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John W. Gofman, M.D., Ph.D., Professor Emeritus,
Molecular and Cell Biology, Univ. Calif. Berkeley
and Egan O'Connor, Exec. Director, CNR and XaHP.
XaHP Document 107, October 2000
XaHP: The X-rays and Health Project.
An educational project of the
Committee for Nuclear Responsibility.
* Part 1. Proposal: An Expert Consultation by Physicists
* Radiologists in Toronto invited a team of medical physicists to observe their actual x-ray imaging practices, to measure doses, to teach low-dose techniques, to tune-up existing equipment, and to ensure proper processing of exposed films. Radiologists are the experts in interpreting the medical meaning of x-ray images, whereas medical physicists have special expertise in the physics and mathematics of making the images.
* The result in Toronto? The consultation demonstrated that --- without loss of image-quality --- average dose could be reduced "by a factor of at least 3 with little work and by a factor of 10 or more if all conditions are optimized" (Taylor 1983, p.557). These achievements were obtained without purchases of major new equipment.
* If the Toronto radiologists assumed, before the consultation, that doses at their facilities were already as low as technically possible, their assumption was demonstrably mistaken.
* This is still the case, according to Joel E. Gray, Ph.D., medical physicist, who recently retired from the Mayo Clinic to become a consultant based in Danbury, Connecticut. Dr. Gray warns radiologists that "If your exposures have not been measured recently, you cannot be sure what exposures you are using" (Gray 1998a, p.61).
* "Techniques for reducing radiation exposure in angiography and fluoroscopy are relatively simple, inexpensive, and easily applied to general radiographic imaging," according to Gray (Gray 1998b, p.62). Like Dr. Taylor, he asserts that images have equal or better quality after proper dose-reducing measures. He also recommends specific ways to reduce dosage during CT scans (1998a).
* CT scans, and procedures employing fluoroscopy, account for the overwhelming share of patient-exposure (Gray 1998a, p.63). Therefore, they deserve the first attention from consultants on dose-reduction per procedure.
* Part 2. Who Could Perform Such a Consultation?
* In the USA, there are several thousand certified medical/health physicists having expertise in the physics of x-ray imaging. Which among them might be best qualified and available to perform on-site "Toronto-type" consultations? For advice on that question, one might start by contacting Dr. Joel Gray or possibly Fred A. Mettler, Jr., M.D., Chief of Radiology at the University of New Mexico School of Medicine in Albuquerque. Useful referrals might also be available from the University of Wisconsin Radiation Calibration Lab in Madison (Keith A. Kunugi, at 608-262-6320).
* Part 3. Who Would Pay for Such a Consultation?
* To pay for the initial on-site consultation and follow-up visits, we believe that a foundation which supports community health would almost certainly provide a grant via some tax-deductible (501-c-3) health group in the nearby area. The consultation would be an appropriate educational project, promoting better health in the community. What is learned from the first consultation could be shared, as the Toronto information was shared.
* It is not possible to obtain a current cost-estimate until a group of radiologists decides to participate. Medical physicists can hardly produce an estimate, without knowing the size of a practice, its existing equipment and staff, and the location(s).
* Would any group of radiologists want not to participate in a consultation for learning if and how doses in its practice could be further reduced?
* We are confident that all radiologists would prefer to deliver the undeniable benefits of x-ray imaging with the least chance of causing an x-ray induced cancer later on. Radiologists are certainly dedicated to helping patients. And for that reason, it would be a major asset for any radiological practice to be able to certify to patients that it (a) makes regular reality-checks on the assumed doses which it gives; (b) pays close attention to dose-reduction; and (c) gives no more dose than necessary. Lastly, a community which encourages such practices will improve its health.
- Gray 1998a (Sept), Joel E., "Lower Radiation Exposure Improves Patient Safety," in Diagnostic Imaging Vol.20, No.9: 61-64.
- Gray 1998b (Oct), Joel E., "Optimize X-Ray Systems to Minimize Radiation Dose," Diagnostic Imaging Vol.20, No.10: 62-70.
- Taylor 1979, Kenneth W. et al., "Variations in X-Ray Exposures to Patients," Journal of the Canadian Assn. of Radiologists Vol.30: 6-11.
- Taylor 1983, Kenneth W., "Diagnostic Radiology," Chapter 16 in The Physics of Radiology, Fourth Edition, edited by H.E. Johns and J.R. Cunningham. Springfield IL: Charles C. Thomas, publisher.