低心率及心率变异下前门控CT冠状动脉造影中重叠时间设置的临床研究

Padding Time Setting for Prospective ECG Gating in Computed Tomographic Coronary Angiography:A Clinical Study of Low Heart Rate and Heart Rate Variability

目的采用前瞻性心电门控技术行低心率患者冠状动脉CT成像（CTCA），探讨重叠时间（PT）设置的临床应用价值。方法本研究共选取拟行CTCA检查的患者160例（心率≤55次／min，心率变异≤5次／min），依据患者体重指数选择管电流（270～800mA）、管电压设置为120kV。PT设置范围在0—150ms，每间隔10ms纳入10例患者。绘制受试者工作特征曲线（ROC）推断不同门设置下冠状动脉节段可评估性的切点。采用X2检验比较切点前后冠状动脉节段可评估率差异；分析心率与图像质量、辐射剂量的相关性。结果共有2257支冠状动脉节段参与评分，冠状动脉评分（4．55±0．66）分；ROC曲线显示不同胛设置下冠状动脉节段可评估性的切点为40ms，〈40ms与t〉40ms者冠状动脉节段可评估率比较：96．2％％VS99．2％（X2=23．751，P=0．000），差异具有统计学意义；PT设置与图像质量、辐射剂量呈正相关。结论在低心率及心率变异度下前瞻性心电门控技术可将PT设置修改为40ms可获得满足诊断的图像，同时降低辐射剂量。

Objective To evaluate value of padding time setting in coronary artery computed tomographic angiography with prospectively gated axial （PGA） CT technique at low heart rate （ ~〈65 beats per minute, bpm）. Methods 160 pa- tients with heart rates（HR） （54.51 ± 6.66）bpm（ range ：42 -- 65 bpm） was evaluated in this retrospective study. All pa- tients used PGA CT technique （tube voltage was 120 kV and tube current tailored to BMI）. The patient enrolled in subset by every 10 ms with the padding time（PT） setting（0 - 150 ms）. The PT of ≤40 ms and 〉40 ms was compared with per- eentage of assessable coronary artery segments by Chi-Square test. To evaluate the relationship between PT and image quali- ty or radiation dose by spearman or pearson correlation analysis. Results There were 2257 coronary artery segments to be evaluated. The mean image quality score was 4.55 ＋ 0.66. Below a PT of 40ms, as determined by receiver operator charac- teristic（ROC） curve, 3.8% of coronary segments were non-diagnostic compared with 0.8% with PT of 〉 40 ms（ X2 = 23. 751 ,P = 0. 000）. The relationship between PT and image quality or radiation dose was positive correlation. Conclu- sion PGA coronary CT angiography using 40ms padding time settings could offer assessable image quality at low HR and HRv.