B.D. Giordano, J.F. Baumhauer, T.L. Morgan, and G.R. Rechtine II reply:
Drs. Opreanu and Kepros bring up an excellent point regarding the relative radiosensitivity of the various tissues exposed during diagnostic imaging. As we note in our study, when c-arm fluoroscopy is used to image a body area in the normal mode, technique factors are adjusted automatically according to the tissue density and cross-sectional area. Therefore, during imaging of larger, denser body areas such as the pelvis or spine, technique factors may be increased by a considerable margin, thus subjecting not only the bones and muscles but also the more radiosensitive, underlying visceral organs to elevated levels of radiation. These body areas are routinely imaged with use of c-arm fluoroscopy during both elective orthopaedic and trauma surgical procedures. In separate publications, we examined radiation exposure to the patient and surgical team during imaging of the cervical spine1,2. In conjunction with this current publication, our data suggest that even more vigilance must be practiced when imaging the musculoskeletal system adjacent to other especially susceptible body areas.
We believe that it is important to note that one cannot receive too little radiation over the course of one's lifetime. Regardless of the radiosensitivity of the biological tissues being exposed to ionizing radiation, reaching often cited maximal exposure limits (as set forth by regulatory boards such as the National Council on Radiation Protection and Measurements and the International Commission on Radiological Protection) should not be viewed as optimal or desirable. The readers should be aware that these values have been modified throughout the years, and that international standards are stricter than those imposed in the U.S. When discussing risks associated with radiation exposure, many authors first look at the maximum allowable exposure limits and then extrapolate backward to determine how many cases may be performed on a patient before exceeding these limits. In like fashion, Drs. Opreanu and Kepros frame their sentiments relative to threshold levels, which in our study and many other studies are not reached for the surgeon or surgical team. We think that this manner of reasoning should be reversed. The question we should ask ourselves is, "How can I change my practice to minimize radiation exposure to my patients and myself?" rather than "How many procedures can I do before I exceed my yearly exposure limit?"
We again remind the reader that the concept of ALARA (As Low As Reasonably Achievable) should be followed at all times. While the exposure levels capable of producing deterministic effects are well known, the cumulative effects of consistent radiation exposure remain unknown. As we point out, epidemiological data suggest that exposure to as "little" as 5 to 10 rem over a lifetime increases the risk of developing cancer3. This figure applies to both physicians and patients. Interestingly, when we used a highly sensitive portable ion chamber to measure background scatter (even twenty feet from the testing zone), it still recorded 200 µrem/hr during mini-c-arm imaging. While this dose is seemingly inconsequential, it highlights the fact that scatter radiation is present even at great distances from the radiation source and is not zero as some believe. Furthermore, although a radiation dosimeter badge may report that 0 mrem are detected, this is often not the case. Many dosimeters begin registering exposure at 10 mrem. Thus, exposure below this level is reported as 0 mrem.
Our study seeks to bring awareness to the fact that the use of fluoroscopy in medicine for indirect visualization is not without risk. As the use of fluoroscopy becomes more and more commonplace in daily practice, we must continue to scrutinize the detrimental effects that its use may pose to our patients and ourselves. Often, physicians and surgeons have no idea how much radiation a patient is exposed to during procedural or diagnostic imaging. Furthermore, many find it difficult to apply exposure levels to an understandable frame of reference that makes such levels relevant and meaningful. Rather than using threshold values to determine the number of allowable procedures per year, our hope is that physicians and surgeons will begin to alter their practice habits and work backward from a "worst-case scenario" when considering the safety aspects of radiation exposure. That is, they should carefully scrutinize the necessity for imaging studies, consider alternative imaging modalities, limit the use of live fluoroscopy in the operating room, collimate images, always use protective equipment, consistently practice dose reducing techniques, etc.
These letters originally appeared, in slightly different form, on . They are still available on the web site in conjunction with the article to which they refer.