Aaron David Sodickson MD, PhD, Presenter: Nothing to Disclose

Pieter Frederic Baeyens MD, Abstract Co-Author: Nothing to Disclose

Luciano Monte Serrat Prevedello MD, Abstract Co-Author: Nothing to Disclose

Richard D. Nawfel PhD, Abstract Co-Author: Nothing to Disclose

Katherine P. Andriole PhD, Abstract Co-Author: Medical Advisory Board, General Electric Company Medical Advisory Board, TeraMedica, Inc

Ramin Khorasani MD, Abstract Co-Author: Stockholder, Medicalis Corp Global Advisory Board, General Electric Company Global Advisory Board, EMC Corp Medical Advisory Board, Medicalis Corp

To survey cumulative diagnostic radiation exposures and estimated lifetime-attributable-risk (LAR) of radiation-induced cancer in adult patients undergoing CT imaging.

The study cohort comprised all patients who underwent diagnostic CT in 2007 at a 752-bed tertiary academic medical center. We searched the administrative database for all CT scans performed in the cohort in the prior 22 years. We calculated each patient’s cumulative CT radiation exposure by summing typical effective dose values for the anatomic regions scanned, and used the Biological Effects of Ionizing Radiation (BEIR-VII) methodology to estimate the LAR of cancer incidence and mortality based on the patient’s gender and the age at each exposure. We did not assign a dose value to scans with widely variable doses, and did not include scans performed outside our institution.

We captured 190,918 CT studies in 31,533 patients. Median, mean, and maximum individual study counts were 3, 6.1, and 132, respectively, with 33% undergoing greater than 5 lifetime CT scans and 6% greater than 20. Median, mean, and maximum cumulative effective doses were 24 mSv, 54 mSv and 1375 mSv respectively, with 15% of patients receiving over 100 mSv, and 4% receiving over 250 mSv. The associated cumulative LAR had median, mean, and maximum values of 1/759, 1/321, and 1/8 respectively, for cancer incidence, and 1/1201, 1/510, and 1/15 respectively, for cancer mortality. For a cohort of this size, the expected baseline cancer rate of 42% predicts 13,244 cancers. In comparison, our mean calculated LARs estimate that CT imaging of this cohort will produce 98 radiation-induced cancers, including 62 fatal cancers.

Recurrent CT radiation exposure added incrementally to baseline cancer risk in the cohort, though we underestimate lifetime exposures. While most patients accrue low radiation-induced cancer risks, there is a subgroup potentially at higher risk due to more numerous recurrent CT scans. Further work is needed to refine the exposure estimation model and to explore the impact of various CT dose reduction strategies both on the population as a whole, and on this higher-risk subgroup.

Risks of radiation-induced cancer may be estimated at the level of the individual patient by incorporating a historical review of CT imaging, and the BEIR-VII risk models.

Sodickson, A, Baeyens, P, Prevedello, L, Nawfel, R, Andriole, K, Khorasani, R, Recurrent CT Imaging, Cumulative Radiation Exposures, and Associated Radiation-induced Cancer Risks at a Tertiary Care Academic Institution.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6008371.html