Optimal scanning protocols of 64-slice CT angiography in coronary artery stents: an in vitro phantom study.

PURPOSE The purpose of the study was to investigate the optimal scanning protocol of 64-slice CT angiography for assessment of coronary artery stents based on a phantom study. MATERIALS AND METHODS Coronary stents with a diameter of 2.5mm was implanted in thin plastic tubes with an inner diameter of 3.0mm to simulate a coronary artery. The tubes were filled with iodinated contrast medium diluted to 178HU, closed at both ends and positioned in a plastic container filled with vegetable oil (-70 to -100HU). A series of scans were performed with a 64-slice CT scanner with the following protocols: section thickness: 0.67mm, 1.0mm, 1.5mm, 2.0mm, pitch value: 0.2, 0.3, 0.5 and reconstruction interval of 50% overlap of the section thickness. 2D axial and multiplanar reformatted images were generated to assess the visibility of stent lumen, while virtual intravascular endoscopy (VIE) was reconstructed to evaluate the artery wall and stent surface. RESULTS Our results showed that a scanning protocol of 1.0mm slice thickness with a pitch of 0.3 produced acceptable images with best demonstration of the intrastent lumen and stent surface with minimal image noise or artifacts. In contrast, submillimeter scans with 0.67mm resulted in moderate artifacts which affected visualization of the coronary lumen, in addition to the increased noise. When the section thickness increased to 1.5mm and 2.0mm, visualization of the artery wall and stent surface was compromised, although the intrastent lumen was still visible. CONCLUSION Our in vitro study suggested that a scanning protocol of 1.0mm section thickness with pitch of 0.3 is the optimal protocol for evaluation of coronary artery stents as it allows generation of acceptable images with better visualization of stent lumen, stent surface and coronary artery wall.