固定扫描延时对肝脏CT门脉期增强的影响

Effect of fixed scan delay on liver CT at hepatic portal venous phase

目的分析上腹部CT增强检查中动脉期-门脉期固定延时对门脉期增强的影响。方法 87例上腹部CT增强检查,采用团注追踪技术(BTT)触发扫描动脉期,延迟30s行门脉期扫描。比较动脉期序列图像中肝顶、肝门和肝底三个层面的主动脉CT值的大小关系分析血液循环速度的快慢,据此把所有样本按顺序排列并均分为三组,比较门脉期肝实质增强和门脉增强。结果组间性别组成、年龄、身高和体重的比较均无显著性差异(P> 0. 05);第二组的门脉期肝实质增强(54±16) HU显著高于第一组的(43±15) HU(P=0. 016),略高于第三组的(49±11) HU;第二组的门脉期门脉增强(59±22) HU略高于第一组的(54±26) HU和第三组的(52±22) HU。结论固定延时导致门脉期增强一致性下降。基于BTT的主动脉CT值随时间的变化规律可能与血液循环速度的个体差异有关,可用于优化门脉期延迟时间设置。

Objective To investigate the effect a fixed scan delay from Hepatic arterial phase （HAP） to hepatic portal venous phase （PVP） on the latter in multi-phase abdominal CT. Methods Eighty seven patients who underwent abdominal CT with same scanning protocol were included retrospectively. HAP was timed by bolus tracking technique （BTT） with triggering threshold set at 120 HU of aortic CT value, followed by PVP with a fixed delay of 30 s. The patients were divided equally into three groups based on blood circulation speeds deduced by comparing aortic CT values of the top, portal and bottom slice of HAP image sequences. The hepatic enhancement and the portal-to-hepatic contrast of PVP images were compared between groups. Results There were no significant differences between the three groups in terms of sex distribution, age, height and weight （ P 〉0.05）. In PVP, the hepatic enhancement of the three groups was （43±15） HU, （54±16） HU and （49±11） HU respectively, among which significant difference was observed between group 2 and group 3 （ P =0.016）; the portal-to-hepatic contrast was （54±26） HU, （59±22） HU and （52±22） HU respectively, among which the mean value of group 2 was greater slightly than that of the other two. Conclusion Fixed scan delay degrades the consistency of contrast enhancement at PVP. The individual difference of blood circulation speed, extracted from aortic contrast variation based on BTT is potential to be used to improve the timing of PVP.