Thomas Werncke MD, DIPLPHYS, Presenter: Nothing to Disclose

Mathias Wittmann MD, Abstract Co-Author: Nothing to Disclose

Matthias Taupitz MD, PhD, Abstract Co-Author: Nothing to Disclose

Frank K. Wacker MD, Abstract Co-Author: Research Grant, Siemens AG

Bernhard C. Meyer, Abstract Co-Author: Nothing to Disclose

Abdominal aortic aneurysms (AAA) change the hemodynamic situation in the arteries of the lower extremity. Therefore the purpose of this study was to assess the influence of different table feeds (TF) on vascular enhancement and image quality in patients with an AAA undergoing CT-Angiography in the lower extremity (runoff CTA).

In this retrospective IRB approved study 79 patients (71±8y) with an AAA (>30mm) who underwent a runoff-CTA between 01/04 and 08/11 were included. CTA was conducted using a 16 row-CT (n=24,120kV;140mAs, tRot:0.5s) and a 64 row-CT (n=55,120kV;120mAs, tRot:0.33s). TF ranged between 30-86mm/s as part of the institutional optimization process. Arterial enhancement was assessed by one reader in the runoff arteries with highest enhancement in 12 segments in one leg per patient. Image quality in terms of bolus timing was rated by two blinded readers (6y experience in reading CTA) using a 5 point scale (optimal (opt), acquisition slow and diagnostic (ART1) or non-diagnostic (ART2); mild (VEN1) or compromising venous enhancement (VEN2)) in the aorta, pelvis, thigh, calf and foot.

TF was categorized in quartiles: TF1(32.5±1.7mm/s), TF2(38.9±1.4mm/s), TF3(43.9±3.1mm/s) and TF4(57.4±10.8mm/s).  AAA diameter (54±15mm) was equal in all groups (p=0.4). Aortic enhancement was 370±20HU. Between aorta and fibular trunc arterial enhancement was comparable in the TF1-3 groups and lower for TF4. At the calf and foot best enhancement was noted for TF1 (288±80HU, 230±90HU) and TF2 (292±128HU, 209±119HU) and decreased from TF3 (256±104HU, 178±80HU) to TF4 (163±136HU, 114±93HU), p<0.01. Image quality was assessed in 695 segments (Interobserver agreement κ=0.82). In the aorta and pelvis all segments were rated OPT. In the thigh ART2 was noted only in 5% of the segments in TF3. In the calf ART2 was comparable in TF1-TF3(calf:<10%) and highest in TF4(25%). In the foot ART2 increased from TF1(10%) to TF4(41%) while VEN2 was comparable for TF1-TF3 and not present for TF4.

Runoff-CTA in patients with AAA revealed excellent results for all TF-groups above the knee. Below the knee, the results of this study indicate that highest image quality may be obtained using table feeds ranging between 30-40mm/s, whereas higher table feeds lead to a reduced image quality.

Run-off CTA in patients with an AAA is feasible using a robust acquisition protocol based on a constant table feed.

Werncke, T, Wittmann, M, Taupitz, M, Wacker, F, Meyer, B, Run-off CT-Angiography in Patients with an Aortic Aneurysm—Is There an Optimal Acquisition Strategy?.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12030455.html