Answer to Question #7532 Submitted to "Ask the Experts"
The following question was answered by an expert in the appropriate field:
Recently I had a CT (computerized tomography) heart scan for a calcium score. It was done in two separate scans, heart and the whole chest area. It was a 64-slice scan which the radiologist said gave a dose of 9 mSv. He added that that is the radiation equivalent of four hours on the beach. The results were normal, but I feel somewhat weak, nervous, and uncomfortable in the chest region and lung areas. I am a bit confused about the comparison the radiologist gave me. Is my concern about any damage to the lungs well founded?
You are correct that the comparison of your exposures to background radiation is in error. We generally quote an average background radiation exposure value of 3 mSv/year. If your exposure was 9 mSv, it would equate to an effective dose of three years of background radiation.
Regarding your exposure, information from the Radiology Info website indicates the effective dose for a calcium scoring exam is 3 mSv. This value may not be correct as the technique listed indicates only one CT scan. If the second study you had was for a diagnostic chest CT, the table of doses from various radiological procedures lists the effective dose as 7 mSv. As these are representative values, the total value of 9 mSv you were told is reasonable, as radiation output from CT scanners does vary.
Regarding your symptoms, I doubt they are related to your radiation exposure. Many epidemiological studies show no demonstrated effects below 10 mSv. See the Health Physics Society Position Statement titled "Radiation Risk in Perspective". I would recommend that you contact your physician. Your symptoms may be related to an underlying medical condition.
John Jacobus, MS
Certified Health Physicist
Ask the Experts is posting information 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.