Cumulative radiation exposure during thoracic endovascular aneurysm repair and subsequent follow-up

Thoracic endovascular aneurysm repair (TEVAR) is an appealing alternative to the standard surgical approach, but requires rigorous radiological follow-up. The cumulative radiation exposure (RE) of patients undergoing TEVAR-including pre-operative workup, the procedure and subsequent follow-up computed tomography (CT) imaging-has not previously been investigated.

From August 2003 to February 2011, 48 patients underwent TEVAR at our institution. Mean age was 66 ± 11 years, with 10 patients (21%) aged <60 years. Forty-one (85%) patients were male; 7 (15%) had urgent/emergent operation; 21 (44%) had undergone previous aortic surgery. Mean aortic diameter was 7.3 ± 2.1 cm. Intra-operative screening time and RE were reviewed, and typical institutional thoracic CT scan RE was calculated (17.8 mSv). Life expectancy of an age- and sex-matched population was estimated to assess the cumulative RE from recurrent CT follow-up.

The average screening time was 15.7 ± 11.4 min, with an RE of 11.3 ± 9 mSv. Obese patients had significantly higher RE during TEVAR (Pearson's coefficient = 0.388, P = 0.019). The RE dropped from 14.9 ± 9.4 mSv to 8.6 ± 7.9 mSv (P = 0.033) after a hybrid suite was established. Our institutional TEVAR protocol involves one pre-operative thoracoabdominal CT scan and three follow-up thoracic CT scans for the first year, with a yearly evaluation thereafter. The life expectancy of an age- and sex-matched population was 17 years. A patient adhering to our surveillance protocol would be subjected to an overall exposure of 89 mSv at 1 year and 161 mSv at 5 years, with a projected lifetime RE >350 mSv.

A 2-year RE exceeding the threshold of 100 mSv with a life expectancy >15 years can be estimated to lead to a lifetime risk increase in radiation-induced leukaemia and solid-tumour cancer >2.7%. The risks of cumulative RE especially in younger and/or obese patients must be balanced with the expected morbidity and mortality reduction in TEVAR versus traditional open repair, and the anticipated benefits of recurrent radiographic imaging.