Answer to Question #766 Submitted to "Ask the Experts"

Q

What regulations/standards are there to monitor and control radiation exposure to staff and patients in a hospital?

A

There are regulations that institutions within the United States have to follow to assure that people who are exposed to radiation because of their job keep their exposures low and below limits. Some of these occupational exposure limits are controlled by the state in which the person works and some by the Federal Nuclear Regulatory Commission. In general, the annual limits are 5 rem whole body, 15 rem to the lens of the eye, and 50 rem to any organ or to an extremity (rem is a term used for measuring the amount of dose a person receives). Persons who might, during the course of carrying out their job, be exposed to 10% of these limits (some regulations say 25%) must wear some form of radiation monitoring device. This device measures the amount of exposure the worker receives so when the institution receives the results of these devices, they can make sure everyone is below those dose limits. The institution is also required to share this information with the worker. Dose limits set by the Nuclear Regulatory Commission can be found at the NRC Web site under the Section 1201 link. You might be able to find specific state limitations at the Conference of Radiation Control Program Directors Web site and clicking on the link for "State radiation control programs." There also are consensus standards written by the National Council on Radiation Protection and Measurements (NCRP). While they do not carry the weight of law, most radiation safety people pay careful attention to their recommendations. The report describing the limits of radiation exposure is number 116 and can be ordered through the NCRP Web site.

As for patients, it isn't quite so direct. When a patient comes to a hospital and a radiation test is ordered, there is a trust that the physician has determined the test to be necessary, that is, justifiable. The benefit of the test must outweigh any risk associated with the exposure. So there are no limits for the amount of exposure a patient can receive, at least from that standpoint. There are "behind the scenes" limits. For instance, we have to routinely measure the output of all of our x-ray tubes and make sure they are operating appropriately. We do the same with equipment in nuclear medicine. We must make sure the lowest possible dose is used to get the best picture possible. We also have a responsibility to use another test if it will obtain the same or better information (e.g., ultrasound, MRI). In the case of my institution (I think nearly every institution does this but I have not verified it), we use national study results to compare our exposures. For instance, if national study results say that the effective dose for a chest x ray should be between 0.005 and 0.05 mrem, then we make sure our doses meet or are below those doses. The Food and Drug Administration also has regulations regarding x-ray tube quality control standards. These can be found on the FDA Web site. The Conference of Radiation Control Program Directors Web site listed in the first paragraph might also have some information on quality control of x-ray tubes.

Kelly Classic
Certified Medical Health Physicist