Answer to Question #8077 Submitted to "Ask the Experts"
The following question was answered by an expert in the appropriate field:
I had a nuclear bone scan. The administered activity was 925 MBq. What was my exposure from this scan? My understanding is that the bladder gets much more radiation exposure than the rest of the body. If I started drinking right away and drank more and more and used the restroom several times during the two-hour wait, did that help? Is the following accurate?
Bladder wall, 2-hour void, 0.7 mSv/MBq
Bladder wall, 4.8-hour void, 1.67 mSv/MBq
The total effective dose for your study is 5.27 mSv. Every person is different and since you drank a lot of water, you probably received a lower dose, although I don't know exactly how much lower.
The information that you list from the package insert is correct for a person who receives 740 MBq and holds his/her bladder and does not go to the bathroom for two hours. For someone who receives 925 MBq and holds his/her bladder for two hours, the bladder dose would be 32.5 mSv. Since you started drinking water and going to the bathroom as soon as possible, your dose was definitely lower than that.
So you did as well as a person could to reduce the dose from radiation.
All medical procedures involve a risk-versus-benefit decision made by the doctor. The risk is small for the radiation exposure compared to the benefit you received. As noted in the Health Physics Society Position Statement "Radiation Risk in Perspective," there is no demonstrated health effect for radiation exposures below 50-100 mSv.
Marcia Hartman, MS