Squeezing the most from X-rays.
The radiologic community in the United States has come somewhat late to the party as regards concern over radiation exposure in diagnostic imaging. Years ago, in travels to Europe and Japan, I was informed about the high level of public and medical anxiety about the possible medical repercussions from the ever increasing use of X-rays. Computed tomography (CT) had been around for more than 20 years and its diagnostic utility, and therefore steadily increasing use, were quite evident. In fact, CT was the major source of medical radiation received by the population and therefore a logical target for exposure management. In more recent years, the U.S. population and radiologic community have gotten behind "the cause" by looking for ways to better modulate the ionizing radiation dose administered for CT examinations and the overall medical radiation exposure to the population.
In my own practice, in an emergency department and trauma center, the use of CT has skyrocketed in recent years, particularly with the advent of more detectors and more applications. The total-body CT survey used in major blunt trauma is a staple of our practice because it allows quick, accurate diagnosis, leading to an earlier discharge, and it precludes other less-reliable diagnostic tests or surgical procedures. In the past we relied on such less-definitive methods because we did not have that diagnostic certainty.
There is a growing number of articles in our scientific imaging literature that discuss the efficacy of lower-dose regimens and the emphasis that the vendors have increasingly put on decreasing dose, while maintaining diagnostic image quality. These articles have certainly caught my attention and, I am sure, they have caught the attention of most of you as well. Physicians caring for children have appropriately been most focused on this issue, given the higher radiation sensitivity of their young patients. On the other hand, I also believed that as an emergency radiologist I really did not need to be too bothered by our heavy utilization of CT because, after all, we were addressing emergent and non-elective situations and, therefore, the ends justified the means. I was admittedly taken aback when I learned that a full-body CT scan was the equivalent to about 1000 chest radiographs. I became aware that while I was uneasy about this, I really did not know enough about the whole subject personally to understand either how worried I should be or what to do about it.
While I try in these editorials to offer the lighter side of issues in radiology and medicine, this discussion does not really lend itself to humor. Still, I suggest that you browse over to www.comics.com and check out the June 23, 2003, strip of one of my favorite cartoons, "Herman." The subject matter is perfectly germane to this discussion. (1)
Last month I was invited, as the Editor-in-Chief of Applied Radiology, to moderate a session on minimizing radiation risks in CT imaging. This seemed like a perfect opportunity to get a free trip to San Francisco, but also to do some indepth learning about this subject. The seminar and resulting roundtable discussion was a tour-de-force. We included a world-renowned radiation physicist, a cardiologist and four radiologists with a wealth of personal experience in the field. We also invited three PhDs from the industry to speak about their current implementations and future ideas for improved radiation dose efficacy.
This entire discussion will be presented as a supplemental issue of Applied Radiology in November and it will also be featured in a series of Webinars. The meeting was a state-of-the-art synthesis of current thinking and practice as regards radiation use in CT scanning.
While I will not describe any of the details in this format, I would like to leave our readers with some overall impressions.
We still do not know the clinical significance, if any, of diagnostic radiation. As reflected in two past Applied Radiology editorials, there are strong arguments on both sides. (2,3) As professional radiologists, we have decided to adopt a conservative approach on this and move toward controlling radiation exposure (decrease) as much as possible while performing clinically needed and diagnostically acceptable imaging.
There is a great deal of controversy regarding what we should be measuring to determine biologically meaningful exposure, what terminology should be used in describing radiation exposure, and how standardized guidelines for exposure could or should be established.
CT manufacturers recognize the importance of this issue and are clearly targeting radiation measurement and dose optimalization as worthy efforts to promote their machines. They are coming up with some very impressive technology that will progressively lower dose for a given study.
Radiologists, in general, are probably not as familiar with current concepts of radiation biology, dose modulation techniques and optimizing dose requirements for particular clinical situations as they need to be. Mass education efforts require improvement.
Our clinical referrers, in most cases, have little specific knowledge about the potential harm of medical radiation, the need for tighter control in "susceptible" patients, and the import of formulating a particular clinical question in the decision to use ionizing radiation vs. other imaging techniques. They generally do not grasp the reasons why we must modify the CT dose appropriate to a given clinical problem.
Radiation exposure and dose modulation strategies need to receive more attention during radiology residency training. Radiology departments should have ongoing programs, as part of quality control, to monitor radiation exposure as compared to national and internationally established ranges for equipment, examination type and patient-specific factors. They should have an ongoing policy of achieving as-low-as-possible exposure.
A method to track individual patient dose over time is necessary to guide future use of medical radiation.
These are just a few points worthy of our attention that arose from this meeting. There is a wealth of specific information that will be of use to radiologists who desire to improve their knowledge on this subject. Perhaps this editorial will, to some extent, spur organized radiology to support or at least discuss some of the concepts mentioned above.
(1.) Unger J. Available at http://comics.com/search/?Search=radiation&Per Page=10. Herman. June 23, 2003. Accessed May 26, 2009. Copyright Laughing Stock International Inc., Distributed by United Media.
(2.) Siegel E. Primum non-nocere: A call for re-evaluation of radiation doses used in CT. Appl Radiol. 2006;35(4):6-8
(3.) Mezrich R. A contrarian view of X-ray doses: It ain't necessarily so. Appl Radiol. 2006;35(5):6-8.
Stuart E. Mirvis, MD, FACR
Dr. Mirvis is the Editor-in-Chief of this journal and a Professor of Radiology, Diagnostic Imaging Department, University of Maryland School of Medicine, Baltimore, MD.
|Printer friendly Cite/link Email Feedback|
|Author:||Mirvis, Stuart E.|
|Date:||Jun 1, 2009|
|Previous Article:||Advances in high-field MR imaging of the spine.|
|Next Article:||Knowing right from left on x-rays: a way to minimize errors of laterality.|