Phase-contrast computed tomography: A correlation study between portal pressure and three dimensional microvasculature of ex vivo liver samples from carbon tetrachloride-induced liver fibrosis in rats

Objective: Microvascular changes in liver fibrosis are considered as an important pathophysiological characteristic. Now, there is a lack of high-resolution three-dimensional (3D) imaging methods for observing the microvasculature throughout the entire livers. This study aims to investigate the 3D microvascular changes in the whole fibrotic livers via X-ray phase-contrast computed tomography (PCCT) and explore the correlations between portal pressures and microvascular changes in liver fibrosis progression. Methods: Twenty-three fibrotic rats were imaged ex vivo using PCCT. Morphological changes of the microvasculature were characterized using tortuosity, texture features of the vascular inner wall, fractal dimension (FD) and Murray's deviation (MD), and quantitative changes were evaluated by microvascular density (MVD). The degree of liver fibrosis was assessed by histochemistry, and the portal pressure of each rat was measured before euthanasia. Results: Using PCCT, subtle vascular structures in fibrotic livers were revealed in the 3D modality, and the qualitative description and quantitative evaluation of microvascular changes showed important differences during the progression of liver fibrosis. Moreover, microvascular changes, including tortuosity, texture features of the vascular inner wall, MD and MVD, exhibited good correlations with the fibrosis area (R >= 0.729, P < 0.001) and portal pressure (R >= 0.715, P < 0.001) in the development of fibrosis. Conclusions: PCCT technique demonstrates outstanding potential for 3D visualization of microvasculature in liver fibrosis. Microvascular changes in fibrotic livers may serve as a new surrogate histopathological marker in evaluating portal pressures or prognosing portal hypertension.