320排CT可变螺距采集技术在经导管主动脉瓣置换术术前评估中的应用

Application of 320-row CT variable helical pitch technique in preoperative evaluation of transcatherter aortic valve replacement

目的:探讨CT可变螺距(VHP)采集技术在大范围主动脉及主动脉瓣膜成像中的应用价值。方法:回顾性分析我院2016年1月至2018年4月经导管主动脉瓣置换术(TAVR)术前扫描CTA患者54例(实验组),采用东芝320排CT,扫描范围从胸廓入口扫描至股骨中段水平;胸廓入口至心底采用小螺距心电门控,心底至股骨中段水平采用大螺距非心电门控扫描模式;管电压120 kV,智能管电流,层厚/间距0.5/0.3 mm,对比剂90~100 mL,流速4~5 mL/s;分别重建30%、40%、75%时相。对照组32例患者采用大范围全门控扫描方案,扫描范围、扫描条件、重建参数、对比剂用量均与实验组相同。结果:53例屏气好的患者扫描均获得了成功,1例患者因屏气能力太差导致扫描失败。回顾性心电门控可以很好地获得主动脉瓣瓣膜的图像,并可以观察冠状动脉狭窄情况;大范围非心电门控扫描可获得所有的外周血管入路。结论:VHP技术适用于TAVR术前评估,一次扫描可完成大范围全主动脉的扫描,对比剂使用少,且可观察瓣膜及冠状动脉;缺点是屏气要求高,心电门控时只能采用全门控,辐射剂量较高。

Objective: To explore the value of 320-row CT variable helical pitch(VHP) technique applied in preoperative evaluation of transcatherter aortic valve replacement(TAVR). Methods: From Jan. 2016 to Apr. 2018, 320-row CT angiography was performed in 54 patients before TAVR, and the data were analyzed retrospectively. CT scanning range is from thorax entrance to the level of the middle segment of the femur. Short-pith spiral electrocardiography(ECG)-gated scanning was utilized to examine the level from thorax entrance to the heart bottom, while high-pith spiral non-ECG-gated scanning was used for the level from heart bottom to middle segment of the femur. Scanning parameters were shown as follows: 120 kV tube voltage, auto tube current, 0.5 mm/0.3 mm thickness/spacing, 90-100 mL contrast, and 4~5 mL/s flow rate. The reconstructed phases were 30%, 40%, and 75%, respectively. The control group of 32 patients underwent a large-scale full-gated scanning. The scanning range, scanning conditions, reconstruction parameters and contrast agent dosage were the same as those of the experimental group. Results: CT scanning was performed successfully in 53 patients who could hold their breath. However, one case failed because of the breath. High quality image of aortic valve and coronary diagnostic information could be observed. Large-range non-ECG-gated scanning could show all the entrances of peripheral blood vessels. Conclusions: The VHP technique is feasible for preoperative evaluation of TAVR and aortic valve, and enables large range CT scanning of the entire aorta with less contrast. However, the disadvantage is that VHP technique needs to hold breath when using ECG-gated scanning with higher radiation dose.