门静脉狭窄对肝脏磁共振灌注成像影响的实验研究

目的探讨兔门静脉狭窄程度与肝脏磁共振(MR)灌注成像的关系.方法新西兰兔20只,静脉团注造影剂同时对肝门附近5个层面行MR动态扫描.扫描后1h依次用部分门静脉结扎法制作门静脉狭窄50%、75%模型,并且依次于狭窄后30min用同样方法行肝脏MR动态扫描.通过分析信号强度-时间(SI-T)曲线各参数,对兔肝脏MR灌注成像进行半定量分析.比较不同门静脉狭窄程度时曲线各参数的差别.结果除1只雌兔在50%狭窄扫描结束后死亡外,余19只兔均获得满意肝脏SI-T曲线.门静脉50%狭窄时与术前比较,相对肝动脉灌注指数(rHPI)、相对门静脉灌注指数(rPPI)、对比剂峰值时间(TTP)、最大线性斜率(SS)的差异均有统计学意义(均P＜0.05),而脾峰值增强前肝实质的增强峰值(PHa)和脾峰值增强后肝实质的增强峰值(PHp)的差异均无统计学意义(均P＞0.05).门静脉75%狭窄时与术前比较,rHPI、rPPI、TTP、SS、PHa、PHp的差异均有统计学意义(P＜0.01或0.05).门静脉75%狭窄时与50%狭窄时比较,rHPI、rPPI的差异均有统计学意义(均P＜0.01),而TTP、SS、Pha、PHp的差异均无统计学意义(均P＞0.05).随着门静脉狭窄程度的加重,TTP、PHa呈增加趋势(r=0.778、0.672,均P＜0.01),而SS、PHp呈减小趋势(r=-0.674、-0.530,P＜0.05或0.01),rHPI与rPPI与狭窄程度具有明显相关性(均r=0.956,均P＜0.01).结论随着门静脉狭窄程度加重,兔肝脏的门静脉灌注量降低,而肝动脉灌注量增加.肝脏MR灌注成像可提示门静脉狭窄程度.

The portal vein stenosis of the liver and its MR perfusion imaging in rabbits

Objective To investigate the relationship between magnetic resonance (MR) perfusion imaging of the liver and the extent of portal vein stenosis in rabbits. Methods The 50% and 75% portal vein stenosis was induced by partial portal vein ligation in 20 New Zealand rabbits. Thirty minutes later the dynamic contrast-enhanced MR imaging of the liver was performed. The parameters derived from dynamic contrast-enhanced MRI were calculated based on signal intensity-time (SI-T) curve; the relationship between enhancement parameters and the extents of portal vein stenosis was analysed. Results The satisfactory SI-T curves were acquired from the liver of all rabbits except one. When the extent of portal vein stenosis exceeded 50%,there were statistical differences in relative hepatic arterial perfusion index (rHPI),relative portal venous perfusion index (rPPI),time to peak (TTP) and steepest slope (SS) (P<0.05),but there were no differences in the peak height of the liver before the spleen enhanced (PHa) and peak height of the liver after the spleen enhanced (PHp). When the extent of portal vein stenosis exceeded 75%,there were statisticaly significant differences in rHPI,rPPI,TTP,SS,PHa and PHp (P<0.01). There were significant differences between 50% portal vein stenosis and 75% stenosis only in rHPI and rPPI. Significant correlations were observed between rHPI,rPPI and the extents of portal vein stenosis(r=0.956,P<0.01). Conclusions Increased the extents of portal vein stenosis in rabbits,portal perfusion decreased,arterial perfusion increased. MR perfusion imaging can reflect the extents of portal vein stenosis.