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

Abstract

Purpose: The purpose of the studywas to investigate the optimal scanning protocol of 64-slice CT angiographyfor 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 tubeswith an inner diameter of 3.0mm to simulate a coronary artery. The tubes were filled with iodinatedcontrast medium diluted to 178HU, closed at both ends and positioned in a plastic container filled withvegetable oil (-70 to -100 HU). A series of scans were performed with a 64-slice CT scanner with thefollowing protocols: section thickness: 0.67mm, 1.0mm, 1.5mm, 2.0mm, pitch value: 0.2, 0.3, 0.5 andreconstruction interval of 50% overlap of the section thickness. 2D axial and multiplanar reformattedimageswere 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 1.0mmslice thickness with a pitch of 0.3 producedacceptable images with best demonstration of the intrastent lumen and stent surface with minimal imagenoise or artifacts. In contrast, submillimeter scans with 0.67mm resulted in moderate artifacts whichaffected visualization of the coronary lumen, in addition to the increased noise. When the section thicknessincreased to 1.5mmand 2.0mm, visualization of the arterywall and stent surfacewas compromised,although the intrastent lumen was still visible.Conclusion: Our in vitro study suggested that a scanning protocol of 1.0mm section thickness with pitchof 0.3 is the optimal protocol for evaluation of coronary artery stents as it allows generation of acceptableimages with better visualization of stent lumen, stent surface and coronary artery wall.