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20 March 2010

Answer to Question #7171 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'm concerned about the amount of radiation exposure I've had over the years for gastric issues. Up to date, I've had an upper and lower gastrointestinal (GI) series, one HIDA scan (hepatobiliary iminodiacetic acid scan—helps evaluate the function of the gallbladder and the bile ducts), an abdominal CT scan, and various x rays. My doctor would like me to undergo another HIDA scan for a suspected gallbladder issue. My question is, at what point should I be concerned about radiation?

I am sorry to hear about your health issues. The good news is that radiological procedures can reveal information to the radiologist that would otherwise only be determined by performing exploratory surgery. I have made a list of the exams that you mentioned with estimated doses from a reliable Web site using a published reference.

Upper GI series — 0.15 rem
Lower GI series — 0.70 rem
HIDA scan — 0.315 rem
Abdominal CT — 1.2 rem

The total estimate of these exams is 2.4 rem. Other radiological exams are also in this range with dental and chest x rays delivering MUCH lower doses.

All medical procedures involve a risk-versus-benefit decision made by the doctor. The risk was small for the radiation exposure received compared to the benefit you received. As noted in the Health Physics Society Position Statement on "Radiation Risk in Perspective," there is no demonstrated health effect for radiation exposures below 5-10 rem (50-100 millisievert). Even if you have had additional radiological exams, your radiation dose to date is a fraction of the dose where there is any known potential for health effects. I would not be concerned if I had these exams. And you need to remember that you benefitted from the results of these exams by ruling in or ruling out diseases by a radiologist.

As you can see, the HIDA scan has a relatively low dose. Prior to the widespread use of radiopharmaceuticals, your doctor could have listened to your symptoms, decided that you had a gallbladder problem, and sent you to surgery. And they could have removed a perfectly functioning gallbladder which might not have been the cause of the problem. Nuclear medicine exams are very helpful in diagnosing disease.

You should always discuss the pros and cons of any procedure with your doctor. Also, there is much information on the Internet that looks reliable but, in fact, is inaccurate especially when providing radiological information.

I hope that this answers your concerns. I also hope that your doctor can find the source of your problem and help you to feel better soon.

Marcia Hartman, MS

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