Liver fibrosis: An intravoxel incoherent motion (IVIM) study

Abstract

Purpose: 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. Materials and Methods:Liver fibrosis was induced in male adult C57BL/6N mice (22-25 g; n ¼ 12) by repetitive dosing of carbon tetrachloride (CCl 4 ). The respiratorygated 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 hematoxylineosin and Masson's trichrome staining.Results: 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.Conclusion: 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.

Evaluation of fibrosis and inflammation in diffuse liver diseases using intravoxel incoherent motion diffusion-weighted MR imaging

“…Categorical variables were evaluated by v 2 and Fisher's exact test. For statistical analysis, necro-inflammatory activity score was grouped as none (score 0), mild (scores 1-6), moderate (scores 7-12), and severe inflammation (scores [13][14][15][16][17][18]. The Ishak fibrosis staging was categorized into none (F0), mild to moderate fibrosis (F1-F3), and marked fibrosis/cirrhosis (F4-F6).…”

“…The IVIM model allows separating the liver signal intensity changes due to true molecular diffusion from those related to perfusion within the tissue. Recently, it has been proposed that the IVIM model, and particularly the perfusion-related parameters D* and f, would be more advantageous to evaluate liver fibrosis than conventional ADC measurements [5,[13][14][15][16][17][18][33][34][35]. However, the influence of liver inflammation, steatosis and siderosis on liver values has to be considered in this analysis.…”

“…The bi-exponential intravoxel incoherent motion (IVIM) DW model [11,12] allows separating the diffusion and perfusion effects by quantifying the pure diffusion coefficient (D), the pseudo-diffusion (D*), and vascular fraction (f) microperfusion parameters. Lower ADC values in liver with fibrosis were associated to both liver compartment restrictions [13][14][15][16]. Other authors found lower ADC values in fibrotic livers being only dependent on perfusion parameters changes [5,17,18].…”

Liver intravoxel incoherent motion (IVIM) magnetic resonance imaging: a comprehensive review of published data on normal values and applications for fibrosis and tumor evaluation

“…In a rat model of diethylnitrosamineinduced liver fibrosis, Zhang et al (57) reported that PF values decreased significantly with the increasing fibrosis level; but Dslow was poorly correlated with fibrosis level. In a carbon tetrachloride induced rat liver fibrosis model, Chow et al (58) reported that as liver fibrosis progressed, Dslow and Dfast decreased, however there was no change in PF. Joo et al (59) reported that PF was significantly lower in rabbits with nonalcoholic fatty liver disease than in those significantly lower in fibrotic livers.…”

Intravoxel incoherent motion: application in differentiation of hepatocellular carcinoma and focal nodular hyperplasia

“…Both diffusion and perfusion can be quantified or estimated separately by multi-b values according to a bi-exponential model, including D, f, and D*, which represent the pure diffusion coefficient, perfusion fraction, and pseudodiffusion coefficient, respectively. Recently, IVIM has become popular and has been applied routinely in the human body, mostly to evaluate therapeutic response (5,6), in chronic disease assessment (7,8), and for lesion detection and characterization (9,10). One of the most conspicuous advantages of IVIM is that it does not require contrast medium injection.…”