Answer to Question #14499 Submitted to "Ask the Experts"

I am an intern in a medical college. I was posted in urology operating theatre (OT) on my first day. I didn't know that a PCNL (percutaneous nephrolithotomy) procedure was being done at some point of time in the OT. I can't remember, but I was standing at 1.2 to 1.5 m from the operating table without any protective equipment for 20 to 30 minutes while the operation was conducted. None of my seniors or staff told me anything about the procedure, about lead aprons, etc. After some time, I realized that something was wrong and left the room. What are my risks for serious consequences form such a single encounter?

These types of situations sometimes arise and can create some undue concern. While it isn't possible to determine exactly how much radiation exposure you received during this procedure, I'm quite confident that it was really pretty low and certainly not enough to cause any consequences. Allow me to elaborate a bit on that conclusion.

I'm not familiar with the procedure you mention; however, presumably it is performed utilizing fluoroscopy (you never really said that, but it's a logical conclusion from your concerns). Radiation exposure to staff during any fluoroscopy procedure depends on a number of factors including the time the fluoroscopy unit is actually being used, the size of the x-ray field impinging on the patient, the location of the x-ray tube during the procedure (e.g., under table, above table, lateral projection, etc.), the location of staff members, etc. The mantra of radiation protection is "time, distance, and shielding." So, in this case, the first two factors, time and distance, most likely work to your advantage in terms of what your exposure may have been. Unless this is an unusually complicated procedure, I suspect the actual fluoroscopy time is pretty low (perhaps 5 to 10 minutes) since the procedure itself lasted about 20 to 30 minutes. The radiation exposure to staff mainly comes from scatter from the patient and as one moves further from the patient, the radiation exposure drops off significantly. Being 1.2 to 1.5 meters away would result in a fairly significant reduction in radiation exposure. For example, the exposure at 1.2 meters from the patient would be approximately one-fourth of what the exposure would be at 0.6 meters from the patient. Typically, staff actively involved in the procedure may need to be very close to the patient (e.g., within 0.3 m), thus the need for lead (Pb) aprons to provide some protection to those up close to the procedure.

Requirements vary in different states in terms of the use of lead (Pb) aprons to protect staff. In the state where I practiced health physics for many years, the requirement was that Pb aprons were required for anyone exposed to the "direct scatter" from the patient. While one could be exposed to the direct scatter 15.2 m away if there was a direct line of sight to the patient, due to the distance effect mentioned above, we typically required Pb aprons for anyone within 1.8 to 3.0 m of the patient. Based on measurements and personnel monitoring that we performed, we saw very little radiation exposure at distances greater than 1.8 m away, and that was for multiple procedures. While you were within that distance, your exposure still would have likely been very low, especially for a single procedure. Should this situation occur in the future, one way to protect yourself is to simply stand behind someone wearing a Pb apron. By doing so, you not only are protected by that person's Pb apron, but the person's body would also provide considerable shielding for you.

You should check with an individual responsible for radiation safety at your facility (i.e., the radiation safety officer) to determine the specific requirements for the use of Pb aprons. It may also be advisable to ask at the beginning of procedures you're not familiar with if radiation is used for that procedure.

So, you need not concern yourself about the consequences from what little exposure you may have received from this single procedure.

Mack L. Richard, MS, CHP