Is cumulative dose of importance when tracking CT use for adult patient stone assessment?

Posted on September 20, 2019 by Kalpana Kanal

Guest Post by: Kalpana Kanal, PhD

In a recent article published online (1), the authors investigated CT utilization and cumulative radiation dose in adult stone patients over a period of 3 years. In their analysis, patients were classified as “active” (≥ 2 diagnosis codes for nephrolithiasis, or receipt of stone surgery) or “inactive” (one stone diagnosis) and compared to age- and gender-matched controls. The authors concluded that CT use and non-surgical radiation exposure for active stone patients is significant, with over 10% estimated to exceed occupational limits (50 mSv annually) in the first year. They further mentioned that for active stone patients, mean 3-year estimated cumulative CT-related radiation was 28.3 ± 28.5 mSv for operative patients and 22.0 ± 24.4 mSv for non-operative patients. As has been previously mentioned in a blog I wrote in 2016 (2), there is support for tracking cumulative dose (3) as well as thought that cumulative dose should not be given any importance when making decisions about individual patients (4, 5). The linear no-threshold 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. Low dose techniques should be used for repeated CT scans to minimize dose to the patients. Educating our colleagues about the benefits of CT as well as its utilization and use of low dose KUB scans for repeat stone assessment would reduce dose to these patients, but using cumulative dose as a reason for not using CT is not appropriate.

References:

Jessica C. Dai, Helena C. Chang , Sarah K. Holt , Jonathan D. Harper , National trends in CT utilization and estimated CT-related radiation exposure in the evaluation and follow-up of stone patients, Urology (2019), doi: https://doi.org/10.1016/j.urology.2019.07.030.
Kanal KM – https://blogs.uw.edu/radwblog/2016/04/11/should-cumulative-radiation-dose-be-tracked/
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 of 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.

CT Dose Management Across Radiology

Posted on June 18, 2018 by William Shuman, MD

This superb article emphasizes the very high importance of a team approach when undertaking CT dose management.

CT radiation dose reduction for patients with pulmonary invasive fungal infection

Posted on April 18, 2018 by William Shuman, MD

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.

Patients need information to prepare for their imaging exams – how will they obtain it?

Posted on February 15, 2018 by William Shuman, MD

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.

Helping Patients Understand Radiology Reports

Posted on January 4, 2018 by William Shuman, MD

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 Value of Oral Contrast from the patient’s point of view

Posted on September 13, 2017 by William Shuman, MD

Oral Contrast

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.”

Optimizing CT Radiation Doses Across Institutions Leads to Dose Reductions

Posted on April 14, 2017 by William Shuman, MD

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

Posted on April 12, 2017 by William Shuman, MD

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

CT technique and technology

Posted on February 6, 2017 by William Shuman, MD

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.

Decreasing radiation dose in CT for COPD patients

Posted on June 8, 2016 by William Shuman, MD

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

Posted on April 20, 2016 by William Shuman, MD

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?

Posted on April 11, 2016 by William Shuman, MD

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 patients^{3, 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:

Communicating with Patients

Posted on February 17, 2016 by William Shuman, MD

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.

Jenny Favinger with patient at SKC Oct 2015

Radiologist at free clinic

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

Reducing dose for CT pulmonary angiography

Posted on November 13, 2015 by William Shuman, MD

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

Posted on October 30, 2015 by William Shuman, MD

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.

Radiation Dose Management in CT: Is it easy to accomplish?

Posted on September 4, 2015 by William Shuman, MD

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.

The importance of dose alerts

Posted on August 24, 2015 by William Shuman, MD

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.

Low radiation dose without compromise of image quality

Posted on March 27, 2015 by William Shuman, MD

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.

Achieving appropriate radiation dose for coronary CT angiography

Posted on October 2, 2014 by William Shuman, MD

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.

Optimizing Radiation Dose

Posted on August 28, 2014 by William Shuman, MD

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.

CT radiation dose reduction by iterative reconstruction in lymphoma staging

Posted on June 24, 2014 by William Shuman, MD

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.

Educating patients about radiation dose

Posted on June 23, 2014 by William Shuman, MD

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.

Patient Resource: Radiation Risk Calculator

Posted on May 5, 2011 by William Shuman

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…

CT Exams in Medical Records Becoming Realistic Goal

Posted on December 7, 2010 by William Shuman

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.

Educating Patients About Radiation Risk Not Always Easy

Posted on November 22, 2010 by William Shuman

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.

Shuman’s Spotlight on Low Radiation Dose CT

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