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06 September 2008

Answer to Question #2971 Submitted to "Ask the Experts"

Category: Medical and Dental Patient Issues — Diagnostic X Ray and CT

The following question was answered by an expert in the appropriate field:

I am a 23-year-old female and have had the following exams done: (1) Head CT (approximately 10 years ago)
(1) Upper GI (approximately 2 years ago)
(2) Chest x rays (approximately 1.5 years ago)
(1) Chest x ray (approximately 6 months ago)
(1) Sinus CT (approximately 4 months ago)
(1) PET/CT (combined neck, chest, abdomen, pelvis)(approximately 1 month ago) Approximately how much radiation have I been exposed to in terms of rads? In particular, how much have I been exposed to in just the PET/CT alone (since this is a relatively new procedure)? I have asked the radiologists performing the exams and they seem to be providing "guesstimates." Can you help me? Also what are my chances of developing cancer or tumors?

I would give the following rough estimates of effective dose for the exams you mention. I give these doses in mSv and rem (see our dose FAQ for a further explanation of some of these units). Most of these dose estimates came from ICRP publication 62; some came from other unpublished data that I have access to.

(1) Head CT 1.8 mSv	=	0.18 rem
(1) Upper GI 4.5 mSv	=	0.45 rem
(2) Chest x rays 0.08 mSv	=	0.008 rem
(1) Chest x ray 0.04 mSv	=	0.004 rem
(1) Sinus CT 1.8 mSv	=	0.18 rem
(1) PET/CT 8.2 mSv	=	0.82 rem

I'm assuming that the PET/CT was an F-18 FDG study. I refer you to a previously answered question on this topic in which the risks of these procedures, with comparison to normal everyday exposures to natural radiation, are discussed.

Michael G. Stabin, PhD, CHP

Answer posted on 18 September 2003. The information and material posted on this Web site is intended as general reference information only. Specific facts and circumstances may alter the concepts and applications of 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 specific to whatever facts and circumstances are presented in any given situation. Answers are correct at the time they are posted on the Web site. Be advised that over time, some requirements could change, new data could be made available, or Internet links could change. For answers that have been posted for several months or longer, please check the current status of the posted information prior to using the responses for specific applications.