Thomas G. Flohr PhD, Presenter: Employee, Siemens AG, Forchheim, Germany

Bernhard Schmidt PhD, Abstract Co-Author: Employee, Siemens AG

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

Christian Eusemann PhD, Abstract Co-Author: Employee, Siemens AG

Cynthia H. McCollough PhD, Abstract Co-Author: Research grant, Siemens AG

Determine image noise and motion artifact levels for single-heart beat, cardiac CT angiography using spiral cardiac DSCT and pitch=3.2.

A 4mm diameter artery phantom containing a coronary stent was placed in a thoracic phantom and moved at an angle of 45° relative to the scan plane using a computer-controlled motion device. Clinically realistic motion patterns were simulated at heart rates of 60, 70 and 90bpm. ECG-triggered dual source cardiac CT spiral (pitch=3.2) and ECG-triggered sequential scans were each acquired using 120kV, 160mAs per rotation per tube, and a 0.28s rotation time, resulting in a nominal temporal resolution of 75ms. For pitch=3.2, the resulting table feed was 430mm/s. While ECG-triggered sequential scanning provides phase-consistent images, ECG-triggered spiral scanning results in a slight phase change between images adjacent in the z-direction. Axial and multiplanar reformatted image were reconstructed at a slice thickness of 0.75mm and a 0.5mm increment using a medium sharp (B46) kernel. Motion artifacts were assessed by visual inspection. Image noise was measured in a homogenous central region of the phantom.

artifacts at all three heart rates. In the ECG-triggered, pitch=3.2 spiral mode, images were visually free of motion artifacts at 60 and 70 bpm, however image quality was degraded due to motion at 90 bpm. In the absence of motion artifact, all images had equivalent image noise and sharpness and observers were able to assess the in-stent lumen and to resolve the struts of the coronary stent.

At 60 and 70bpm, pitch=3.2 spiral cardiac scanning provided artifact free images of a moving coronary artery phantom at equivalent image noise as an ECG-triggered sequential scan. While temporal resolution per image remained constant at 75ms for both scan modes and all heart rates, at 90bpm the time needed to scan the artery phantom was longer than the low motion period within diastole, resulting in motion artifact.

 For heart rates < 70bpm, pitch 3.2, ECG-triggered spiral cardiac DSCT can scan the entire heart in one beat at equivalent image quality and lower dose relative to ECG-triggered sequential cardiac CT.

Flohr, T, Schmidt, B, Allmendinger, T, Eusemann, C, McCollough, C, Image Noise and Motion Artifact Susceptibility for a Novel, Pitch=3.2 Spiral Cardiac Dual-Source CT (DSCT) Scan Mode.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8011216.html