The Experimental And Clinical Study Of Liver Fibrosis With High-field MR Diffusion-weighted Imaging

Partâ… Diffusion-weighted MRI of the rat liver with modified sensitivity-encoding: initial experienceObjective:To evaluate prospectively the improvement in the image quality with the use of modified sensitivity-encoding(mSENSE) in diffusion-weighted imaging(DWI) of the rat liver and its effect on apparent diffusion coefficient(ADC) measurements.Materials and methods:Thirty rats underwent spin-echo echo-planar(SE-EPI) DWI of the liver with conventional phase encoding and with mSENSE,respectively.Five b values of 100,300,500,800 and 1000s/mm² were used.Image quality,signal-to-noise ratio(SNR) and ADC values of right posterior lobe were compared with different b values in both series.Matched-pairs Wilcoxon signed rank test,Friedman test and one-way analysis of variance(ANOVA) were used for statistical analysis.Results:The image quality scores and SNR decreased as the b value increased in both conventional DWI and mSENSE DWI groups.There were significant statistical differences(P＜0.05) among five different b values for image quality and SNR in the same group.Higher image quality scores and SNR values of the liver were obtained in mSENSE DWI group than those in conventional DWI group with the same b value and the differences were statistically significant(P＜0.05).The mean ADCs of liver in mSESNE DWI group were lower than those in conventional DWI group with the same b value,but there was no significant difference between the two sequences for hepatic ADC measurement(P＞0.05) at b values of 300,500,800 and 1000s/mm².Conclusion:mSENSE is useful in improving image quality and SNR of SE-EPI DWI of the rat liver without compromising ADC measurements.Partâ…¡Evaluation of liver fibrosis with diffusion-weighted MR imaging:a preliminary experimental studyObjective:To investigate the use of apparent diffusion coefficient(ADC) measurements based on diffusion-weighted MRI(DWI) for evaluating hepatic fibrosis.Materials and Methods:Diffusion-weighted MRI with modified sensitivity encoding(mSENSE) of liver were prospectively performed on sixty-three fibrotic rats induced by carbon tetrachloride(CCl₄) and on thirty normal rats using a single-shot spin-echo echo-planar sequence using five b values:100,300,500,800 and 1000s/mm².Rats were sacrificed immediately after MR scanning and the livers were resected for pathologic diagnosis.The fibrosis scores and inflammation grades were evaluated according to the Knodell histology activity index(HAI).Apparent diffusion coefficient(ADC) of the liver was measured respectively with five different b values. The ADC values in the liver parenchyma were compared among rats with different fibrosis scores and inflammation grades.Receiver operating characteristics analysis was used to assess the performance of ADC in prediction of the presence of score 1 or greater(fibrosis) and score 3 or greater hepatic fibrosis(severe fibrosis),and grade 2 or greater hepatic inflammation(moderate to marked inflammation).Results:Liver apparent diffusion coefficient decreased as the fibrosis score progressed.There was significant difference among different fibrosis scores for hepatic ADC at a b value of 800s/mm²(P=0.000).Hepatic ADC was a significant predictor of score 1 or greater and score 3 or greater fibrosis,respectively with areas under the curve of 0.827 and 0.913,sensitivity of 73.0%and 84.4%,and specificity of 83.3%and 83.3%(ADC with a b value of 800s/mm²,1.22-1.21×10^-3 mm²/s or less). There was a trend toward a decrease in hepatic ADC with increasing degree of inflammation.The best correlation was observed for a b values of 800s/mm² (r=-0.520,P=0.000).Hepatic ADC was a significant predictor of grade 2 or greater inflammation,with an area under the curve of 0.912,sensitivity of 80.9%and specificity of 87.0%(ADC with a b value of 800s/mm²,1.20×10^-3 mm²/s or less).Conclusion:Hepatic ADC measured with DWI can be used to quantify liver fibrosis and inflammation.It is potentially useful for early diagnosis of liver fibrosis and follow-up of patients after treatment.Partâ…¢Comparative study on clinical and pathological changes of liver fibrosis with diffusion-weighted imagingObjective:To evaluate the clinical practical value of apparent diffusion coefficient (ADC) measurements based on diffusion-weighted MR imaging(DWI) for quantification of liver fibrosis and inflammation for hepatitis viral infection.Materials and Methods:Diffusion-weighted MRI with parallel imaging was prospectively performed on eighty-five patients with chronic hepatitis and on twenty-two healthy volunteers within a single breath-hold using a single-shot spin-echo echo-planar sequence at b values of 100,300,500,800 and 1000s/mm². ADC values of the liver were measured respectively with five different b values.The inflammation grades and fibrosis stages were evaluated histologically by a biopsy sample.One-way analysis of variance(ANOVA) and Spearman's rank correlation test were used for statistical analysis.Receiver operating characteristics analysis was used to assess the performance of ADC in prediction of the presence of stage 2 or greater and stage 3 or greater hepatic fibrosis,and grade 1 or greater hepatic inflammation.Results:There was moderate negative correlation between hepatic ADCs and fibrosis stage.Hepatic ADCs decreased as the fibrosis stage progressed.With a b value of 800s/mm²,there was a significant decrease in hepatic ADC in patients with stage 3 or greater versus stage 2 or less fibrosis(P=0.000).Hepatic ADC was a significant predictor of stage 3 or greater fibrosis,with an area under the curve of 0.917, sensitivity of 80.0%and specificity of 91.5%for an ADC less than 1.19×10^-3mm²/s (b=800s/mm²).There was weak to moderate negative correlation between ADCs and inflammation grade.There was a trend toward a decrease in ADC with increasing degree of inflammation.Hepatic ADC was a significant predictor of grade 1 or greater inflammation,with an area under the curve of 0.781,sensitivity of 60.0%and specificity of 86.4%for an ADC less than 1.54×10^-3mm²/s(b=500s/mm²).Conclusion:There was negative correlation between ADCs and fibrosis stages or inflammation grades.Hepatic ADC measured with DWI can be used to quantify liver fibrosis and inflammation.DWI will be a new approach of the early stage diagnosis of fibrosis and follow-up for curative effect after treatment.