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It’s time for radiology departments to eliminate lead shields when performing X-ray exams, medical physicists at the University of Colorado School of Medicine in Aurora contend. They explain why technological changes in X-ray equipment have negated the assumption that shielding improves patient safety and made decades-old federal regulations obsolete in the April 2019 issue of the American Journal of Roentgenology.
“Discontinuing the use of patient shielding will be a significant departure from how radiology has been practiced for decades,” wrote Rebecca M. Marsh, PhD, a medical physicist and associate professor of radiology, and Michael Silosky, an assistant professor of radiology. “Although change is difficult, it is incumbent on radiologic technologists, medical physicists, and radiologists to finally step up as reasonable voices on the subject.”
Patient shielding was introduced into the U.S. Code of Federal Regulations in 1976, and the wording has not changed in the ensuing 42 years.1 At the time, the regulation was intended to protect against the hereditary risks of radiation exposure. However, no hereditary effects have been observed in humans since then, according to the authors.
Since 1959, radiation dose exposure from X-ray exams to the testes and ovaries has dropped by 96%.2 The authors point out the amount of protection shielding provides varies based on whether anatomy is located outside or within the imaging field of view (FOV). Shielding anatomy outside the imaging FOV provides negligible protection because it cannot protect against internal scatter generated within a patient.
More importantly, shields may interfere with the function of automatic exposure controls. If they obstruct the imaging FOV, the radiographic system may drastically increase the tube output to try to penetrate the shield, resulting in an increased dose to the patient and a marked degradation in image quality. Retakes may be required, or an interpreting radiologist may be required to make a diagnosis from a less-than-optimized image.
The authors recommend that patients be informed prior to their examination that patient shielding is not provided because evidence shows shielding can actually increase radiation risk while providing negligible or no benefit. Technologists should be trained to provide information addressing patient questions and/or concerns. They should have the authority to provide shielding in cases where they believe that patients would benefit psychologically. The authors also recommend that radiology facilities employ posters and/or brochures to explain why shielding is no longer appropriate.
"All of the recent conversations about patient shielding are centered around patient safety,” Dr. Marsh told Applied Radiology. “After considering all of the available evidence, it is our opinion that discontinuing the use of patient shielding in diagnostic imaging is what's best for patients."
U.S. Food and Drug Administration, U.S. Department of Health and Human Services. CFR Code of Federal Regulations Title 21 (21CFR1000.50). 1976 and 2018. https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=1000.50. Accessed April 12, 2019.
Marsh RM, Silosky M. Patient shielding in diagnostic imaging: Discontinuing a legacy practice. AJR 2019;212(4):755-757.