage—more than 300 mSv per annum! In fact, one patient received 70 different scans in one year!
This is, of course, something we are working to mitigate continuously. Europe (EEU) has been tracking the cumulative dose of its citizens for about 10 years—by law! This is certainly a good thing for patients and in the U.S, we are beginning efforts towards this direction. Several products are now available that serve as a repository for dose from devises and particular protocols, to keep track for individual patients (including cumulative).
We recently purchased such a product (DoseWatch, GE Healthcare) which will be integrated with our RIS and connected to every radiation emitting device in our medical center. This product will pick up cases of unusually high cumulative dose in patients, but also identify protocols which have high dose or devices which are emitting high dose. We are looking forward to implementing DoseWatch a few months from now.
Be sure to check back regularly as we document our experience with the product.
That there are strong associations between smoking and emphysema and smoking and lung cancer is well established. Therefore, it’s of little surprise that a report from Lung Cancer finds emphysema that is visible to radiologists from CT scans is correlated with an increased risk of lung cancer.
However, these results were only discovered when the emphysema was read by radiologists— and not by computer interpretation. Researchers point out that radiologists and automated computer software likely detect different types of emphysema- with only doctors appearing to detect the type of emphysema associated with lung cancer. This clearly highlights the “intuition” factor in scan interpretation by experienced radiologists—a factor not yet evident in intelligent computers!
Patients that are found to have emphysema detected by CT scans are already at an increased risk of developing lung cancer and should quit smoking as soon as possible. It is interesting to remember that before cigarette smoking became widespread, both lung cancer and emphysema were exceedingly rare diseases. Those high risk patients should explore the benefits of lung cancer screening and lung cancer screening programs.
For more information on the benefits of lung cancer screening, please see here.
Another major organization has joined the U.S. National Cancer Institute to support CT lung cancer screening as a life saving procedure! Recently, the American Lung Association updated its recommendations to support low-dose CT lung screening for smokers and former smokers.
Lung cancer continues to be the leading cause of death in the U.S., with more than 150,000 deaths annually and a five year survival rate as low as 15 percent. However, research from the US National Cancer Institute’s Lung Cancer Screening Trial gives promising hope. The study found that low-dose CT can reduce mortality rates by at least 20 percent among smokers and former smokers. Other published reports have estimated even higher rates of mortality gains! According to the LCST, individuals between the ages of 55 and 74 years who are current or former smokers of at least 30 pack-years and have no history of lung cancer are ideal candidates for lung cancer screening with CT.
Currently, besides never smoking, low-dose CT screening is the only viable option for significantly reducing the risk of lung cancer. The ALA’s recommendation of this medical imaging exam is an important step toward the development of widespread population-based CT screening program through the U.S.
The ALA joins the National Comprehensive Cancer Network, the first major professional organization to recommend low-dose lung cancer screening last fall.
For more information on factors that may effect the widespread implementation of lung cancer screening, see this post on low-cost screening.
Is low-cost an added benefit to widespread lung cancer screening? According to this article, from April’s Health Affairs—yes! The study on this much debated about topic asserts that routine CT lung cancer screening of high-risk individuals would save thousands of lives annually for less than one dollar a month per patient, if implemented throughout the US. According to these figures, the cost of low-dose lung cancer screening could be less than that for both breast cancer screening and colorectal cancer screening.
As we’ve pointed out, lung cancer screening is effective and life saving. For high- risk patients, those who are multiple pack year smokers for 25 years or more, screening provides significant benefits. For these individuals, low-dose CT screening reduces the number of lung cancer deaths by 20 percent!
Despite this, widespread lung cancer screening has yet to be implemented nationwide, largely due to cost. This study reports interesting and encouraging data about widespread implementation of the procedure, though. However, we must remember that there are also reputable articles which report much higher cost numbers when adjusted for quality-life-years saved. It is necessary to take these studies into account, too.
Looks like the jury may still be out on this one!
The Choosing Wisely Campaign is a recent initiative of the ABIM Foundation to encourage physicians and patients to take a second look at tests and procedures that may be unnecessary… and potentially, harmful. The American College of Radiology was one of nine US specialty societies that developed lists of the Five Things Physicians and Patients Should Question.
See the ACR’s outlined recommendations of the procedures that should be utilized less in radiology practices:
• Imaging for uncomplicated headache, absent specific risk factors for structural disease or injury.
• Imaging for suspected pulmonary embolism (PE) without moderate or high pretest probability of PE.
• Preoperative chest x-rays without specific reasons due to patient history or physical exam.
• CT to evaluate suspected appendicitis in children until ultrasound is considered an option.
• Follow-up imaging for adnexal (reproductive tract) cysts 5 cm or less in diameter in reproductive-age women.
All five of these recommendations are ones that I would certainly agree with. In fact, I wouldstrongly emphasize that CT for possible pulmonary embolism in young women be avoided unless there are clinical criteria which raise suspicion to at least moderate level. Additionally, ultrasound is a great modality to check for appendicitis in children, especially those that are young and/ or thin.
For the full recommendations by the ACR, please see here. Remember, informed patients are an integral part of the Choosing Wisely campaign.
A recent study on the high accumulation of radiation dosages in young patients with inflammatory bowel disease brings light to a topic of concern for any CT practitioner. This research, published in Clinical Gastroenterology and Hepatology, concludes that patients with digestive disorders may be exposed to significant radiation doses from abdominal CT over time.
It attests that the radiation levels among patients with gastrointestinal disorders have risen over the last few years. And, mostly due to repeat scanning, over 50 percent of the patients with cumulative exposure exceeding the 90th percentile, particularly those with IBD, were younger than 35 years old.
Here at UW, we recently acquired a new CT imaging reconstruction algorithm- VEO or model based iterative reconstruction. This lowers radiation dose 60 to 80 percent below that of ASIR reconstruction and 90 percent below that of FBP. The only disadvantage of VEO? It takes about 30 to 40 minutes per case to reconstruct because it is computationally much more intensive.
In planning how to begin using VEO, one of the first patient groups we’ve focused on is young patients with IBD. The use of this technology will help lower the accumulative radiation dose levels among those patients who require regular abdominal screening.
Most medical equipment is not designed for obese patient optimization, including diagnostic imaging modalities. Due to this, overweight and obese individuals are subject to higher levels of radiation during routine CT scans and X-rays.
A recent study, published in the Journal of Physics in Medicine and Biology, calculated exactly how much additional radiation overweight patients are exposed to from CT scans. According to the research, obese men and women receive 62 percent and 59 percent more radiation during CT scans than normal weight individuals. However, new technology can help control that percentage.
Phantoms, realistic 3-D computer models of overweight and obese men and women, can now be used to determine the risk of radiation scans on different body types. The use of various sized phantoms to study CT dose distribution within the human body is a very scientific approach when considering the effects of CT. This technology will be able to accurately tell radiologists how much radiation patients receive from different devices so that they can make the safest and optimal choice for the patient.
Notice, this article highlights the significant increase in radiation dose—especially in obese patients—from increasing kVp to 140. At UW, our technologists use 140 kVP for CT only after having a conversation with a radiologist about each specific case.
Learn more about the use of phantoms for obese patients here.
According to a new study based on the International Early Lung Cancer Action Program (I-ELCAP), lung cancers identified in low-dose CT screening programs are similar to those identified by non- screening means. The research results, which were released on March 27 in Radiology, further alleviate concerns that cancers detected through low- dose CT screening are less aggressive than those found through other means, and therefore demand less attention and resources. In fact, the frequency of small-cell carcinoma and adenocarcinoma were similar for cancers detected through screening programs and outside the screening setting.
This study is another brick in the wall of evidence building for the value of low radiation dose CT lung cancer screening in high risk asymptomatic smokers. Regardless of whether nodules are solid or “ground glass” (non-solid), growth occurs that is similar in the screened populations and in those detected of having lung cancer due to symptoms.
While it is true we do not yet have a data-based analysis of costs versus quality life years saved, the evidence that screening is worthwhile continues to become stronger. “The CT scanners we have now are really phenomenal,” with resolution that continues to improve as the radiation dose falls, “so that the amount of information you can get out of them for emphysema, for coronary artery risks, and so on, continues to increase,” says Dr. Claudia Henschke, lead author of this study.
She goes on to point out that cancers detected via low dose CT screening “are real cancers that would kill you if they weren’t discovered early, so it kind of underscores again the data that we had shown in ELCAP and that NLST (National Lung Screening Trial) has shown — that screening for lung cancer saves lives.” And that is the key takeaway.
I recently came across a study that questioned the cost- effectiveness of low-dose CT scans for lung cancer screening. As I’ve discussed before, there is sufficient and sound research validating that among high- risk individuals, low-dose lung cancer screening is a life saving process. However, this article claims that the medical imaging procedures may be too costly for the United States, “a nation struggling to control growing health care costs, even though some lives would be saved.”
This article clearly shows how charges relate to the execution of healthcare. At standard charges, screening CT of patient’s at high risk for lung cancer may not be cost effective. But, if these are regarded as add-on incremental cases and are priced at marginal cost (approximately $200), the screening equation may change and become financially viable from society’s prospective.
As with any screening program, the first caveat is to “do no harm” – hence an ultra-low dose CT technique would be advantageous. Similarly, figuring out how to keep the cost way down will be critical. I think we can….
A recent article published in CA: A Cancer Journal for Clinicians states that education of referring physicians, more assertive radiologists, and an increased use of healthcare IT are the keys to reducing patient exposure to radiation.
While these assertions may be true, the article also touched on rising radiation exposure due, primarily, to CT scans. Since the early 1980s, the estimated per capita dose from medical radiation in the US has increased significantly. But this isn’t the whole story…
While it is true that medical radiation from CT has increased markedly since 1980, so has the benefit to health from CT. We no longer do “exploratory surgery” for example, in order to sort out complex diagnostic imaging challenges. The false negative rate from Appendix surgery has plummeted. And cancer diagnosis rates overall are declining while cancer cure rates have gone up substantially, particularly in the last 5 years.
Meanwhile, the radiation dose per CT scan has gone down dramatically as the principles of low-dose CT continue to be better understood and implemented. Scans that used to require 25 mSv of radiation are now being done for 20% of that amount. While negative effects from low dose radiation have never bee proven (below 50 mSv), we still strive to keep our doses as low as possible.
So the issue is not radiation cost, but cost/benefit ratio. Driving a car is dangerous too, but we accept the cost/benefit ration. For CT that ratio is much better!
If you work in radiology, chances are that you are aware of the Image Wisely campaign. Created by the Joint Task Force on Adult Radiation Protection (made up of members of the American College of Radiology and the Radiological Society of North America), the American Association of Physicists in Medicine (AAPM), and the American Society of Radiologic Technologists (ASRT), the campaign strives to lower the amount of radiation used in medically necessary imaging studies and to eliminate unnecessary procedures.
I am proud to say that I have taken the pledge, with over 12,000 other health care professionals, to image wisely by optimizing the use of radiation when imaging patients.
The Image Wisely campaign is a very impactful undertaking which deserves the attention and participation from all of us in Radiology. The pledge raises awareness and commitment to maximizing the ratio between information obtained for minimal dose utilization. In addition, the pledge assists with low dose protocols and good practices, plus equipment operation is included.
I urge all to read the website closely and understand the goals of the campaign. Then take the pledge today!
Research published in this month’s American Journal of Roentgenology reported excellent results on a protocol for working up patients with nodules found in CT lung screening. Ever since the National Lung Screening Trial showed a 20% mortality reduction among high-risk patients screened for the disease, criticism has been vocalized due to the potentially large number of false-positive results following diagnostic imaging investigations. Though the possibility of finding cancer outweighs the risk of false positives, the researchers argued that false-positive results could potentially increase the risks and costs of screening, diminishing the benefit of early cancer detection.
This study, which required participants without a history of cancer to have smoked a minimum of 10 pack-years, concluded with positive results. According to the research, the algorithm produced low false-positive rates, and could make the establishment of large-scale CT screening programs more feasible.
Follow-up CT protocols in lung cancer screening – once a finding is discovered and needs to be evaluated over time or even just routinely on a schedule – is one area ripe for ultra low-dose CT technique. With this technique, we really can see doses reduced by 40 – 80% among these applications! Accepting higher noise in images, very low-dose kVp (in the 80-100 range), and aggressive application of iterative reconstruction techniques can produce diagnostic CT results at breathtakingly low doses.
As the war on cancer continues, a group of U.S. oncologists picked its “Top Five” most essential advances in cancer care, as reported by HealthDay news. I’m pleased to announce that CT-based lung cancer screening is listed as one of the major advances for 2011.
The report, published in the Journal of Clinical Oncology, placed only targeted drug therapy above CT-based lung cancer screening. Both advancements will be major game changers for cancer care. The report confirms that the U.S. National Cancer Institute found that screening smokers and former smokers with a CT chest scan was “dramatically better than the chest X-ray.”
There now is no question about this! In high risk heavy smoker populations, low dose CT- lung cancer screening saves lives… and quite a few. The challenge now is getting our healthcare delivery systems to incorporate this approach into routine preventative medical practices….but only for high risk individuals. We need to make these scans easy to obtain, fast to perform, very low in radiation, covered in health plans, and inexpensive.
The good news is that all of these things are possible. Turning CT-lung cancer screening into a regular practice for in-need individuals is very do-able!
A statement was recently released by the American Associating of Physicists in Medicine regarding how extremely low the risk of harm from radiation in diagnostic imaging studies is. Indeed, they state, it may be non-existent. I am absolutely delighted to finally see a statement like this in print, especially coming from the AAPM, a reputable and dignified organization.
In fact, this kind of statement has been needed for some time:
“Discussion of risks related to radiation dose from medical imaging procedures should be accompanied by acknowledgement of the benefits of the procedures.”
This sentence urges all providers, and even investigative news reporters, to do the responsible thing – discuss risks and benefits at the same time, in a balanced way, using language and concepts that patients can understand and grasp. Understanding extremely small risks (so small as to be potentially nonexistent) is very challenging for most of us – so it requires extra time and effort.
“Risks of medical imaging at patient doses below 50 mSv for single procedures or 100 mSv for multiple procedures over short time periods are too low to be detectable and may be nonexistent.”
Someone finally stood up and said it! The non-detectability of extremely low risk has stood the test of time. The non-existent risk possibility may be true and should be included in any discussion.
“Predictions of hypothetical cancer incidence and deaths in patient populations exposed to such low doses are highly speculative and should be discouraged. These predictions are harmful because they lead to sensationalistic articles.”
It is definitely possible that sensationalism may have resulted in patient harm – by inappropriately scaring some patients away from imaging. These medical imaging treatments might have helped them, whereas not getting the imaging might have harmed them by denying access to the diagnoses leading to correct and swift treatment.
In black and white: predicted cancer risk from these low doses is hypothetical and resultant deaths are only speculation.
The American College of Radiology’s (ACR) Dose Index Registry pilot project has already amassed a number of studies, according to a presentation given at RSNA 2011. The program strives to accurately track CT radiation dose in order to establish national benchmarks, allowing practices to monitor radiation dose exposure and compare patterns. Although only launched in June 2011, the Dose Index Registry is already up and running and any medical imaging facility can now register for the program.
The University of Washington was the second institution to sign up for the ACR Dose Index Registry. Using a DoseWatch product, we will get real time information on every CT scan and every patient scanned, including the dose each machine puts out in general, and dosage each patient is exposed to per scan and over time. This information then gets forwarded to the central registry maintained by the ACR for monitoring and for comparison purposes.
This should be a very powerful monitoring program and a big boost to safety. We are glad to take part in the program and look forward to the insights that being part of the Dose Index Registry can provide!
Recently, the National Comprehensive Cancer Network has come forward in favor of lung cancer screening with low-dose CT. The NCCN is the first professional organization to perform the comprehensive review and update their recommendations to promote lung cancer screening.
This update further validates the key concept that high risk patients benefit from screening. High risk patients for lung cancer diagnoses are those who are multiple pack year smokers for 25 of more years. For these individuals, low- dose CT screening reduces the number of lung cancer deaths by 20 percent.
While we don’t really know the full cost of a screening program – such as the costs of working up false positive CT findings, the benefit in lives saved seems to justify considering screening now.
Fortunately, the CT technique for screening is low dose and involves low radiation dosage.
RSNA (Radiological Society of North America) is the largest annual trade show in the world, with about 55,000 people in attendance for the 6 day event in Chicago, Illinois. The expo includes a large number of presentations and courses on science and modern radiology.
RSNA 2011’s two main themes were lower radiation dose in diagnostic radiology imaging (especially CT) and new technology. For lower dose, there was much material on tailoring a CT scan exactly to an individual patient – based on their body size, their cardiac output, their disease process, or the type of diagnostic challenge. Additionally, a lot about new iterative reconstructions in CT – both statistical and model based, was presented. Either method lowers dose a lot, but model based results in lowered radiation exposure by up to 80%.
New technology presentations and courses covered a range of topics including dual energy CT for better tissue characterization, and the combination of imaging modalities in one platform – like SPECT/CT, or PET/MR. These combined modalities may provide a better combination of disease identification plus precise localization.
In all, RSNA 2011 offered great insights and interesting presentations. Did you attend? Share your thoughts below!
A recent presentation at the 2011 International Society for Computer Topography (ISCT) meeting in San Francisco highlighted the effectiveness of using dual- energy CT for abdominal imaging. This CT- technique has become more promising for uncovering certain pathology that has otherwise been hidden by traditional diagnostic imaging procedures.
Dual- energy CT- by whatever technology – can be configured to employ less radiation than single energy CT. But for some specific applications, it produces more diagnostic and specific information. Dual- energy CT currently may be the best radiology technique for characterizing urinary tract stones to their chemical composition (which determines whether medical, shockwave, or laser therapy will be required), characterizing small renal masses, and characterizing liver masses into cyst versus tumor.
Additionally, dual- energy CT may apply to better detecting minimal liver tumors, lowering the amount of iodine needed for CT angiograms, and creating virtual non- contrast scans. The latter may reduce the overall CT radiation dose of a multi- phase study by 20 to 50 percent!
While dual- energy is still relatively new to the field, it is clear that it is a promising technique for CT dose reduction, while maintaining imaging quality. Further research and testing will be conclusive of the absolute benefits of dual- energy CT.
The RSNA 2011 conference marks the 97th Scientific Assembly and Annual Meeting. This event, the world’s premier medical meeting for radiologic professionals, is being held on November 27 through December 2 at the McCormick Place in Chicago. The annual conference includes unparalleled education and professional development, networking opportunities, and a cutting- edge technical exhibition.
I will be involved in a number of events, both as a presenter and an author. The presentations that I will be involved in include:
• Presenter- Hot Topics: Dual- Energy CT on Tuesday, November 29 from 7:15 am to 8:15 am.
• Presenter- Refresher: Mind Your Own Business! Required Business Skills for Your First Job on Thursday, December 1 from 4:30 pm- 6:00 pm.
• Author/ Participant- Gastrointestinal Series: Scientific Formal Presentation (Dual-Energy CT of Hypervascular Liver Lesions: Evaluation of Lesion Contrast-to-Noise with Different Monochromatic keV Reconstructed Images) on Monday, November 28 from 9:50 am to 10:00 am.
• Author/ Participant- ISP- Health Services, Policy, and Research- Scientific Formal Presentation (Patient Knowledge and Perceptions about Radiation from Diagnostic Imaging) on Monday, November 28 from 3:30 pm to 3:40 pm.
• Author/ Participant- Neuroradiology Series: Stroke Imaging- Scientific Formal Presentation (Changes in the Measured Size of Atherosclerotic Plaque Calcifications in Dual-Energy CT of ex Vivo Carotid Endarterectomy Specimens: The Affect of Different Monochromatic keV Image Reconstructions) on Wednesday, November 30 from 11:00 am to 11:10 am.
For more information about RSNA 2011 and the presentations that I’ll be involved in, please see the meeting program.
A recent article published in the American Journal of Roentgenology touched on the importance of taking a team wide approach to CT radiation dose reduction. While CT only account for about 15 percent of diagnostic imaging exams, it is responsible for contributing up to 70 percent of radiation dosage to the population, according to this study. Hence, the reason why it’s imperative to have the whole team on board when it comes to reducing CT scan radiation exposure in patients.
Ensuring that CT exams are appropriate is a critical component of overall dose reduction. At UW, we use a computerized Decision Support program, which acts at the point of Computerized Physician Order Entry (CPOE) to check appropriateness. Radiologists also double-check at the time of electronic protocoling.
At the time of the scan, the use of external body shields – including breast shielding – is important. Additionally, patient centering in the gantry is critical and can lower dose by as much as 40% compared to off-center exams. The routine use of iterative reconstruction technique – compared to the older FBP – can further substantially lower dose.
By having low- dose protocols and procedures set in place, we can be sure that we are providing our patients with the safest, most effective imaging procedures!
I was recently asked the question: “How low is low enough for CT?” With the risks of CT scans, the answer is: as low as you can go without significantly compromising diagnostic power.
Sometimes we do very noisy CT exams at extremely low doses, knowing that we may miss a 1 mm ureteral stone. However, we accept that possibility since such a small stone may not be clinically relevant.
Our routine abdominal/ pelvic exam is noisier than most of the CT exams we see referred in – but we deliberately chose to become accustomed to the higher noise levels (even when using iterative reconstruction) in order to minimize CT radiation dose. Thus, our doses are 40 percent lower than those on some of the CT scans we see being administered at many other places. There is no evidence we have compromised diagnostic power with our reduced dosage CT scans.
In today’s world, the 1-3 mSv cardiac CT is commonplace. In the near future, a CT of the abdomen and pelvis (40 cm of Z axis) using 0.6 mSv will soon be commonplace with the arrival of model based iterative reconstruction. With MBIR recently becoming available in the United States we will soon see dose reductions of up to 80 percent!
I came across an article from the Journal of the American College of Radiology on a number of recommendations for optimizing patient dose level in chest CT scans, the third most commonly performed CT exam in the country.
As the article points out, the lungs are an ideal organ for low dose radiation CT scans. Some of the recommendations offered include:
- Doctors should ensure that patients understand all instructions fully, including when to hold their breath and how much movement is permitted.
- Automated exposure control (AEC) techniques should be used as often as possible to assist with breathing in children and adults.
- Iterative reconstruction techniques reduce radiation dose exposure substantially and should be performed as often as possible.
- Centering patients in the gantry isocenter avoids excessive scan length dose. Additionally, CT scans should only be performed on the area of indication.
- Reading thicker sections ensures CT scan radiation risk reduction, while allowing fine details to be examined in nosier, thicker sections. This procedure should be utilized by imaging professionals.
- All CT scans should be done for a clinical and justifiable reason.
The tips and pointers in this article are all good tools for lowering patient radiation dose in chest CT. We have found that the use of iterative reconstruction is a big help – lowering dose by as much as 40%. Now that model based iterative reconstruction has recently become available in the USA (GE’s version is called VEO), we can look for dose reductions of more like 80%!
A recent study published in the Annals of Emergency Medicine on the rapid increase in CT scans being performed in Emergency Rooms (ER) paired with the decline in hospital admission rates between 1996 and 2007, got me thinking. During this time, the number of CT scans being performed increased by 330 percent, while the rate of those admitted following a CT scan decreased from 26 percent in 1996 to 12.1 percent in 2007. Does this mean that more patients are receiving unnecessary radiation exposure? Well… not necessarily.
The article points out a conflict about the use of CT in ER patients. Remember that practicing medicine in an ER is very different from a physician’s office. Patients are more acutely ill and ER congestion can be marked. Plus, time spent in the ER is very expensive.
In our study of patients presented to an ER with low to moderate risk chest pain, we found that a negative triple rule out CT resulted in shortening the stay by over 20 hours and cutting the cost of the ER encounter by 50%. Further, discharging a patient to home if their CT was negative was a safe practice.
Therefore, under the right circumstances, the use of CT in ER patients can be very effective. Our challenge is – through outcomes research – finding those right circumstances.
For more information on emergency medicine at UW, please see here.
A study published in a recent issue of the Journal of American College of Radiology asserts that CT -induced cancers are more likely to occur amongst rarely scanned young adults, as opposed to frequently scanned patients–the group that many assumed was at the highest risk for radiation induced cancer diagnoses.
It is still true that a definite relationship between cancer induction and less than 100 mSv of radiation has never been proven. This is assumed, for safety’s sake – based on proven relationships with much higher doses of radiation. Remember, a typical CT of the abdomen and pelvis in the modern world is about 6-10 mSv.
The other variable that has never been proven is the assumption that the risk from multiple scans which are widely spaced in time is additive. In fact, we know that the body has tremendous capacity to heal and repair any kind of damage – so any damage from a single event of low dose radiation may be fully repaired before a second event occurs. Hence the effect may not be at all additive.
So… results like those found in this article are not surprising.
Nothing, however, should lessen our vigilance about striving for as low a radiation dose as possible for all medical diagnostic imaging applications. In a world of unknowns (and possibly unknowable’s), that’s just common sense.
GE recently announced the introduction of a breakthrough low- dose imaging reconstruction technology in Canada. This CT image reconstruction technology, called Veo, is the first Model- based Iterative Reconstruction (MBIR) technique. The technology is a response to radiologists’ demand for a technique that maximizes CT image clarity and quality while optimizing the dosage level for patients’ safety.
MBIR is indeed a radical breakthrough in the drive toward lower dose CTs. While very computationally intensive, this technique allows marked reduction in patient dose from CT (by up to 80% or greater), yet also provides some improvement in spatial resolution without compromising contrast resolution. How could all that be possible – seemingly defying the laws of physics? The answer is in the much faster computational speeds of the modern computer chip.
The University of Washington will be part of the group assessing the degree to which MBIR, commercially known as Veo, outperforms more traditional CT reconstruction techniques.
A recent article on Time.com discusses situations where physicians may “bend the truth” in order to arrive at quicker results – in this case, the decision to perform an appendectomy.
CT scanning without oral contrast for possible appendicitis gives up several percentage points in accuracy. A radiologist may mistake a non-contrasted terminal ileum for an inflamed appendix. And the earliest sign of appendicitis is called the arrowhead sign, which is contrast in an edematous appendiceal orifice – cannot be detected without the contrast. Many surgeons take comfort from the presence of contrast in the appendix as evidence that portion of the appendix is not obstructed and inflamed.
Sure you can cut corners and save time. The ultimate time-saving corner to cut is to not do a CT and just decide based on physical exam plus lab results. The accuracy of CT without contrast is similar to that approach. But if we do CT in order to get more accurate diagnosis, we need to have the CT do its best job in terms of accuracy… which requires oral contrast.
In my opinion, the time saved by doing CT without oral contrast definitely does not justify the loss in accuracy. Pressure to practice this way comes from well intentioned folks who do not have to interpret CT exams themselves, and stand by the results.
Earlier this year, I wrote a blog entry about the news surrounding an important study involving CT and lung cancer screening. Now, the same study is making big headlines again as stronger (final) findings have been released. According to CNN, the study found that “low-dose CT screening reduces the number of lung cancer deaths in high risk smokers by 20 percent.”
Here’s another interesting fact coming out of the latest data: In high-risk populations, lung cancer CT screening can save a life for every 300 people screened. That’s more potential lives saved than mammography, colonography and prostate cancer screening COMBINED!
The only hitch: lung cancer CT screening is not covered by most insurance. However, many hospitals and imaging centers are offering this service at attractive rates for those who are willing to pay themselves.
The following is an interview I conducted with Dr. Lee Mitsumori, Assistant Professor of Radiology at the University of Washington.
Dr. Shuman: Please give us a brief overview of your work involving weight-based selection of CT parameters.
Dr. Mitsumori: We have been investigating the use of body-size-dependent CT scan parameters to optimize the radiation dose of each scan. Several imaging parameters can be modified at the time of the CT that can alter the amount of radiation of the scan (tube current, tube potential, scan range, scan phases, image reconstruction techniques). The challenge is to adjust each so that the final set of patient images are of diagnostic image quality and were obtained with the lowest possible radiation dose. The risk is that incorrect settings or too aggressive dose reduction can create a scan that is of poor image quality that does not allow a correct interpretation. Current work at University of Washington Medical Center involves studies comparing different CT image reconstruction techniques (adaptive iterative reconstruction, model based iterative reconstruction) that can significantly reduce CT image noise and how these can be best implemented in patient CT exams.
Dr. Shuman: Why is weight an important concern regarding CT? How does weight affect CT?
Dr. Mitsumori: A patient’s body size, as reflected by weight, affects two important feature of a CT scan. The first is the amount of photons needed to generate an interpretable CT image. A CT is a projection technique, where an x-ray source emits photons that then pass through the subject before being recorded by a detector on the other side of the patient. Larger patients need more photons with higher energy than smaller patients to create images that can be correctly interpreted. If the CT parameters are not correctly set and only a small number of photons are recorded by the detector, the images created are noisy. If an image is too noisy, the interpreting physician may not be able to see if a problem or disease process is present. Unfortunately, the more photons used the higher the radiation exposure of the CT exam. While large patients are at risk for having noisy images, small patients can have scans done with parameters selected for an average sized patient, in which case too many photons are used than what would be needed to create diagnostic images. Thus, the importance of matching the radiation dose (number and energy of photons emitted) with the patient’s body size to prevent non-interpretable studies in larger patients, and avoid excessive radiation dose in the smaller patient.
The second feature of a CT scan where patient size is important is in the amount of iodinated contrast needed for the scan. Iodinated CT contrast is injected intravenously during the scan and improves the depiction of the different organs and vascular structures in the body. With CT imaging, the use of contrast greatly improves the radiologist’s ability to differentiate diseased (tumors, infection, inflammation) from normal tissues. Similar to radiation dose, the amount of contrast needed to enhance the organs is dependent upon patient body size. Small patients will have smaller organs, less blood volume, and be shorter than larger patients. Thus the amount of CT contrast needed may not be the same for every patient.
Dr. Shuman: What are the risks involved when a hospital or imaging center does NOT take a patient’s weight into account?
Dr. Mitsumori: The risks for scanning with fixed CT parameters are that when compared to an average sized patient, the large patient may have scans with noisy CT images that could lead to interpretation errors, or a non-diagnostic scan in which the scan may need to be repeated or an alternative imaging test performed. For the smaller patient, the risk would be that more radiation is used than what is needed to generate adequate, diagnostic images.
Similar risks occur with CT contrast administration. If a fixed amount of contrast is used for every scan that is based on an “average” patient size, then large patients may not receive enough contrast to adequately enhance the internal organs rendering the scan potentially non-diagnostic, and the small patients are given more than the amount of contrast needed to obtain an adequate scan.
Dr. Shuman: When discussing CT exams with their doctors, are there questions a patient should ask regarding their weight? In other words, what would make an “informed patient” as it relates to weight and CT?
Dr. Mitsumori: An informed patient would want to ask if their CT scans will be performed with “patient tailored” or “patient specific” protocols that use the amount of radiation and iodinated contrast that best match the patient’s body size.
I am often asked what, exactly, iterative reconstruction is – and why it is so important. I thought it would be a good idea to discuss what I do and what my work means for the University of Washington Medical Center and our patients.
A brief overview of iterative reconstruction
Iterative reconstruction to us means potentially significant radiation dose reduction to our patients, but the look of the CT image itself needs some getting used to. When we first got the option on our scanners, we wanted to make sure that our radiologists would be comfortable with the images produced.
So, based on our protocols at the time, we reconstructed them with varying percentages of iterative reconstruction and noise indexes, and had our radiologists evaluate the images and decide what they found to be the most similar in noise and image quality to our standard at the time.
They used a double-blind method to evaluate the images, and based on what they decided, for noise index and iterative reconstruction percentage we were able to reduce radiation dose to our patients by 40-60 percent.
The evolution of iterative reconstruction at UW
We are constantly striving for improvement in image quality and dose reduction – both of which lead to better patient care. So we look again at our existing protocols and evaluate how we can combine certain series or opt for higher noise indexes in order to reduce dose. We also introduce different percentages of the iterative reconstruction and display these for our radiologists to further evaluate.
What UW is doing that others aren’t
Our radiologists are always willing to go out of their comfort zone in order to reduce dose. I say this again because of their willingness to take the time to look at images that traditionally would not be pleasing to their eyes, but may be more than adequate for answering the questions that the ordering physicians need.
And, again, a prime example of that is the different percentages of iterative reconstructions that they’ve seen and continue to look at, in order to properly evaluate the balance of dose vs. image quality – and always striving to improve both.
Why this work is important for patients
We always put patients first. To do this, we need to make sure that we give the right amount of radiation dose. With the modern machines we have, it is far too easy to give too much dose to produce the prettiest of images, but easy is not safe. To use these modern machines properly and responsibly takes a lot of extra work to accurately and safely fine tune each protocol for each patient’s needs. Our patients deserve all of that extra effort and more.
What does adaptive iterative reconstruction do? How is it used?
These are questions addressed in an article of mine featured on the Image Wisely website. As mentioned before on this blog, Image Wisely is an excellent and very useful resource – for both health care providers and patients – that provides information on low dose protocols, radiation risk, and safety in medical imaging.
To read the full article, click here.
The American College of Radiology, in an effort to address questions and concerns about radiation risk, has created several public service announcements that inform viewers where they can obtain more information regarding radiation in medical imaging. These PSAs have been released for nationwide broadcast.
The adult-focused version of the announcement directs viewers to the Image Wisely site, while the pediatric version directs viewers to the Image Gently site. Each site individually serves as the primary resource for additional information on imaging and radiation safety.
The PSAs can be found here.
A New York Times op-ed about nuclear radiation exposure, called “Unsafe at Any Dose,” got me thinking about CT scan radiation exposure – and the ongoing debate regarding CT scan risks.
Many activities and endeavors in human life have associated risk. Driving a car is risky; people die. And the more miles you drive, the greater the risk. But that does not mean we don’t use cars. Rather, we minimize risk by driving carefully, using seatbelts, etc. And we go ahead and drive in order to capture the benefits.
So it is with medical radiation… and nuclear energy. But an important note: even with Dr. Caldicott’s pessimistic predictions and numbers, if you look at human deaths associated with kilowatt hours of electrical generation, coal powered electricity is the worst. Oil is next, and nuclear is at the vary bottom of the list (i.e., it has historically caused the fewest deaths).
Makes one stop and think, doesn’t it?
Here on this blog I often talk about the importance of patient education and awareness, as it relates to CT scans, radiation dose and cancer risks. Informed patients are smart patients! To that end, I wanted to share with you an interesting resource I recently came across: a “radiation risk calculator” sponsored by the American Society of Radiologic Technologists.
According to the site, the purpose of this (free) tool is to “calculate your dose and estimate cancer risk from studies including CT scans, x-rays, nuclear scans and interventional procedures.” I think this is good for patients, if combined with counseling about the meaning of the numbers.
I always say: the more info, the better – as long as it is understood appropriately. Remember too, that a 1 in 2000 risk of causing cancer means a 1999 in 2000 risk of not causing cancer…
Recently, an episode of Dr. Oz that linked the increase in thyroid cancer to imaging and biopsy procedures prompted an increase in requests for thyroid shields from women undergoing mammograms. The cancer risk scare appears to be caused by a chain e-mail that was created by a viewer after the episode aired. The public outcry has reached the point that the American College of Radiology and the Society of Breast Imaging have issued a joint statement to try to overcome fears of high radiation risk from mammography.
Here in our own offices, we have women showing up for mammograms bringing their own thyroid shields. This is silly – the amount of scatter radiation is so small as to be hardly measurable with very sensitive instruments.
If you take a thyroid shield to a mammogram, to be logically consistent, you should be wearing it all the time – on any airplane flight, when sunbathing… the list goes on!
Recent findings from blog contributor Dr. Kalpana Kanal and her team of University of Washington researchers have been published in the April issue of the Journal of the American College of Radiology!
The purpose of the study was to examine the variation in pediatric trauma head CT imaging protocols in Washington State – including the use (or not) of low radiation dose CT. Based on their findings, the team is now working on a campaign to adopt CT dose reduction protocols throughout the state. For more information on the study, click here.
Great work by Kalpana and her team!
Unfortunately, ct scan radiation overexposure continues to be a problem in hospitals and imaging facilities across the country. However, the question of regulation of dose from ct scanners is a complex issue. Many say that the best pathway to regulation is through the existing American College of Radiology mechanisms – such as certification of CT sites and subspecialty certification of both radiologists and CT technologists. This may expand to include requirements for regular monitoring of dose from typical exams and reporting the results of such monitoring to a central ACR registry.
Others advocate a role for the FDA, though that government agency may turn to a group of experts, such as the ACR or the Society of Computed Body Tomography. A national registry of individual patients which records dose from each CT exam for each patient, and cumulative dose for each patient, would also be a best practice – Europe does this now in the EU.
Finally, we need many and repeated courses, texts, electronic educational media, and monographs focused on the topic of how to consistently achieve CT scans at much lower dose than a few years ago. This education should be widely available and ongoing.
Our recent UW Symposium on Low Dose CT was a repeat from six months ago, and was equally well attended.
Check out this KING 5 news story where I discuss the recent discovery of trace radiation in milk being sold in Washington, due to the Japanese nuclear power plant leaks. As I mention in the interview, there’s no cause for concern, given the amount of radiation being detected. It’s a tiny fraction of the dose you’d be exposed to during a CT scan, for example.
Watch (and read) the interview here.
A new study published in the March issue of the Journal of the American College of Radiology shows that the use of virtual colonoscopies at U.S. hospitals is increasing – even though the procedure is not covered by Medicare.
A neat feat of virtual colonoscopy is how the radiation dose associated with the exam has dropped considerably since it was introduced. Newer reconstruction techniques on newer CT scanners have made this possible.
While it is still true that Medicare will not pay for any type of screening (except mammography), some commercial insurance companies have realized the value of screening for colon cancer, particularly in high-risk patients. Screen CT colonography does well when compared to other tests for detecting colon tumors and polyps. And patient acceptance is higher because it is quick and less uncomfortable.
I am extremely pleased to report that our second, back-by-popular demand Low Dose CT Symposium went very well! It was attended by 140 healthcare providers, which was an impressive turnout. Talks were excellent and very engrossing. There was a great discussion panel for the final half-hour (it actually went on for another half-hour after the meeting since there was so much discussion coming out of the questions!). An audience survey score was 5.4 out of a possible 6 for quality and impact on practice.
Were you there? What did you think?
…for dead people.
Check out this interesting story, “Radiology Helps Unwrap Mummy Mystery,” about a radiology lab helping out a university museum with some mummy research. They were hoping that, through the use of CT scans, they’d learn some valuable information about the mummy and the person he once was.
What caught my eye was this quote: “Radiation protection is very important in living humans…but this concern was completely inapplicable to this situation. So we were able to do two things: we were able to use a much higher radiation dose and also use much thinner slices than we would typically use on living patients to examine them.”
Amusing, isn’t it? Dead people are willing to pay the price for images that look too good: high radiation.
One of the most common complaints of patients in the ER is abdominal pain, and as a recent article at TIME.com details, diagnosis is rarely straightforward. It is important to understand that the ER is different from other places where healthcare is provided. ER physicians see a broad spectrum of disease – from the insignificant to the life-threatening. There are great time constraints in the ER, as well, and follow-up care is hard to arrange (and may be unreliable) so there is pressure for a definitive diagnosis in a single encounter.
Physicians considering the CT scan to assist with diagnosis for abdominal pain or other illness and injuries should consider three questions:
1. Is CT the right test to do for this patient?
Many ER physicians are good at a answering this question, but it is also helpful to remember that the best expert on appropriate use is one phone call away: the radiologist. Having the patient’s EMR handy is important, too, in reporting how many CT scans this patient may have had historically, since this is a data-point in choosing whether or not to do CT. A national registry of individual patient cumulative radiation dose is coming to the U.S., similar to the one that now exists in the EEU, but it is not here yet.
2. If CT is the right test, what kind of CT?
With contrast or without? Oral contrast or not? Positive oral contrast or negative? One pass or three? Arterial or portal venous phase? Abdomen only or abdomen plus pelvis? Again, the radiologist is a valuable consultant for getting the most information about the patient’s condition at the least radiation cost.
3. How can the CT scan be done with the lowest possible radiation dose?
Finally, once the kind of CT exam is decided, how can it be done with the lowest possible radiation dose without compromising the diagnostic value of the scan. A well-informed radiologist can reduce the radiation dose per scan by up to 60 percent. For example, CT of the urinary tract with contrast now can be achieved in a single pass. Careful attention to CT imaging parameters can radically lower dose (low kVp, modulated mA, etc.). Limiting the length of the scan on the patient and careful centering of the patient by the tech can greatly reduce dose. In addition, newer scanners combine better detectors with more complex reconstruction algorithms to substantially lower dose and CT scan radiation risks.
Just wanted to let you know about a couple of upcoming events…
First, I’ll be speaking at Overlake Hospital in Bellevue, WA, at the quarterly Meeting of the Association of Hospital Radiology Administrators on Low Dose CT. This is taking place on February 23, 2011, at 5:30 p.m.
Coming up in early March, I will be Visiting Professor at the University of California, San Diego. On Tuesday, March 1st, I’ll be attending Grand Rounds at 7:30 a.m., and speaking at the San Diego Radiology Society at 7:00 p.m.
The Low Dose CT Symposium is a repeat session of the October 10, 2010 symposium which drew close to 150 people and was greatly received! It will be an excellent opportunity to gain understanding of the current thinking about how to lower dose in CT scanning without compromising the diagnostic power of CT. Radiologists, physicists, and senior technologists are combining their knowledge and experience in multiple 20-minute talks about Low Dose CT technique, covering all aspects of protocols, technique, and ordering appropriateness for use of CT.
The half-day symposium is taking place March 12, 2011, in Seattle at the University of Washington Health Sciences’ Turner Auditorium, D-209. The symposium is available for a maximum of 3.5 AMA PRA Category 1 Credits™. Registration is required to attend.
For more information on the event — and to register — please visit www.lowdosecteducation.com.
Here’s a guick look at the agenda:
|8:30am||Welcome||William Shuman, MD, FACR|
|8:40am||Why the Unexamined CT Can Be Very High Dose||Kalpana Kanal, PhD|
|9:00am||Low Dose CT Technique||William Shuman, MD, FACR|
|9:20am||Low Dose CT in the Abdomen: Practical Applications||Carlos Cuevas, MD|
|9:40am||Low Dose Techniques for Vascular CT||Lee Mitusmori, MD|
|10:20am||Low Dose CT: The Technologist’s Perspective||Mario Ramos RT,CT|
|10:40am||Low Dose Cardiac CT — Coronary Arteries, Whole Chest, and Beyond||William Shuman, MD, FACR|
|11:00am||Educating Patients about Radiation||Janet Busey, MS|
|11:20am||Low Dose CT in the Acute Care Setting||Martin Gunn, MD|
|11:40am||The Future of Low Dose CT||Paul Kinahan, MD|
|12:00-12:30pm||Questions and Panel Discussion|
Hope to see you there!
A recent article in Health Imaging discusses a study that caught my eye. According to the study, the article noted, 80 to 90 percent of radiologists remain “invisible to their patients and approximately half of the public is unaware of whether radiologists are physicians or technicians.” In effect, the “commoditization of radiology is becoming a pressing concern to many practitioners.”
The authors of this study provide a good solution: “By offering an even higher level of personalized service through direct communication, radiologists can dispel this viewpoint by showing patients that they customize imaging examinations to fit each patient’s individual healthcare needs.”
I find this relates to my own experiences as a radiologist and, in a way, to the low dose movement. One way to lower the dose of CT is to not do inappropriate CT scans. How do you decide what is inappropriate?
This is where the radiologist (a physician) as a knowledgeable advisor (who consults with other physicians about imaging) comes in.
Face time with patients can help them understand this role. It can also help them understand that lower dose in their appropriate CT exams is possible without compromising the diagnostic power of the exam – again, achieved through a knowledgeable radiologist designing the CT exam and monitoring the conduct of executing the exam.
In the last few months I’ve read several stories concerning research about CT screenings for lung cancer.
In mid-November, there was a story making the rounds among the major news outlets about a study that found that CT lung scans can reduce the risk of lung cancer death among former and current heavy smokers. During the excitement of this study, a New York Times piece was published that expressed concern that the study’s findings could easily be taken out of context – and perhaps incite unnecessary fear, as well as drive demand for unnecessary scans.
I’d like to point out the importance of this study: it showed a 20 percent reduction in mortality in patients at very high-risk who were screened with low dose CT compared to patients who were not. Several things to keep in mind about this study – first, it was a study of patients with 30 or more pack-years of smoking history. Second, the technique was a quick and a low dose CT. And third, the costs of false positive findings and their workup have not yet been analyzed.
Now, another study is gaining traction that provides even more support for the findings of the November study. While this data suggests that screening can lower lung cancer mortality substantially in high-risk individuals, what we don’t yet know is the cost of a QUALY – a quality adjusted life-year. Calculating that cost involves knowing how much society had to expend paying for CT exams and the costs of false-positive results in order to capture a saved life-year in an at-risk person. Generally, if you can save a QUALY for $50,000 or less, it’s worth doing. If more, it’s a debate.
Just some things I’ve been thinking about as more and more news agencies report on these findings. I’m interested in learning what you think – what’s your opinion on these studies? Was the New York Times piece correct in its cautionary tone? Or could these findings, in fact, be as revolutionary as some reporters (and researchers) want us to believe?
A recent study I came across found that patients in emergency departments have very high confidence in CT scans and technology. Furthermore, it seems as if patients get increasingly more confident that they’ll get a proper diagnosis the more testing they have done. But compounding this is another finding of the study: most patients’ understanding of radiation exposure is poor.
The key to this discussion is the concept of appropriateness. What that means is the balance between cost, risk, and the chance that a test may provide valuable information, which impacts on therapy, outcome of the disease process, or peace of mind (which has value, too).
As this study points out, patients have confidence in CT, but that confidence does not translate directly to appropriateness. Risk of CT radiation is hotly debated, but that too does not equate with appropriateness by itself. And cost effectiveness is just one component of the stew that is appropriateness.
So, given all those limitations, how do we get there? Answer: use the radiologist – equipped with powerful support tools – as a consultant to find the balance that optimizes appropriateness. The radiologist is an epicenter of knowledge about radiation risk, cost effectiveness, and the potential positive impact of a CT. Add to that support from a decision support program – which is a compilation of all knowledge in these areas – and you have the best path to appropriateness in this complex world of high-tech imaging.
An article that was published after RSNA talks about a study that found that CT scan radiation risk in patients may be overblown. However, at the close of the article, it says that longer-term, more in-depth study is needed. Until then, physicians and patients still need to weigh the risks and benefits of CT.
For patients to both be informed and to understand (comprehend) risk related to radiation is very challenging. This is because there are few comparables in normal daily life which can clearly quantify extremely small risks. The one I like the most is: 10 mSv give you a risk of dying from an induced cancer of about 1 in 4000. Driving a car in the USA for 80,000 miles over 3 years also gives you a risk of about 1 in 4000 of dying in a car accident.
Now, both a CT scan with 10 mSv and 80,000 miles of use of a car bring certain benefits. But they carry a risk of dying of 1 in 4000. What do you think of that risk/benefit ratio? Would that ratio make you stop driving a car?
I recently came across this video from RSNA. About halfway in, they ask the question, “What is the biggest advancement in CT technology this year?”
I would agree with Dr. Siegel that iterative reconstruction has stimulated thinking and conversation among radiologists about how to substantially lower CT dose without compromising the benefits of CT. Based on our 18 months of experience, we know the reduction is at least 40 percent with the current version of iterative reconstruction. And we suspect much greater reductions are coming. Some of the issues centers around radiologists’ “preferences” for how a CT images looks. But preferences can change, even dramatically, when driven by the hope of much lower patient dose.
What do you think – what do you view as the biggest advancement in CT?
One of the most exciting – and talked about – sessions at RSNA was called “Radiation Dose: Can It Be Too Low?” The expert panel had a healthy debate on radiation dose and risk, and finally reached an agreement that CT scans should be limited to “justified and optimized studies.” (HealthImaging.com has a good recap of the panel’s discussion.)
The debate about risk can go on, but when practicing medicine (radiology) with real patients, the obligation is to both minimize risk AND maximize benefit.
So the challenge for radiologists is to lower dose as much as possible without compromising the amazing diagnostic power of CT. How to accomplish this is both science and art. But we have discovered at UW that with a combination of low dose technique and low dose CT technology, you can take out up to 40 percent of the radiation dose to the patient (compared to 3 years ago) without having any negative impact on diagnosis. So that number certainly is achievable at most sites.
Could we go even further in dose reduction?
A new method of extracting and archiving patient CT dose information has been developed, according to a recent article in Science Daily. Called RADIANCE, this new system should help with compliance with the American College of Radiology’s reporting guidelines and build greater awareness of radiation dose to patients.
Tessa S. Cook, M.D., lead author of the study that lead to RADIANCE, says that extracted radiation dose information “can be used to perform a variety of analyses aimed at quality assurance and patient safety. The automated extraction ‘pipeline’ for radiation dose information allows us to be more cognizant of radiation dose to our patients, thus resulting in improved patient care and management.”
It is clear that we are headed toward the recording of radiation dose from each CT scan in the patient’s medical record. Initially, this will be in the PACS archive, then in the radiology information system (RIS) on the way to being in each radiology CT report. Eventually, the dose will reside in each patient’s electronic medical record (EMR) and a cumulative record as well – just as they do in Europe today in the EEU.
RADIANCE is a big step in that direction.
In the days that followed last month’s Low Dose CT Symposium, I had time to reflect on how wonderful it was that the event drew an unprecedented number of attendees. The interest in the symposium was evident by how far some attendees traveled to get there. I was also struck by the segments of the industry that were represented in the audience: technologists, radiologists, technicians and administrators were all there. It made me think about each segment’s relationship to one another, and their ability to impact change in the industry.
When driving toward much lower radiation dose in CT, it’s good to remember that a team effort is needed. Technologists must be educated on all the tricks and skills needed and must fully understand why dose reduction is important. They can help radiologists be more conscious of dose exactly when radiologists are urging technologists to pay close attention. Both techs and radiologists can use their knowledge to help educate administrators about the importance of investing in low dose CT. Everyone can help educate referring clinicians about thinking of dose when they order, both for an individual study and cumulative dose (over time) in individual patients. And it is the whole chain of providers who monitor appropriateness of studies at each and every level.
Lots of articles are published on a regular basis that talk about public awareness (or lack thereof) of CT scan risks and benefits. This one’s a recent example. But here’s the thing, which I’ve discovered through personal experience: educating patients about radiation risk is very challenging. This is because extremely low rates of risk are hard to comprehend. It can be talked about in terms of background natural radiation, or risk of driving a car, for example. While it is important that patients be informed, it is also important that they not be scared away from a test that stands a good chance of helping them – a lot. This is a fine balance.
Practicing medicine in an emergency room environment is different from in a clinic or a hospital. The diseases are different as is the acuity. What may not be appropriate in a family medicine clinic population may be appropriate in an acutely ill ER patient.
This is why specialists in radiology and emergency medicine are continually reviewing appropriateness criteria, like those published by the American College of Radiology.
A new study published in the November issue of the American Journal of Roentgenology concluded that patients from the emergency department are more concerned about having their condition diagnosed with CT than about the risk of future cancer from radiation exposure.
Although the patients in this study did not estimate the risk of development of cancer as high, the majority of patients wanted someone to discuss the risk and benefits of testing them. This is not as simple as it sounds. How do we best educate patients about radiation? Who is responsible for educating patients about risks and benefits of radiation exposure from CT – the ordering provider, the radiologist, or the CT technologist?
Right now it seems that nobody is doing such education likely due to time constraints and the fact that it is a difficult topic to discuss. There is no standardized way to discuss radiation with patients and research shows that many physicians don’t fully understand radiation, radiation doses from common tests or possible risks from exposure to radiation from medical imaging. This is a topic that is not going away. We know what our patients want and need, it’s up to us as their healthcare providers to deliver.
Aunt Minnie recently reported on a study that found that when emergency room personnel are knowledgeable about protocols for transferring and accepting DICOM CDs – which contain images of emergency CT scans of injured children – there is a decrease in the number of repeat (unnecessary) exams performed.
However, the authors of the study said that problems arise when CDs aren’t transferred to the appropriate personnel, leading to unnecessary exams (and unnecessary radiation exposure) even when a CD exists, according to the article.
Another approach – one which we follow – is to set up pre-existing VPN communication networks so studies can be directly downloaded (quickly), without the need for CDs. These often arrive before the transfer of the patient. They are set up with the sites that refer more than 5 patients per year. Here we have about 200 such connections to other healthcare facilities, which is great for all medical records as well as the images from radiology.
To recognize National Radiologic Technology Week, I asked respected CT technologist (and our CT supervisor) Mario Ramos to share his perspective on the benefits of low radiation dose CT. — Dr. Shuman
Proper dose reduction is not just about having the right equipment. It is essential that everyone is involved, and that they all work as a cohesive team in the name of patient safety.
Management supports us by making sure that the right machines, maintenance contracts and people are in place. Our radiologists ultimately determine the level of noise we allow in images, and that dictates the steps we take to reduce dose. As technologists, we have to have the right workflow in place to make sure that all those steps for dose reduction are done, such as adjusting kV, ma, noise index, and proper shielding. Our support staff assists with the busy work that can take away from the focus on the scan at hand, and the physics teams keep our QA/QC protocols in check. We are very fortunate here at the University of Washington to have all these things in place and know that as equipment and scanning techniques continue to evolve, we are able to ensure the highest level of image quality while maintaining proper dose reduction practices.
I’ve got two events coming up I’d like to share…
The first, on November 4, is the Grand Rounds conference at Overlake Hospital. The conference will focus on radiation exposure and its potential risks with regard to patients receiving multiple imaging studies/multiple radiation doses. Should be interesting!
The second, on November 6, is the Washington State Radiological Society (WSRS) annual meeting. It’s at the World Trade Center in Seattle, and it’s scheduled for 4:00 p.m. Click here for more information about this meeting. If you’d like to attend, you can find the registration form available for download here.
November’s off to a busy start!
A recent study found that the use of CT scanners and other advanced imaging machines in U.S. hospital emergency departments “tripled between 1998 and 2007, resulting in higher costs and longer emergency room stays,” according to an article by blogger Julie Steenhuysen.
Lead researcher Dr. Frederick Korley of Johns Hopkins Medicine in Baltimore said his team noticed “a really significant increase [in usage] without a corresponding increase in the diagnosis of life-threatening illness.” He said this suggest that there is a “potential amount of overuse or use that is not directly yielding any meaningful clinical results.”
Actually, the use of all CT and MR from any source more than doubled during that time period.
Emergency rooms are under great pressure to diagnose or rule out serious conditions quickly, since every ER in the country is swamped with patients – many of whom cannot get to other forms of care. What is inappropriate in some settings may be appropriate in the ER setting.
In our study of patients with low-risk chest pain who had a cardiac CT early in their ER visit, patients were discharged 20 hours faster and with a 40 percent cost reduction compared to similar patients who had a workup without cardiac CT.
So it really depends on the indication.
Just a quick note: I’ll be giving my lecture on Low Dose CT this Thursday, October 21, at 6 p.m. at the Claremont Resort in Berkeley, CA.
Registration is through Alexandra.LaMarsh@ge.com.
Hope to see you there!
A new piece of legislation was announced recently that radiologists all over the country are talking about: California Governor Arnold Schwarzenegger has signed a medical radiation bill into law. It’s the first state law in the United States aimed at “protecting patients from excessive radiation exposure received during CT scans and radiation therapy procedures,” as reported by Aunt Minnie.
According to the same article, the bill “requires that radiation dose be recorded on the scanned image and in a patient’s health records, and that radiation overdoses be reported to patients, treating physicians, and the state Department of Public Health (DPH).”
Both the goals of this law are very commendable and worthwhile. Putting the dose of each exam into the medical record is done in Europe now and should begin in the U.S. This will require some commitment from radiation device manufacturers and from the DICOM standard, but is quite doable.
And disclosing errors, of any type in any part of healthcare, is just part of good practice.
The October issue of the American Journal of Roentgenology has just been released, and it features a recent study I conducted with blog contributor Janet Busey and colleagues Kelley Branch, Lee Mitsumori, Jared Strote, Douglas Green and James Caldwell.
The study, “Negative ECG-Gated Cardiac CT in Patients with Low-to-Moderate Risk Chest Pain in the Emergency Department: 1-Year Follow-Up,” shows that for patients with low-to-moderate risk chest pain evaluated in the emergency department, adverse cardiac events may be rare during the year after a negative cardiac CTA scan.
William R. Hendee, Medical College of Wisconsin, makes some very valid points in a recent article about overuse of CT scans and the harmful effects unnecessary exams have on both patients and the healthcare industry. Specifically, he says that radiologists can “play a big role in educating ordering physicians about what scans are appropriate and when.”
A big part of the training and experience-based learning of radiologists is what imaging tests are appropriate for specific healthcare problems and what imaging tests are inappropriate. Inappropriate means the imaging test has little chance of adding significant value to the diagnosis and therapy of the patient, especially relative to its cost.
The American College of Radiology (ACR) has spent more than a decade developing imaging appropriateness guidelines for hundreds of clinical problems and indications. These ACR appropriateness guidelines are based on the best available scientific evidence and were written by panels of best sub-specialized experts. The guidelines each get revised every three to five years as new evidence becomes available. There is no better source available for appropriateness of diagnostic imaging.
The decision support computer programs mentioned in the article start with the ACR appropriateness guidelines and create a quick way for referring physicians to know if any imaging test they order is appropriate. At the point of computerized imaging exam order entry into an electronic system, the decision support examines the entered indications for an imaging exam and then either agrees with doing the exam, or cautions that the exam may be only marginally indicated – or states that by generally accepted criteria the requested exam is unindicated. There is education involved, as the evidence-based reasons an exam is unindicated are provided to the ordering physician, along with suggestions for a better approach to the patient’s problem (often involving some other type of imaging). These decision support programs are now running in several healthcare enterprises, and they hold good hope for decreasing inappropriate complex imaging exam utilization without blocking access to appropriate tests.
The Low Dose CT Symposium will be an excellent opportunity to gain understanding of the current thinking about how to lower dose in CT scanning without compromising the diagnostic power of CT. Radiologists, physicists, and senior technologists are combining their knowledge and experience in multiple 20-minute talks about Low Dose CT technique, covering all aspects of protocols, technique, and ordering appropriateness for use of CT.
The half-day symposium is taking place October 2, 2010, in Seattle at the University of Washington Health Sciences’ Turner Auditorium, D-209. Registration is required to attend. Attendance is free, but a $25/50 charge applies to those attendees requesting CME credit.
Note for attendees: We’ve already been approved for 3.5 AMA CME Category 1 credits for the activity; ASRT credits pending.
Here’s a guick look at the agenda:
|8:30am||Welcome||William Shuman, MD, FACR|
|8:40am||Why the Unexamined CT Can Be Very High Dose||Kalpana Kanal, PhD|
|9:00am||Low Dose CT Technique||William Shuman, MD, FACR|
|9:20am||Low Dose CT in the Abdomen: Practical Applications||Carlos Cuevas, MD|
|9:40am||Low Dose Techniques for Vascular CT||Lee Mitusmori, MD|
|10:20am||Low Dose CT: The Technologist’s Perspective||Mario Ramos RT,CT|
|10:40am||Low Dose Cardiac CT — Coronary Arteries, Whole Chest, and Beyond||Kelley Branch, MD|
|11:00am||Educating Patients about Radiation||Janet Busey, MS|
|11:20am||Low Dose CT in the Acute Care Setting||Martin Gunn, MD|
|11:40am||The Future of Low Dose CT||Paul Kinahan, MD|
|12:00-12:30pm||Questions and Panel Discussion|
Hope to see you there!
Last year a New York Times investigation uncovered more than 200 radiation overdose cases at Cedars-Sinai Medical Center. According to a New York Times follow-up published on July 31 this year, 200 additional cases were revealed at other hospitals leading to more than 400 cases nationwide. The radiation overdose delivered to patients in these overdose cases was between 4 to 13 times higher than a typical dose for the performed scans. These overdoses led patients to experience hair loss, headaches, confusion, and may increase their long-term risk of cancer and possible eye and brain damage. The patients had received CT brain perfusion exams, which help to identify strokes through a number of blood flow images.
Why did these overdoses happen? This could be due to equipment malfunction, the need for “prettier” clinical images (requiring high radiation dose), or a serious lack of operator knowledge in setting up the CT imaging protocols for this type of exam. CT brain perfusion is a high-dose exam but can be performed safely if the technologists, physicists and radiologists work diligently together to ensure that the CT imaging protocols are set up optimally to follow the As Low As Reasonably Achievable (ALARA) principle. The dose delivered by this exam should also be monitored on a regular basis to ensure it remains at minimal levels and no equipment malfunction or dose creep has occurred. Physicians should also be aware of the potential side effects, as discussed above, which can be triggered by such high-dose exams.
Following 2009’s overdose discoveries, the FDA launched a collaborative Initiative to Reduce Unnecessary Radiation Exposure from Medical Imaging, to promote the safe use of medical imaging devices, support informed clinical decision making, increase patient awareness, and optimize patient exposure to radiation.
At the recent American Association of Physicists in Medicine (AAPM) annual meeting, the patient safety symposium focused on these overdose cases and the AAPM CT dose summit’s recent efforts to ensure CT scan parameter optimization and patient safety. The AAPM also produces reports on quality and safety in medical imaging and radiotherapy, along with letter-writing and policy campaigns targeted at the government and public.
Researchers at Mayo Clinic are also investigating the use of new image-processing algorithms to reduce the dose for CT perfusion exams up to 95 percent and maintain the same image quality as a high-dose perfusion exam.
If appropriate steps are taken to ensure patient safety and dose optimization, the benefits from a CT brain perfusion scan far outweigh the risks associated with it.
A recent editorial in the Journal of the American Medical Association took the position that the best course of action to address the issues of CT overutilization, quality control and training would be government regulation, according to an article on HealthImaging.
In the original editorial, authors David J. Brenner, PhD and Hedvig Hricak, MD reported that “the radiation dose in America has doubled over the past 30 years, and medical imaging contributes half of the dose to the U.S. population,” as stated in HealthImaging. They argue that only through national legislation will we be able to ensure lower CT radiation dose and an improvement in overall safety to patients undergoing CT exams.
Actually, there are very good resources available now for deciding appropriateness and supporting referring physicians, such as the American College of Radiology’s (ACR) appropriateness criteria or commercially available, evidenced-based decision support programs which are built into electronic order entry systems.
Rather than have the FDA develop a new agency, perhaps wider and better application of these existing resources and regulation through societies of experts (like the ACR and the Radiological Society of North America) might be impactful.
Despite the attention being given to the cumulative CT scan radiation effect and the buzz surrounding risks of repeat CT scans, one leading expert is disputing the theory.
As reported in Diagnostic Imaging, Richard Morin, Ph.D, chair of the American College of Radiology’s safety committee says, “There is no radiation biology to demonstrate CTs are additive in any way.”
Morin uses a driving analogy that relates probability of an accident to the number of miles logged by a driver, but notes that there is not a certain mile threshold, like 200 miles, that would trigger an accident.
I like the driving analogy and used it in my recent post Measuring Risk: Driving vs. CT. Driving is something that most of us can relate to, and therefore the numbers are more meaningful, so I’ve tried to quantify it even further.
Here’s how I like to look at the risk: The risk of dying from a cancer induced from a CT of the abdomen and pelvis in a middle aged male is similar to the risk of dying in a car accident if you drive 36,000 miles – both are about one in 2000.
The debates over cumulative dose theory will continue, and so I feel it’s important to explain the risks in ways people can understand – so that they don’t turn down any life-saving exams out of fear or misunderstandings.
While Dr. Morin explains that there is no way to figure out whether a person developed cancer due to radiation, a carcinogen or chance, he does say “it’s important that the right test is ordered at the right time.” I’ll add that it’s always a good idea to look at lowering the CT dose, too.
And while the effect of cumulative dose from multiple exams is unproven, we really must take the most conservative position when it comes to public health and assume the effect is cumulative.
Findings of a recent population-based study featured in the Journal of American College of Cardiology (JAAC) suggest cardiac imaging may be putting younger adults at risk due to radiation exposure.
“The study demonstrated that there are sizable rates of radiation exposure for patients 35-54 years, many of whom will likely live long enough for such long-term complications (as malignancy) to potentially develop,” wrote Jersey Chen, MD.
While the results may make cardiologists give further thought to the tests they recommend and alternatives they can use, others point out that the benefits of the test must be weighed against the risks of radiation exposure.
It is very unusual for a patient in this age range to get a cardiac CT scan. But if they do need one, we can now scan them using less than 2 mSv of radiation (compared to 10-25 mSv in 2005).
That means the risk of dying from a cancer induced by the CT scan (1 in 4,000) is about the same as the risk of dying in a car accident if they were to drive 70,000 miles (about 5 years of driving for the average American) which is also about 1 in 4,000.
Part of doing research at an academic institution requires consenting patients to participate in research studies involving radiation exposure. I’m always amazed at the number of patients that have no idea that their clinically ordered procedure involves radiation, because nobody took the time to explain this. Patients read the papers, they watch the news and they are fully aware of the ongoing media frenzy surrounding radiation in medicine. Patients often ask me, “Is it safe?” While the risk/benefit debate about ionizing radiation exposure continues to be a hot topic in the medical community, we must not forget to keep our patients in the loop.
Educating patients that radiation often is necessary in medicine can be extremely challenging – but it is more critical now than it has ever been. Talking to a patient about radiation exposure is much different than talking to your radiology colleague, especially when the true incremental risk to patients from medical radiation is still under much debate. There needs to be a coordinated effort at each institution to make sure that patients are receiving correct and accurate information about radiation. The imaging community needs to work together to devise websites and reading materials that educate the public about radiation exposure and risks versus benefits of imaging with radiation. Everyone involved in patient care must understand radiation, radiation risks, alternatives to scanning and what techniques are used to keep dose as low as possible.
Resources on explaining radiation to patients:
2. “How to Explain Radiation Risk” from the Washington State Department of Health
3. Wanzhen Zeng’s “Communicating Radiation Exposure: A Simple Approach”
CT radiation dose has recently been in the limelight, not only in the news media but also for patients undergoing CT exams. Estimating CT dose is complex and further challenged by the different types of CT scanners available in the market today. In a recent study, investigators collected CT radiation dose measurement data from all the multi-detector CT (MDCT) scanners used in the National Lung Screening Trial. Radiation dose in CT is defined as CT Dose Index (CTDI). CTDI represents the average absorbed dose, along the length of the patient’s body from a series of contiguous scans. Normalized CTDI can be used to determine the efficiency of the CT scanner, and finally the dose imparted to patients. Normalized CTDI represents the dose per mAs (tube current x rotation time) where the mAs determines the number of x-ray photons utilized per rotation of the CT scanner.
The results of this study imply that one needs to be aware of the differences in normalized CTDI – not only between manufacturers, but also between models of CT scanners from the same manufacturer (Table 4 of this study).
This study showed that the average normalized CTDI varied greatly (by a factor of 2) across all scanners from different manufacturers. The dose efficiency of the CT scanners improves as the scanners get more complex, with the number of detectors along the length of the patient increasing from four or eight to sixteen and beyond (e.g.: 4- 8- or 16- slice CT scanner). This has an impact on image quality and patient dose because the more efficient the CT scanner, the less the dose to the patient to acquire the desired image quality.
The dose data in this study was collected for 96 MDCT scanners across 33 participating institutions. While the study did not focus on image quality and patient dose, it did examine scanner-specific radiation dose data across all institutions.
A recent article addressing the ongoing debate over the safe use of medical imaging features the opinions of two industry experts on how we should be working to lower radiation doses from CT scans and other imaging exams.
On one side of the debate is Dr. Rebecca Smith-Bindman, who believes that it should be the job of the U.S. Food and Drug Administration to protect patients by regulating radiation from CT scanners. “Radiation doses are higher than they should be and they vary dramatically within and between facilities and that is not acceptable,” she said in the article.
Dr. Bruce Hillman, on the other hand, believes that the problem lies with doctors who order too many scans (which can lead to finding conditions that might have been better left untreated). And, according to the article, he thinks that “heaping more regulation on an industry that has already been squeezed by Medicare cuts may squelch the kind of innovation that produced CT scanners in the first place.”
In my opinion, there are three answers to this storm:
1. We need to make greater efforts to strive for appropriate use of CT. For that we can turn to the best authority available: the American College of Radiology Appropriateness Guidelines. Computerized decision support programs in electronic medical records can help, too.
2. We need to strive for much lower radiation dose per scan. We know that the dose per scan frequently can be reduced by up to 60 percent by the use of better CT techniques (selection of imaging parameters, shielding) and by modern CT technology. Here guidelines from organizations like the Society for Computed Body Tomography (SCBT/MR), an arm of the ACR, can be helpful and can drive education for all levels of healthcare providers.
3. We need to ensure that financial incentives leading to conflict of interest are minimized, so that patients can be comfortable that any CT scans are done only for appropriate diagnostic investigation.
Finally, in all the storm about cost and radiation fear, we need to remember that CT is a very powerful diagnostic tool that provides definitive information which can be used to save lives and select the best therapy quickly. It does far more good than harm — in every institution, every day.
In a recent New York Times article, Dr. Peter Libby, chief of cardiovascular medicine at the Brigham and Women’s Hospital in Boston, discusses the benefits versus the risks and costs of medical procedures like CT scans. In particular, he addresses the issue of incidentalomas, which occur when “medical scans pick up incidental findings that may be benign, leading to complications that make an otherwise healthy person ill.”
Dr. Libby writes, “While contemporary imaging modalities offer powerful and much needed tools for diagnosis and management when appropriately deployed, we should bear in mind the potential risks they entail if used indiscriminately.”
The problems created by incidentalomas is one area where you really need an expert: your radiologist.
This is what radiologists do – they don’t merely detect findings on CT scans, but also attach significance (or insignificance) to each finding.
When all your training and all your experience is in CT scans and their findings, you become pretty good at telling incidentalomas from true problems which need more investigation. Not perfect, of course, but pretty darn good.
In the past couple weeks there has been much talk about the cancer risk from medical radiation. According to a recent Reuters article, one chest CT scan delivers the same radiation (and risk) as 100 chest X-rays. However, these numbers still do not communicate the bigger picture: CT cancer risk can be more clearly explained.
Since most people never get close to getting 100 chest X-rays, we need to find a more common point of comparison. Driving, however, is something most North Americans do on a regular basis, and its risks are well-publicized.
43,000 people died in 2007 from car accidents in the U.S. During that same year, U.S. drivers drove 3 trillion miles, according to the U.S. Census Bureau. Based on these statistics, the risk of dying from driving 35,000 miles is about 1 in 2000 (0.05%).
An abdominal/pelvic CT scan delivers about 15 milliSieverts of radiation. In our calculations, using the most conservative data from the atomic bombings of Hiroshima and Nagasaki and the Chernobyl disaster, the risk of mortality from radiation-induced cancer is also about 1 in 2000 (0.05%).
Published data also supports this risk level: Brenner and Hall have estimated that the total lifetime attributable risk of death from cancer after receiving an abdominal CT with 240 mAs, is in the 0.06%-0.07% range (this estimate is for ages 15-25; CT risk drops radically after age 25).
Thus: If the average U.S. driver travels just under 14,000 miles per year… then the risk of dying in car accident (if only driving for 2 years, or 35,000 miles) is about the same as the lifetime risk of dying from cancer induced by the radiation in a CT of the abdomen and pelvis.
Of course, driving more carefully and lowering the CT dose per scan both are good ideas.
At the recent International Society for Computed Tomography (ISCT) meeting in San Francisco, studies were presented showing that CT scanning with a new algorithm, called model-based iterative reconstruction (MBIR), could offer better image quality and lower radiation dose than scanning with an adaptive statistical iterative reconstruction (ASIR).
According to AuntMinnie.com, “researchers claim that MBIR outperforms previous efforts to maximize the utility of low-dose CT exams, with researchers reporting excellent image quality and enhanced lesion conspicuity.”
University of Washington is one of the international sites for the multi-center trial of MBIR. My colleague, Paul Kinahan, was one of the two scientists who reported on MBIR images at the ISCT meeting.
We are very impressed with the technique here – it may someday result in a further huge dose reduction for CT. At this point it is in early stages of development and assessment of its clinical impact has not yet begun. But it looks very promising!
Last month, the American Association of Physicists in Medicine (AAPM) hosted national Dose Summit that focused on the need for standardization protocols for CT scanning, which would help to ensure patient safety and lower associated radiation risks during CT exams.
According to an e! Science News article, summit attendees included some of the world’s leading experts in CT imaging. Organizer Cynthia McCollough, Ph.D., said the summit “achieved its goal of identifying several issues that need to be dealt with by the medical imaging community in order to address the safety concerns of patients at U.S. hospitals and clinics.”
This summit also made progress in “developing consensus CT protocols and making them freely available via the Internet to hospitals and clinics across the United States.” CT protocols (or “imaging parameters”) define how equipment is used for certain procedures.
In my opinion, standardization of protocols is a powerful way to lower CT dose. In a recent study published in the Annals of Internal Medicine, adjacent hospitals in the San Francisco Bay area had a 13-fold difference in CT exam radiation dose for similar studies done for similar indications. The difference was all in the technique parameter selection.
With standardized protocols, groups of radiologists can get together to study how to do various types of CT exams with the lowest dose but yet still producing good diagnostic information. Once they agree on CT technique parameter selection with low dose as a goal, they can all use the same protocols and practices. This can dramatically lower the dose to a patient population – through standardization on best practices in CT.
One of the largest studies to date has confirmed the accuracy of CT scans for acute appendicitis in adults, which supports the use of CT for diagnostic and surgical means when risk for radiation exposure is low, according to findings published in a recent AuntMinnie.com article.
Dr. Perry Pickhardt, professor of Radiology at the University of Wisconsin, said that “at least three other studies confirmed that the negative appendectomy rate dropped from more than 20 percent to less than 10 percent with the use of CT… but one thing that was lacking was the actual diagnostic performance or accuracy with MDCT… so we looked at what I think is the largest CT-based cohort for appendicitis.”
Dr. Pickard presented this data at the International Society for Computed Tomography (ISCT) meeting I just attended in San Francisco.
This is a very good example of how CT can accurately prevent surgery when it is not needed while also guiding correct surgery when it will do a lot of good. In this application, CT is cost-effective and does a lot of good – way outweighing any (very low) risk from the radiation. For adults it is the diagnostic exam of choice in situations where signs and symptoms raise concern about possible appendicitis.
It’s a fact of life that all CT scans involve radiation. And certain types of diagnoses and diseases are going to require regular repeated CT scans – resulting in a high cumulative CT radiation dose to the patient over time. But as a recent news story profiled, there is a new technique and technology that can help reduce CT scan radiation exposure by up to 60%.
Researchers at the University of Washington have pushed the frontiers of CT technique by circumventing the noisiness and blurriness of images scanned at very low radiation dose. These noisy images are made sharp and clear by better software reconstruction technology. It’s a bit like what NASA does with high altitude satellite technology. This means that the same diagnostic power is achievable with much less radiation to the patient.
This new approach works for all types of CT scans, but can be especially important for children and certain areas of the body – in particular, the female breast, the gonads and other tissues in the abdomen. These are particularly radiation sensitive, so we want CT scans to be as low in radiation dose as possible without compromising the diagnostic power of the CT scan. Low dose technique combined with low dose technology accomplishes this.
New innovations are continually being made in the field of medical imaging. If you need a CT scan, it’s always OK to ask your doctor if you can get one with a lower dose of radiation.
Radiation is part of nature. We’re all exposed to radiation every day in very small amounts. But the amount of radiation being used for medical diagnosis has been increasing over the last 20 years or so – to a point where it is now raising new concerns about CT scan risks. In fact, the use of CT has increased over the last decade to the point where we’re now doing around 60 million CT scans a year in the United States.
So what does this mean for patients?
What other options are available to minimize the effects of CT scans?
How can patients go about trying to make smart decisions about the risks and benefits of CT scans?
Last October, I took part in a Webinar for Patient Power with medical physicist Dr. Kalpana Kanal that addresses these questions and more – touching on radiation dosage and risk, new technologies, and techniques for limiting exposure.
Findings presented by researchers at the Radiological Society of North America’s RSNA 2009 event are shining new light on the importance of understanding cost effectiveness in CT scan use. In particular, I had the opportunity to design and perform a study that showed how the high negative predictive value of ECG-gated cardiac CT in low- to moderate-risk chest painpatients may allow an earlier yet safe discharge from an emergency department (ED) at a considerable cost savings.
For example, the standard of care for chest pain is an ECG, a blood test and a nuclear stress test – which keep a patient in the ED an estimated 30 hours and can cost as much as $8,000. A gated cardiac coronary CT angiogram (CCTA) done instead early during the ER visit could rule out coronary artery stenosis plus other causes of chest pain, resulting in the safe discharge of a patient in just five hours at a cost of about $4,000.
But it’s not just about finding ways to lower costs. By avoiding the nuclear test and doing a low dose CT, patients also reduce the total radiation dose – resulting in a safer overall procedure.
And this is just one example of the benefits that can be found in reexaminating some of the traditional approaches to diagnosis and medical imaging.