Optimizing CT Radiation Doses Across Institutions Leads to Dose Reductions

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.”

 

Patients’ awareness of radiation dose and risks associated with medical imaging

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.

Revolution CT Scanner at UW Medical Center Department of Radiology

 

New National Dose Levels Established for Common CT Exams

Dr. Kanal’s Research Establishes New National Dose Levels for Common CT Exams

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.

Decreasing radiation dose in CT for COPD patients

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.

The effect of trauma backboards on CT radiation dose

This article provides another neat bit of knowledge to consider when looking for lowest dose – though this is multi-factorial.

[Excerpt below]Backboard use in ED Figure 6

“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.”

Should cumulative radiation dose be tracked?

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.

References:

  1. 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.
  2. 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.
  3. 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.
  4. 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.

Low-dose Radiation

Low-dose Radiation Not Harmful

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.
UW Medicine Physicists

UW Medicine Physicists

Detection of pulmonary nodules with low-dose CT and iterative reconstruction

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.

Low-dose CT enterography

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.)

Reducing dose for CT pulmonary angiography

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.

Gentle and wise use of CT radiation dose

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.

The importance of dose alerts

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.

 

CT Colonography: Reducing the Radiation Dose

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.

Low dose CT Revolution scanner

Seattle King5 TV’s Jean Enerson reported recently on UW Medical Center’s installation of the GE Revolution CT scanner.

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:

    • TAVR
    • All aortograms
    • Cardiac
      • 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)

 

Low radiation dose without compromise of image quality

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.

Annual screening for lung cancer low-dose CT

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.

Radiation protection shielding

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.

Educating patients about radiation dose

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.

Significant radiation dose reduction without sacrificing image quality

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.

RSNA 2011 Relections

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!

UW’s Team Approach to Radiation Dosage Reduction

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!

CT Scans in the ER: Generally a Safe Practice

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.

Thoughts on Radiation Exposure, Risk

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?

CT Radiation Overexposure Still a Problem, Regulation Issues are Complex

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.

Interview: Recent Discovery of Radiation in Milk Not Cause for Concern

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.

CT Appropriateness Key to Usage, Understanding Risk

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.

Patients Want To Know About Radiation Risks

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.

Communication Networks Help Avoid Repeat CT Scans

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.

Upcoming CT Speaking Engagements

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!

Radiation Bill Signed Into Law

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.

CT Perfusion Dose – What is all the Hue and Cry About?

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.

Low Dose CT for Cardiac Imaging

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.

Keeping Patients Up To Date

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:

1. RadiologyInfo.org

2. “How to Explain Radiation Risk” from the Washington State Department of Health

3. Wanzhen Zeng’s “Communicating Radiation Exposure: A Simple Approach

Is Treatment Necessary? Ask a Radiologist.

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.

Measuring Risk: Driving vs. CT

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.

New Algorithm Provides Lower Radiation Dose, Better Image Quality

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!

CT Radiation Risks Outweighed When Preventing, Guiding Acute Appendicitis Surgery

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.