Tobias Gassenmaier MD, Presenter: Nothing to Disclose

Nils Petri, Abstract Co-Author: Nothing to Disclose

Thomas Allmendinger, Abstract Co-Author: Employee, Siemens AG

Thomas G. Flohr PhD, Abstract Co-Author: Employee, Siemens AG

David Christian Maintz MD, Abstract Co-Author: Nothing to Disclose

Wolfram Voelker MD, Abstract Co-Author: Nothing to Disclose

Thorsten Alexander Bley MD, Abstract Co-Author: Nothing to Disclose

To evaluate the influence of cardiac motion during coronary CT angiography on coronary stent visualization in a third generation dual-source CT scanner.

13 coronary stents (diameter 3.0 mm) were implanted in plastic tubes filled with contrast (density 350 HU) and attached to a phantom heart model. This phantom model was an elastic, contrast filled, anatomic heart model made of silicone, driven by a pump for pulsatile flow, resulting in alternating expansion and contraction of the phantom, comparable to a beating heart in humans. The phantom’s expansion rate was 74/min and an ECG simulator was connected to the scanner for a corresponding ECG signal. Scans were performed in an orientation parallel to the scanner’s z-axis and acquired in a retrospectively ECG-gated cardiac spiral (collimation 96x0.6 mm, tube voltage 120 kVp, 340 mAs tube current). Evaluation was performed using a medium-sharp (Bv49) convolution kernel optimized for vascular imaging at a static phase at maximum expansion, and at maximum motion, defined as midway between maximum expansion and contraction. Axial reformations of all stents were used for evaluation (window width 1500 HU, center 300 HU).

Mean visible stent lumen was significantly higher in the static phase of the phantom model with 65.6 ± 5.7 % (range: 54.4 – 76.7%) compared to 60.8 ± 4.4% (range: 51.1 – 66.7%) at maximum motion (p < 0.001). Mean in-stent attenuation was 346 ± 29 HU (range: 311 – 405 HU) in the static phase and 397 ± 66 HU (range 268 – 549 HU) at maximum motion. This difference with more realistic, i.e. closer to the actual contrast density of 350 HU, attenuation values in the static phase also proved to be significant (p = 0.004). Attenuation in the un-stented tube did not differ between standstill and motion (p = 0.48).

Stent lumen visualization is still impaired by cardiac motion in third generation dual-source CT scanners, but visible lumen diameter is only mildly affected and remains at an acceptable level in this in vitro setting. CTA may therefore be a valid method for detecting in-stent restenosis even in patients with higher heart rate or arrhythmia.

Motion artifacts are a challenge in coronary CT angiography. Increased temporal resolution of upcoming CT scanners may allow sufficient evaluation of coronary stents even during cardiac motion phases.

Gassenmaier, T, Petri, N, Allmendinger, T, Flohr, T, Maintz, D, Voelker, W, Bley, T, Influence of Cardiac Motion on Stent Visualization in Third Generation Dual-source CT: In Vitro Evaluation of 13 Coronary Stents in a Pulsating Phantom Heart Model.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14045636.html