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PURPOSE To facilitate the scan plan of high pitch(Turbo-flash)dual-source coronary CT angiography under high heart rates by analyzing the endsystolic reconstruction phases in prospective ECG-triggered acquisitions.METHOD AND MATERIALS 14 patients with heart rate higher than 65-90 bpm underwent the third generation dual-source coronary CT angiography.End systolic reconstructions were performed at every 10 ms from 200 ms to 450 ms after R wave.Based on the American Heart Association coronary segmentation guidelines,the image quality of S1,S2,S3,S5,S6,S7,S8,S11,and S13 was analyzed by two radiologists with 5 point Likert scales(1-2,poor; 3,fair; 4,good; 5,excellent).According to the Z-axis acquisition slabs,these segments were divided into three groups.Group 1 included S1,S5,S6 and S11; group 2 included S2 and S7; group 3 included S3,S8 and S13.The initial phase,the end phase with fair image quality,and the temporal window between the two phases were recorded.RESULTS The heart rates were between 65 and 89 bpm,the mean heart rate was 77±7.3 bpm.The initial phases of the three groups were 200-280(211±18.53)ms,200-330(235±39.77)ms and 200-290(240±35.55)ms,respectively.There was significantly statistical difference between group 1 and 2,as well as group 1 and 3.The end phases of the three groups were 320-450(404±30.97)ms,310-450(393±35.55)ms and 310-450(383±36.34)ms,respectively.There was significantly statistical difference only between group 1 and 3.For the initial phases,there was a gradual delay from group 1 to 3,while the end phase of group 3 was the earliest,followed by group 2 and group 1.The temporal window of the three groups were 90-250(193±39.37)ms,60-250(158±58.67)ms and 40-250(143±56.78)ms,respectively.There was significantly statistical difference between group 1 and 2,as well as group 1 and 3.There was a trend of narrowing in temporal window from group 1 to 3.CONCLUSION In patients with high heart rates,the end-systolic reconstruction phases of the three Z-axis slabs are relatively regular,so we may use cauda-cranial scan direction and the middle end-systolic phase(250-290 ms)as a trigger time for Turbo-Flash scan mode.