NEW YORK (Reuters Health) – The radiation dose and, thus the cancer risk, during CT coronary calcification screening varies widely depending on the testing protocol used, according to study findings in the Archives of Internal Medicine for July 13.

Multidetector CT has been evaluated as a screening tool for coronary calcification in asymptomatic individuals, Dr. Kwang Pyo Kim, from the National Cancer Institute, Bethesda, Maryland, and colleagues explain. A screening program using this modality would likely entail testing tens of millions of people, but there is currently limited data regarding estimated radiation doses and risk of radiation-induced cancer.

Dr. Kim’s team addressed this issue by calculating the radiation doses given to adult patients under various protocols using Monte Carlo radiation transport modeling. Data for the modeling was derived from medically exposed cohorts and Japanese atomic bomb survivors.

The effective dose for CT coronary calcification testing ranged from 0.8 to 10.5 mSv. Correlates of higher radiation doses included higher x-ray tube current, higher tube potential, spiral scanning with low pitch, and retrospective gating, the report indicates.

Because of the wide variation in the estimated radiation dose, the estimated risk of cancer also varied widely. Assuming a dose of 2.3 mSv, if a man were to be screened every 5 years from 45 to 75 years of age; or a woman from 55 to 75 years, the estimated excess lifetime risks of cancer would be 42 (range 14 to 200) and 62 (range 21 to 300) per 100,000 men and women, respectively.

“For patients in whom coronary artery calcification scoring is considered, healthcare providers should ideally discuss the potential risks and benefits of the procedure,” Dr. Raymond J. Gibbons and Dr. Thomas C. Gerber, from the Mayo Clinic, Rochester, Minnesota, comment in a related editorial. “This discussion should include the small radiation risk described by Kim et al.”

Reference:
Arch Intern Med 2009;169:1185-1186,1188-1194.