Answer to Question #7406 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:

Three years ago at age 39, I had a helical 1.25 mm CT through the chest and abdomen with peak aortic enhancement.

Could you tell me the approximate dose of radiation I received? What is my cancer risk now? Is it safe for me to have more CT scans of the chest and abdomen if needed?

I have read that CT scans are more dangerous for women, which concerns me.

CT (computerized tomography) technology has changed greatly in the last several years, so it is difficult to estimate any dose without knowledge of the actual scan protocol, which varies between hospitals, the CT scanner model, and the manufacturer, etc. Also it is becoming more common to scan chest-abdomen, abdomen-pelvis, or chest-abdomen-pelvis all at once due to advancements in CT technology.

I would estimate the total effective dose (ED) for a chest-abdomen CT to be approximately 16.7 mSv, where the ED for only the chest exam is 7.4 mSv and for the abdomen CT only is 9.4 mSv. The average ED for a chest CT is 7 mSv with a range of 4.0-18.0 mSv reported in literature. For an abdomen CT, the average ED is 8 mSv with a range of 3.5-25 mSv reported in literature.

The cancer risk cannot be estimated for an individual case because each person is different in terms of radiation sensitivity and response. One important consideration is the benefit you derive from CT scans, as an accurate diagnosis from a CT scan far outweighs the risks of not having diagnostic information. In recent months there have been articles discussing breast cancer risks from standard cardiac scans (Einstein et al. 2007) in which lifetime cancer risk is estimated to be 0.7 percent for a 20-year-old female. Another way to look at this is that the risk of not developing cancer is 99.3 percent from standard cardiac scans.

Terry T. Yoshizumi, PhD

Reference
Einstein AJ, Henzlova MJ, Rajagopalan S. Estimating risk of cancer associated with radiation exposure from 64-slice computed tomography coronary angiography. JAMA (298)317-323; 2007.

Answer posted on 28 April 2008. 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.