Study Of Microvascular Imaging In Hepatic Cirrhosis Based On Synchrotron Radiation X-ray Phase Contrast Computed Tomography

X-ray phase-contrast imaging?PCI?differs from the conventional X-ray absorption imaging technique,which utilizes phase shift information after X-ray passing through the specimens to image.Since the phase-contrast effect is 3 orders of magnitude higher than absorption,this technique has a superior image contrast in low-Z materials?e.g.,soft tissuses?without agent and can reveal the structures on the order of microns or even sub-microns.Combined with PCI and computed tomography?CT?,phase-contrast computed tomography?PCCT?could render the high resolution three-dimensional?3D?structures in the sample.In this work,the liver cirrhosis models induced via carbon tetrachloride?CCl₄?and bile duct ligation?BDL?in rats and human biliary cirrhosis?BC?tissues were used and imaged by PCCT.Then the qualitative and quantitative analyses of the anatomical changes of the microvasculature in cirrhosis were performed based on the 3D visualization.The main research contents are described as below:?1?CCl₄ and BDL induced rat cirrhosis models were imaged by PCCT to explore the imaging features of cirrhosis with different causes.Twenty-four Sprague-Dawley rats were randomly divided into four groups:CCl₄ control group,CCl₄ group,BDL sham operation group and BDL group.Portal pressure was measured before euthanasia.The livers from all animals were removed after euthanasia and were fixed in 10%neutral buffered formalin solution prior to imaging.After imaging,the samples were sliced and stained with Sirius red.The image features of cirrhosis were characterized using Murray's deviation,branch angle and micro-vessel density?MVD?.The degree of liver fibrosis was assessed by the fibrosis area.Correlations between the image features and portal pressure or fibrosis area were assessed.The results demonstrated that dilated and proliferative bile ducts in BDL models and disordered vessels in CCl₄ models were clearly showed via PCCT.The MD,branch angle and MVD were significantly increased in cirrhosis compared to the normal group.Significant correlations were observed between these indexes and portal pressure,as well as between these indexes and fibrosis area ratio in these two models.However,there was a difference of correlation between MD and fibrosis area ratio in the two models because of the different causes.This study indicates that MD,branch angle and MVD in cirrhosis may serve as new surrogate histopathological markers in evaluating cirrhosis or prognosing portal hypertension.?2?The human BC tissues were imaged by PCCT to explore the application of PCCT in human BC.Ten BC tissues were selected and rinsed with phosphoric acid buffer after operation,and then fixed in 10%neutral formalin solution for imaging.After imaging,these tissues were dehydrated,embedded into slices and stained.The results showed that the microvasculature in portal area was clearly visualized via PCCT without contrast agents.Based on 3D visualization technology,the tortuosity and elongation of bile ducts,and the folding of the wall of bile ducts were intuitively presented.The structures of the proliferative bile duct could be partly regarded as binary trees,yet a lot of ring connections were obsevered.The ruptures of portal vein and its abnormal structure were visible in CT and 3D images.Different types of blood vessels,including portal veins and hepatic veins,in addition to ductular proliferation and bile ducts,could be distinguished with good sensitivity,excellent specificity and excellent accuracy.Lumen areas of the vessels in PCCT images and the corresponding pathological sections were measured.There was a strong correlation between PCCT and histopathology.Results of Bland-Altman analysis demonstrated there is good agreement between the two methods.This study confirmed the potential application value of PCCT in the study of BC.