RESUMO
One of the newest CT application technologies is cardiac synchronized image reconstruction. In this technology, evaluation of time-resolution is very important. We developed a method of measuring time-resolution in cardiac synchronized reconstruction, and evaluated various scanning protocols. In our experiment, ECG-gated scanning was done by multi-slice CT (Aquilion16 Super Heart Edition, Toshiba Medical Systems Co., Ltd., Japan). The nominal slice thickness was 0.5 mm, and rotation time was 0.5 sec. Input heart rate was set at 40, 45, 50, 55, 60, 70, 75, 80, and 90 bpm, and helical pitch at 3.2, 4.0, and 4.8 (beam-pitch: 0.200, 0.250 and 0.300). We measured FWTM of the obtained sensitivity distribution and compared at each scanning protocol. Time resolution improved as helical pitch decreased and heart rate increased. However, phase-time resolution deteriorated as heart rate increased. The results of our experiment indicated that a segment center was determined by X-ray tube rotation time and heart rate, and the number of segments was determined by heart rate, helical pitch, and reconstruction position. Time resolution changed with X-ray tube rotation time, heart rate, helical pitch, and reconstruction position. In this report, we provide a reference for an optimal scanning protocol in cardiac synchronized image reconstruction.
