Vascular - CT Protocols - CTisus.com CT Scanning

Vascular ❯ Abdominal Aortic Aneurysm (AAA)

Problem

Evaluation of the patient with suspected or known abdominal aortic aneurysm (AAA).

Protocol

The optimal protocol is a single phase contrast enhanced CT scan from diaphragm to symphysis pubis. In select cases the upper and lower limits of the scan may be extended based on the prescan topogram or the lowest scan thru the pelvis. The scan is usually a single phase acquisition with a 30-35 second scan delay after injecting 100-120 cc om ioxehol at a rate of 4-5cc a second. The need for a second run will be dependent on factors including the presence of dissection, the possibility of a leaking AAA or even delayed renal function. All images are reviewed with axial, and coronal and sagittal images. Many sites like ours find that 3D volume rendering and MIP imaging can be very helpful especially in complex cases.

Pearls

The key to a successful exam often is tailoring the protocol to the specific patient. Prior scans when available can be very helpful. Other factors include;

careful analysis of the branch vessels including the celiac, SMA, Ima and renal arteries is critical
comment on renal function and any asymmetry can be important. Do not miss renal artery stenosis or fibrous muscular dysplasia
the use of 3D imaging is especially valuable to the surgeon if the patient becomes a surgical candidate
if there is a question of a leak or active bleed then a delayed scan following the first run is critical
relationship of the aorta and spine is especially important in cases of mycotic aneurysm
non contrast scan are usually of little value except in patient with prior surgery especially with endovascular stent repair (EVSR)
careful attention to medially placed linear calcification as a sign of dissection is critical
maximum aortic size can usually be done on axial images unless the aorta is very tortuous then center line measurements are needed.