Abdominal aortic aneurysm: Can the arterial phase at CT evaluation after endovascular repair be eliminated to reduce radiation dose?

Abstract

Conclusion: The arterial phase of computed tomography (CT) imaging is not necessary for routine detection of endoleaks. This portion of CT evaluation after endovascular AAA repair can be eliminated, with a reduction in radiation exposure. Summary: This was a retrospective analysis performed of arterial and venous phases of CT scans evaluating for endoleak in patients with endovascular repair of an abdominal aortic aneurysm (AAA). The purpose was to determine if the arterial phase of CT scanning for evaluation of endoleak can be potentially eliminated, thus lowering radiation exposure. The authors analyzed 85 patients (66 men and 19 women; mean age, 66 years) who underwent endovascular repair of an AAA. There were 110 multidetector CT examinations available for analysis. The CT protocol for endoleak evaluation included first obtaining a noncontrast, enhanced set of CT images. After this, intravenous contrast material was administered, and both arterial and venous phase images were obtained. Nonenhanced and venous phase images were evaluated to determine if an endoleak was present. Arterial phase images were analyzed separately. It was then determined how often the arterial phase imaging contributed to the diagnosis of endoleak. A total of 28 type II endoleaks were detected with a combination of nonenhanced and venous phase CT acquisitions. Of these 28 endoleaks, 25 endoleaks were also visualized during the arterial phase of the CT scan, with three type II endoleaks only seen during the venous phase. No additional endoleaks were seen with the arterial phase. Seventy-eight scans from 67 patients revealed no endoleak during the venous phase; and in these scans, no endoleaks were discovered with the arterial phase images. The arterial phase of the CT scan was responsible for 36.5% of the radiation exposure during the combination of noncontrast, venous, and arterial phase images. Comment: The radiation administered during a diagnostic CT scan is associated with low, but not zero, health risk. This radiation has been linked to an increase in life-long risk of cancer (Radiology 2004;232:735-8). Because type II endoleaks are relatively benign, the increased radiation dose of arterial phase acquisitions does not seem warranted. Additional data are required to know whether the arterial phase acquisitions may, however, remain necessary to detect small type I or type III endoleaks.