Dr. Mirvis is the Editor-in-Chief of Applied Radiology and a Professor of Radiology, Diagnostic Imaging Department, University of Maryland School of Medicine, Baltimore, MD.
We picked the topic of minimizing radiation risk in computed tomography (CT) imaging because it is extremely timely. Looking at the literature of today, we can see a large number of papers that address the issue of radiation exposure. It is my hope that the contents of this supplement toApplied Radiology will arm radiologists with recommendations that help them and their nonradiology colleagues better manage radiation exposure. We have assembled an expert panel to discuss their viewpoints on this topic.
CT is a very popular and powerful diagnostic tool. Our clinicians, our referring base, certainly appreciate its power and order many CT studies as part of patient management. The challenge is that we are irradiating patients and giving them 50% of the total dose the U.S.population will receive annually.
This supplement will address several major questions. What should we be measuring and what is biologically relevant?
How do we track radiation exposure to a patient? Do we ever step in and say that a patient has reached their lifetime limit of CT scans?
How do we modify what we do, either technically or in the way we perform CT studies, so that we obtain the lowest possible exposure and without compromising diagnosis?
How do we inform a patient about the risks of radiation, when maybe we ourselves do not even know what informed consent is? Does everyone need to have consent, or are there only selected circumstances where patients need to have informed consent for a procedure? In doing so, do we risk creating an overreaction, maybe by inciting more fear than is justified? Could this preclude the use of CT in a situation where it may be very important, where the risk-to-benefit ratio is obviously tilted toward benefit?
How do we educate the physicians who order these studies? And who decides what is indicated? Do radiologists have a role to play in that area?
Media focus on CT radiation
The U.S. Food and Drug Administration (FDA) has an online CT resource (http://www.fda.gov/cdrh/ct/) with a comparison of radiation exposure between various modalities. Most notably, it provides the comparison of chest X-ray and CT. The site states that a CT of the abdomen is equivalent to 500 chest X-rays. In my practice, we do a lot of abdominal CT, and it is somewhat mind-blowing to look at the fact that such a common procedure is equivalent to approximately 3.3 years of background radiation.
The figures should be taken in the proper clinical context. Unfortunately, much of the research has fueled what I would call “alarmist” media. The National Academies of the Sciences, National Research Council published a report in 2005 (Health Risks from Exposure to Low Levels of Ionizing Radiation: BEIR VII Phase 2) about low-levels of ionizing radiation and its contribution to cancer risk. The contention was that a body CT increases a patient’s chances of developing a radiation-induced cancer by 1 in 1000. One in 1000 is a pretty long odd. I do not think any of us would bet on a 1-in-1000 horse at Preakness.
I was interested in radiation exposure in the emergency center, and I found an article combining data from Orlando Regional Medical Center, Orlando, FL, and Washington Hospital Center, Washington, DC.1 They indicated that 12% of the ER population, over a 5-year period, received more than 100 mSv of radiation.
What risk are we inducing in this population of what we would call repeat business, people who often will come back to the emergency room for their care, and who tend to get a lot of radiation exposure? A recent study in Radiation Research indicated that there was no relationship, in the study population, between radiation exposure and risk of cancer, leukemia or solid tumors.2 The study could not attribute any risk specifically to diagnostic radiology.
So with that, we will now let our panel of experts explain the details about how we cope with, and optimize,radiation dose in clinical practice.
- Cumulative radiation exposure shows increased cancer risk for emergency department patients. Science Centric. May 22, 2008. http://www.sciencecentric.com/news/article.php?q=08052224. Accessesed on November 9, 2009.
- Hammer GP, Seidenbusch MC, Schneider K, etal. A cohort study of childhood cancer incidence after postnatal diagnostic X-ray exposure. Radiat Res. 2009;171:504-512.