回顾性心电门控螺旋CT扫描模式下单扇区重建对图像质量的改善作用

Single cycle reconstruction technique improves image quality with retrospectively electrocardiogram-gated spiral acquisition mode

目的探讨256层螺旋CT在采用回顾性心电门控螺旋扫描模式进行冠状动脉成像中发生非预期自由呼吸时,单扇区重建算法改善图像质量的应用价值。方法将2017年6月10日至7月10日采用回顾性心电门控螺旋扫描进行冠状动脉CT血管造影成像,且CT横断面图像在肺窗上观察存在运动伪影的24例患者纳入本研究。对CT原始数据进行单扇区重建(单扇区重建组)与多扇区重建(多扇区重建组),两组重建算法选取相同时相进行数据分析,比较两组图像的平均CT值、图像噪声、信噪比、对比噪声比。采用独立样本t检验比较图像客观指标的差异,采用χ~2检验比较图像主观指标的差异。结果共分析患者冠状动脉的350个节段,采用单扇区重建算法,冠状动脉节段图像质量的可诊断率为98.3%(344/350),高于多扇区重建算法的84.0%(294/350),差异有统计学意义(χ~2=44.241,P<0.05)。单扇区重建组的图像噪声高于多扇区重建组[(51.3±9.8)HU vs(40.7±6.0)HU,t=-4.647,P<0.05]。两种重建方法信噪比的差异无统计学意义(t=0.941,P=0.351)。两组对比噪声比在升主动脉根部、左冠状动脉主干和右冠状动脉初段、中段、末段差异均无统计学意义(t=1.039、0.610、0.571、0.438、0.396,P=0.304、0.548、0.574、0.666、0.696)。结论采用回顾性心电门控螺旋扫描模式进行冠状动脉CT血管造影成像时,应用单扇区重建算法可以减少图像因患者屏气不佳或心脏波动产生的运动伪影,提高医师的诊断信心。

Objective To explore the application value of the single cycle reconstruction algorithm in improving image quality of free-breathing 256-slice row coronary computed tomography angiography（CCTA） with retrospectively electrocardiogramgated spiral acquisition mode. Methods Twenty-four patients whose CCTA images had motion artifact were recruited in this study between Jun.10 and Jul. 10, 2017. CCTA was examined with the retrospectively electrocardiogram-gated spiral scanning mode. All images were reconstructed using single cycle reconstruction（single cycle group） and multi-cycle reconstruction（multi-cycle group） methods. The two reconstruction algorithms used same phase for analyzing data. The mean CT value, image noise, signalto-noise ratio（SNR） and contrast-to-noise ratio（CNR） were compared between the two groups. T test was performed to analyze the objective indicators, and χ^2=test was performed to analyze the subjective indicators. Results Totally 350 segments of coronary were evaluated in this study. Diagnosis rate of coronary segment image quality with single cycle reconstruction was 98.3%（344/350）, which was significantly higher versus 84.0%（294/350） with multi-cycle reconstruction（χ^2=44.241, P〈0.05）. The image noise was significantly higher in the single cycle group than that in the multi-cycle group（[51.3±9.8] HU vs [40.7±6.0] HU, t=-4.647, P〈0.05）. There was no significant difference in SNR between the two reconstruction algorithms（t=0.941, P=0.351）. The CNRs were not significantly different in the ascending aortic root, left main coronary or proximal, middle, and distal right coronary between the two reconstructive algorithms（t=1.039, 0.610, 0.571, 0.438, and 0.396; P=0.304, 0.548, 0.574, 0.666, and 0.696）. Conclusion Single cycle reconstruction technique can reduce motion artifact caused by unanticipated free-breathing or heart fluctuations in CCTA under the retrospectively electrocardiogram-gated spiral scanning mode and increase diagnosis confidence of doctors.