Laboratory of Biomedical Imaging and Signal Processing, University of Hong Kong, Pokfulam, Hong Kong SAR, China.
J Magn Reson Imaging. 2012 Jul;36(1):159-67. doi: 10.1002/jmri.23607. Epub 2012 Feb 14.
To characterize longitudinal changes in molecular water diffusion, blood microcirculation, and their contributions to the apparent diffusion changes using intravoxel incoherent motion (IVIM) analysis in an experimental mouse model of liver fibrosis.
Liver fibrosis was induced in male adult C57BL/6N mice (22-25 g; n = 12) by repetitive dosing of carbon tetrachloride (CCl(4) ). The respiratory-gated diffusion-weighted (DW) images were acquired using single-shot spin-echo EPI (SE-EPI) with 8 b-values and single diffusion gradient direction. True diffusion coefficient (D(true) ), blood pseudodiffusion coefficient (D(pseudo) ), and perfusion fraction (P(fraction) ) were measured. Diffusion tensor imaging (DTI) was also performed for comparison. Histology was performed with hematoxylin-eosin and Masson's trichrome staining.
A significant decrease in D(true) was found at 2 weeks and 4 weeks following CCl(4) insult, as compared with that before insult. Similarly, D(pseudo) values before injury was significantly higher than those at 2 weeks and 4 weeks after CCl(4) insult. Meanwhile, P(fraction) values showed no significant differences over different timepoints. For DTI, significant decrease in ADC was observed following CCl(4) administration. Fractional anisotropy at 2 weeks after CCl(4) insult was significantly lower than that before insult, and subsequently normalized at 4 weeks after the insult. Liver histology showed collagen deposition, the presence of intracellular fat vacuoles, and cell necrosis/apoptosis in livers with CCl(4) insult.
Both molecular water diffusion and blood microcirculation contribute to the alteration in apparent diffusion changes in liver fibrosis. Reduction in D(true) and D(pseudo) values resulted from diffusion and perfusion changes, respectively, during the progression of liver fibrosis. IVIM analysis may serve as valuable and robust tool in detecting and characterizing liver fibrosis at early stages, monitoring its progression in a noninvasive manner.
利用体素内不相干运动（IVIM）分析，在肝纤维化的实验性小鼠模型中，描述分子水扩散、血液微循环及其对表观扩散变化的贡献的纵向变化。
雄性成年 C57BL/6N 小鼠（22-25g；n=12）通过重复给予四氯化碳（CCl(4)）诱导肝纤维化。使用单次激发自旋回波 EPI（SE-EPI）采集呼吸门控扩散加权（DW）图像，共 8 个 b 值和单个扩散梯度方向。测量真实扩散系数（D(true)）、血液假性扩散系数（D(pseudo)）和灌注分数（P(fraction)）。也进行扩散张量成像（DTI）进行比较。用苏木精-伊红和 Masson 三色染色进行组织学检查。
与损伤前相比，在 CCl(4)损伤后 2 周和 4 周，发现 D(true)显著降低。同样，损伤前的 D(pseudo)值明显高于 CCl(4)损伤后 2 周和 4 周的值。同时，不同时间点的 P(fraction)值没有显著差异。对于 DTI，在给予 CCl(4)后观察到 ADC 显著降低。CCl(4)损伤后 2 周的各向异性分数明显低于损伤前，随后在损伤后 4 周恢复正常。肝组织学显示，CCl(4)损伤的肝脏有胶原沉积、细胞内脂肪空泡和细胞坏死/凋亡。
分子水扩散和血液微循环均导致肝纤维化时表观扩散变化的改变。在肝纤维化进展过程中，D(true)和 D(pseudo)值的降低分别归因于扩散和灌注的变化。IVIM 分析可能成为检测和特征化早期肝纤维化以及非侵入性监测其进展的有价值和强大工具。
