双源CT冠状动脉成像的图像质量及重组时相与心率的关系

The impact of heart rate on image quality and reconstruction timing of dual-source CT coronary angiography

目的探讨双源CT冠状动脉成像的图像质量和重组时相与心率的关系。方法对95例临床可疑冠心病患者进行双源CT增强扫描，检查前均不使用β受体阻滞剂控制心率。按扫描时心率分为3组：低心率组（≤70次／min）26例，中心率组（71～90次／min）37例，高心率组（≥91次／min）32例。利用回顾性心电门控重建出10％～100％R-R时相的图像，分析不同R．R时相冠状动脉的图像质量情况及其与心率的关系。结果低、中、高心率3组图像质量评分分别为（1．08±0．27）、（1．32±0．58）、（1．47±0．61）分，低心率和中心率组图像质量评分差异无统计学意义（P〉0．05），低心率组图像质量评分显著优于高心率组（P〈0．05），中心率组和高心率组图像质量评分差异无统计学意义（P〉0．05）。只有1．4％（19／1386）的冠状动脉节段不可评价。74例患者（77．9％）可在单一重组时相获得冠状动脉各段最佳图像质量。低心率组23例（88．5％）最佳重组时相在舒张中晚期；高心率组27例（84．4％）的最佳重组时相前移至舒张早期和收缩末期。结论双源CT能够在相当宽的心率范围内提供优良的图像质量；多数患者可在单一时相获得各支冠状动脉最佳质量图像，随着心率的增快最佳重组时相从舒张中晚期前移至舒张早期和收缩末期。

Objective To evaluate the impact of patient＇s heart rate （HR） on coronary CT angiography （CTA） image quality （IQ） and reconstruction timing in dual-source CT （DSCT）. Methods Ninety-five patients with suspicion of coronary artery disease were examined with a DSCT scanner （ Somatom Definition, Siemens） using 32 × 0. 6 mm collimation. All patients were divided three groups according to the heart rate （HR）： group 1, HR≤70 beats per minute （bpm）, n =26; group 2, HR 〉70 bpm to ≤90 bpm, n=37; group 3, HR 〉90 bpm, n =32. No beta-blockers were taken before CT scan. 50- 60 ml of nonionic contrast agent were injected with a rate of 5 ml/s. Images were reconstructed from 10% to 100% of the R-R interval using single-segment reconstruction. Two readers independently assessed IQ of all coronary segments using a 3-point scale from excellent （ 1 ） to non-assessable （3） for coronary segments and the relationship between IQ and the HR. Results Overall mean IQ score was 1.31±0. 55 for all patients with 1. 08 ±0. 27 for group 1, 1.32 ±0. 58 for group 2 and 1.47 ±0. 61 for group 3. The IQ was better in the LAD than the RCA and LCX （ P 〈 0. 01 ）. Only 1.4% （19/1386） of coronary artery segments were considered non-assessable due to the motion artifacts. Optimal image quality of all coronary segments in 74 patients （77. 9% ） can be achieved with one reconstruction data set. The best IQ was predominately in diastole （88. 5% ） in group 1, while the best IQ was in systole （84. 4% ） in group 3. Conclusions DSCT can achieve the optimal IQ with a wide range of HR using single-segment reconstruction. With the increasing of HR, the timing of data reconstruction for the best IQ shifts from mid-diastole to systole.