Answer to Question #8077 Submitted to "Ask the Experts"

Category: Nuclear Medicine Patient Issues — Diagnostic Nuclear Medicine

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

Ask the Experts is posting answers using only SI (the International System of Units) in accordance with international practice. To convert these to traditional units we have prepared a conversion table. You can also view a diagram to help put the radiation information presented in this question and answer in perspective. Explanations of radiation terms can be found here.
Answer posted on 2 April 2009. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.