Answer to Question #7856 Submitted to "Ask the Experts"

My question involves a veterinary hospital where I was employed a number of years ago. I worked at this veterinary hospital for about seven years, but only one day a week for the most part, approximately eight hours a week. I had not given the x-ray equipment they had there much thought until now. The floor plan of this hospital was very open, not really any doors that sealed off rooms. I am unable to provide the model of the machine or the material of the wall that was behind the equipment. Thinking back, the only shielding I could account for visibly was a lead shield, probably 2.1 meters tall and 1.2 meters across at the one end of the machine that would be exposed to the public. This area where the machine was was not fully enclosed by four walls or a door. However, nobody was in the area when it was in use, except the animal technicians holding the animal during the x ray. 

My questions: Are there different (perhaps less strict) regulations in shielding that companion animal practitioners must follow for their equipment? Is there lower "energy" involved in taking x rays of animals? In my time there, I was probably in the building for about two x rays per month, although more were done obviously when I was not there. I did not perform any x rays and was never in the same room. Should I be concerned with the amount of scatter radiation I may have been exposed to over that time period? Being in another room at the time, does that weaken the amount of radiation I may have been exposed to? With technicians standing in front of the machine with lead aprons, does that block some of the radiation that could have escaped? How far can scatter radiation really travel throughout a small building?

I apologize for the length of my question, but this has really weighed on my mind for quite some time.

The short answer to your question is that you have nothing to be concerned about based on the descriptions in your question.

Veterinary facilities are usually planned and reviewed in a manner similar to medical facilities. In some respects, the regulations for veterinary x ray are not as stringent due to the patient not being human, lower workloads (amount of x ray used, x rays typically at a lower energy), etc. The radiation safety regulations for the state in which this facility is located should address radiation dose limits to radiation workers and members of the general public. X-ray rooms are typically designed to keep radiation doses below these limits by using shielding, institutional controls, or a combination of the two.

Typically, the x-ray machine is a radiographic unit in a fixed installation, usually within a room. Although not as common, it is possible to see an installation as you described that is still acceptable from a radiation safety standpoint. This is evident by your description where you indicated that no one was ever within a set distance from the x-ray unit during exposures (except the person taking the x rays).

Conceivably, you would have received a very small amount of radiation dose from scatter radiation from each x ray you were present for. Since you were located at a distance from the x-ray unit, the radiation dose levels were significantly lower than if you were located nearer the unit (if you double your distance from the x-ray source, your dose drops to one-fourth, and so on), and therefore were not large enough to be of any concern.

Based on your description, it sounds as if the facility followed safe radiation safety practices during x-ray use. Although the open configuration may not be typical, radiation doses were controlled due to following safe operating procedures such as keeping everyone away from the area during exposures, having a mobile shield adjacent to public occupied areas, and providing a lead apron for the operator.

Ken "Duke" Lovins, CHP