Masao Kiguchi RT, Presenter: Nothing to Disclose

Eiji Nishimaru RT, PHD, Abstract Co-Author: Nothing to Disclose

Yotaro Ishihara MS, Abstract Co-Author: Employee, General Electric Company

Chikako Fujioka RT, Abstract Co-Author: Nothing to Disclose

Kazushi Yokomachi RT, Abstract Co-Author: Nothing to Disclose

Kazuo Awai MD, Abstract Co-Author: Research grant, Toshiba Corporation Research grant, Hitachi, Ltd Research grant, Bayer AG

Minoru Ishifuro, Abstract Co-Author: Nothing to Disclose

Yasushi Nagata MD, Abstract Co-Author: Nothing to Disclose

Overlapped image reconstruction is now possible at prospective ECG-triggered CT (ECG-triggered step-and-shoot scanning). We assessed the resolution and the variability of the quality of images by using prospective ECG-triggered scans and overlapped reconstruction in a phantom study.

We obtained prospective (step-and-shoot) scans on a 64-detector CT (GE) using a slit phantom (slit pitch 0.55, 0.5, 0.45, and 0.4 mm), coronary artery plaque models (4-mm diameter) with different levels of stenosis (area 18, 50, and 82%) and density (-20 HU, simulating soft plaques), and a stent phantom (Cypher®, 4-mm diameter) with artificial 50% in-stent restenosis on a pulsating cardiac phantom. We performed non-overlapped- and overlapped reconstruction of 0.625 mm thickness at 0.3125 mm pitch increments. We evaluated slit resolution of the profile curves with the contrast scale method, the full width at half maximum (FWHM) of the profile curve of the stent phantom, and the image quality (graded subjectively by visual ranking) of coronary artery plaques using the normalized-rank approach.

The average of the profile curve contrast on the slit phantom of prospective overlapped (-0.18, -0.17, -0.13, -0.08) and non-overlapped (-0.18, -0.16, -0.13, -0.08) scans was similar. The FWHM of the profile curve of the stent phantom on overlapped- and non-overlapped scans was 0.98 and 1.00 mm, respectively; the difference was not statistically significant (p=0.69, t-test). The normalized rank of the visual score for the plaque and stent phantom was 0.736 and 1.0294 at overlapped- and -0.736 and 0.234 at non-overlapped reconstruction, respectively (p<0.01).

Overlapped reconstruction images from prospective ECG-triggered scans were of comparable resolution and higher visual quality than non-overlapped reconstruction images.

Overlapped reconstruction of prospective ECG-triggered scans can achieve a radiation dose reduction at CT coronary angiography without degradation of image resolution and quality.

Kiguchi, M, Nishimaru, E, Ishihara, Y, Fujioka, C, Yokomachi, K, Awai, K, Ishifuro, M, Nagata, Y, Quantitative Assessment of Spatial Resolution along Z-axis on Overlapped-Reconstruction Images Obtained at Prospective ECG-triggered Cardiac CT.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11003750.html