降低门静脉灌注量对肝脏MR ADC值的影响

Impact of portal vein perfusion decrease on MR ADC value of the liver

目的探讨不同b值下门静脉灌注量降低对肝脏ADC值的影响。方法对25名健康志愿者分别在静息状态和标准运动后(有效减少门静脉灌注量)采用相位对比法定量测量门静脉灌注量,比较b值不断递增时(b为0、250、500、750、1000s/mm2)门静脉灌注量降低对肝右前叶、右后叶ADC值的影响。结果门静脉灌注量在运动后均显著下降,平均下降比例为43.31%。b=500、750、1000s/mm2时,肝右后、右前叶运动前、后ADC值的改变均无统计学意义;b=250s/mm2时,肝右后、右前叶ADC值的改变均有统计学意义,此时门静脉灌注量的改变量与肝右后、右前叶ADC值的变化量无确切相关性(r=0.16,P=0.45;r=0.16,P=0.46)。结论选择较大b值(b≥500s/mm2)可有效减小门静脉灌注量对肝脏ADC值的影响,以获得稳定、优化的ADC值。

Objective To assess whether hepatic ADC value are influenced by hepatic perfusion decrease under different b values. Methods Totally 25 healthy volunteers underwent DWI before and after a standard exercise （an effective method to decrease portal vein flow）. Phase contrast technique was used to detect the perfusion of portal vein, and breath-hold technique was taken for DWI at b-values of 0, 250, 500 and 750 and 1000 s/mm2. Then hepatic ADC values of posterior and anterior right lobe were measured and compared at different states. Results After exercise, portal blood flow decreased significantly in all volunteers, with the mean rate of 43.31%. The ADC values of posterior and anterior right lobes in b= 500, 750, 1000 s/mm2 before and after exercise had no statistical significance, while statistical significance was found when b=250 s/mm2. The decrease of portal vein flow had no relationship with ADC values of posterior and anterior right lobes when b= 250 s/mm2 （r= 0.16, P=0.45; r= 0.16, P=0.46）. Conclusion With regard to the measurements of ADC, the effect of perfusion can he minimized with higher b values （b≥500 s/mm2 ） in order to obtain stable and optimized ADC value.