双源CT双能量肺灌注成像对比剂应用参数优化及辐射剂量的研究

Dual energy CT lung perfusion imaging using dual source CT:optimization of contrast medium use and radiation dose

目的：评价对比剂注射速率、扫描方向和对比剂用量对双源CT（DSCT）双能量肺灌注成像质量的影响，优选最佳对比剂注射参数。材料与方法：2008年5～8月共79例患者参加了本研究。将患者分为6组：第1～3组，对比剂浓度300mgI／ml、用量1．5ml／kg、头足方向、注射速率分别为3、4、5ml／s；第4、5组，对比剂浓度300mgI／ml、足头方向，注射速率4ml／s、用量分别为1．5、1．0ml／kg；第6组，对比剂浓度350mgI／ml、足头方向，注射速率5ml／s、用量1．2ml／kg。测量升主动脉、肺动脉主干以及上腔静脉的CT值、计数肺动脉显示级别并定量评价DSCT双能量肺灌注成像的影像质量。统计学分析应用SPSS11．5软件进行。结果：组4和组6增强方案肺动脉强化值最高而上腔静脉强化值最低，同时有优良的双能量肺灌注和肺动脉图像质量。2名观察者分析双能量肺灌注图像质量的一致性好（Kappa值=0．619，P=0．000）。双能量肺灌注图像质量和肺动脉强化值之间有弱的正相关关系。双能量模式扫描的辐射剂量较常规单源模式降低了5．0％和12．4％。结论：组4和组6的增强方案可获得满意的肺双能量灌注成像的图像质量，结合临床实用情况，建议采用组4的增强方案。肺双能量扫描降低了患者接受的辐射剂量。

Objective： To evaluate the effect of injection rate, volume, and scanning direction on image quality of dual energy lung perfusion imaging using dual source CT （DSCT）. Materials and Methods： Seventy-nine patients underwent DSCT examination from May to Aug. 2008. All patients were divided into six groups： group 1 to 3, contrast medium 300mgI/ml, dosage 1.5ml/kg, cranial to caudal direction, injection rate of 3, 4, 5ml/s： group 4, 5, contrast medium 300mgI/ml, dosage 1.5ml/kg, caudal to cranial direction, injection rate of 4ml/s, dosage 1.0 and 1.5ml/kg; group 6, contrast 350mgI/ml, scanning from caudal to cranial, dosage 1.2ml/kg, injection rate of 5ml/s. CT number on ascending aorta, pulmonary trunk, and superior vena cava were measured. Visualization scale of pulmonary artery and image quality dual energy lung perfusion imaging were recorded. Statistical analysis was performed using the software of SPSS 11.5 version. Results： Maximal pulmonary trunk en- hancement and lowest superior vena cava enhancement were found in group 4 and group 6 with good image quality of dual energy lung perfusion imaging and pulmonary artery. Good interobserver agreement was found for dual energy lung perfusion imaging（Kappa value=0.619, P=0.000）. Image quality of dual energy lung perfusion imaging correlated positively with pulmonary trunk enhancement. Radiation dose was decreased by 5.0% and 12.4% for dual energy mode, compared with conventional CT scan mode. Conclusions： Scanning protocols of group 4 and group 6 can provide better image quality of lung dual energy perfusion imaging; however, the parameters of group 4 are recommended for clinical routine use. Dual energy lung perfusion imaging has lower radiation dose than routine single source lung scan.