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 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.”
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.
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.”
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.
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 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 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.
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 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.
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.
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.
“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 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.
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.