Vascular - CT Protocols - CTisus.com CT Scanning

Vascular ❯ CTA Runoff Study

CT Protocol for CTA Runoff Study

Problem	The reason for the study can vary from evaluation of PAD (peripheral arterial disease), to pre-operative planning for a flap (fibular graft and flap planning) to suspected aneurysm/pseudoaneurysm to tumor evaluation to evaluation post trauma. The specific scanning protocols including area volume scanned and scan timing as well as single or dual phase imaging will vary depending on the clinical application. Dual energy imaging is often valuable especially for bone removal in vascular mapping.
Protocol	The area scanned if only the lower extremities are to be evaluated will vary but typically will go from just above the iliac crests thru the feet. We will routinely especially in older patients do a second run from above the knee thru the feet. Our delay is usually 30 seconds and the 2nd run will help in cases with decreased flow thru at least one of the lower extremities. We inject 100-120 cc of Iohexol-350 at 5 cc/sec and reconstruct with thin sections (under 1mm) at.5 mm intervals. We routinely will use dual energy techniques when available to help with automatic bone removal. Images will require 3D mapping and we routinely use MIP and VRT images. In cases where the entire aorta is evaluated (from neck thru feet) one should consider increasing the volume of IV contrast.
Pearls	the area scanned will depend on the clinical application and clinical question CTA runoff studies are often challenging in older patients due to extent of vascular calcification dual energy CT helps with bone removal and can also decrease artifact in patients with hardware in place (i.e. total hip or total knee replacement) analysis of muscle mass is important on these studies as well trauma applications often require careful attention to the venous map and to the presence of AV shunting the timing of these studies is critical and is especially challenging in older patients in cases with bone removal we typically create a video loop for the referring clinicians in patients with diabetes and small vessel calcification the study is especially challenging