Relationship Of Magnetic Resonance Diffusion-weighted Imaging To Histology In Chronic Viral Hepatitis

Objective:Chronic viral hepatitis and consequent liver cirrhosis are severe andcommon disease in China. Early evaluation of disease activity and degree ofliver fibrosis is very important for the treatment of hepatitis and prevention ofits progress. Diffusion-weighted imaging (DWI) as a new technique ofmagnetic resonance imaging (MRI) is the only method of performing in vivomeasurement of molecular diffusion movement noninvasively. The purposeof this study was to investigate the correlation between DWI and thehistological severity of chronic viral hepatitis by using a 3.0T MRI scanner.Methods:Routine MRI scan and DWI study was performed for 49 patients withchronic viral hepatitis and 10 healthy volunteers on 3.0T magnet. Theapparent diffusion coefficient (ADCs) in the liver parenchyma of each lobewere measured using DWI on ADC maps with 5 increasing b-values from100, 200, 400, 600, to 800 sec/mm², respectively. The 49 patients underwent liver biopsy after MRI scan within 7 days. Biopsy specimens were scoredfor fibrosis and necroinflammation according to the Knodell histologyactivity index (HAI). Based on the necroinflammation score, the 35 patientswere divided into 4 grades: G₁ (slight hepatitis, 19 patients), G₂ (mildhepatitis, 14 patients), G₃ (moderate hepatitis, 11 patients) and G₄ (severehepatitis, 5 patients). According to the fibrosis score, the patients weredivided into 4 stages: So (no fibrosis, 13 patients), S₁ (piecemeal fibrosis, 21patients), S₃ (bridging fibrosis, 5 patients) and S₄ (cirrhosis, 10 patients). TheADCs were compared with the HAI scores.Results:Because statistical differences of ADCs were found among the four liverlobes, therefore, the anterior right lobe was chosen according to the site ofliver biopsy. A significant difference in ADCs was found comparing patientswith fibrosis (S₁, S₃, S₄) to patients without fibrosis (S₀) and the controls withthe b=400, 600, 800sec/mm². The ADC decreased as the necroinflammationand fibrosis score increased, and the correlation was statistically significantwith the b=400, 600, 800sec/mm². When the b value was selected at800sec/mm², ADCs was most significantly correlated negatively with theactivity grades and fibrosis stages. The correlation factor of ADCs to thegrades was 0.470, and 0.659 to the stages, higher than clinical and laboratoryserum biomarkers, such as ALT, AST, AST/ALT, ALB, A/G and Child-Pughstages, also higher than the morphological changes revealed by imaging, suchas unevenness of hepatic parenchyma, adenopathy, ascites, etc. When thecutoff points between G₁/G₂, G₂/G₃ and G₃/G₄ were set as ADCs=0.00131,0.00131 and 0.00123, and those of S₀/S₁, S₁/S₃, S₃/S₄ were set as ADCs=0.00127, 0.00126 and 0.00125, a sensitivity of 55.6～100%, and aspecificity of 72.7～100% were respetively achieved.Conclusion:ADCs measured by liver diffusion-weighted MRI are correlated with theactivity of necroinflammation and the degree of fibrosis in chronic viralhepatitis, especially when b=800 sec/mm². MR DWI might be a potentialnoninvasive in vivo method to assess the disease activity of chronic viaralhepatitis.