The Role of Diffusion Weighted Magnetic Resonance Imaging in the Differential Diagnosis of Hepatocellular Carcinomas and Regenerative-Dysplastic Nodules in Cirrhotic Liver

Objective: The differential diagnosis of hepatocellular carcinomas (HCC) and regenerative-dysplastic nodules (RDN) in cirrhotic patients is critical for patient management and can be a challenging imaging procedure. The goal of our study is to evaluate the contribution of diffusion-weighted imaging in the differential diagnosis of these lesions.

Materials and Methods: 50 patients, diagnosed as hepatocellular carcinoma and/or RDN in cirrhotic liver, were included in our study. All HCC and some of RDN lesions (5 lesions out of 25) were confirmed histopathologically. Rest RDN was called with imaging characteristics and follow-up images (18-27 months, mean 19.2 months follow up time). Magnetic resonance images along with Diffusion weighted images with b = 800 s/mm2 were evaluated by 2 radiologists. All imaging examinations were performed with 1.5 Tesla MR machine. Diffusion weighted images and ADC (apparent diffusion coefficient) mapping of lesions were evaluated and ADC values were calculated. The results were compared with conventional dynamic magnetic resonance images.

Results: In our study 95% of 40 Hepatocellular carcinomas demonstrated diffusion restriction. 52% of 25 RDN were isointense on diffusion-weighted images. The difference of the signal intensity distribution was statistically significant between two lesions (p<0.001). On quantitative analysis, we calculated ADC values of lesions and ADC ratio of lesion-to-liver values. The mean ADC values and ADC ratio of the RDN was higher than that of the hepatocellular carcinomas, and there was a significant difference between 2 groups (p<0.001). When a cutoff value of 0.95 is considered for ADC ratio, on diffusion imaging with ADC mapping 97.5% sensitivity and 64% specificity can be calculated to differentiate hepatocellular carcinoma from RDN.

Conclusion: Diffusion weighted imaging can improve differential diagnosis of these two lesions in cirrhotic liver combined with contrast enhanced magnetic resonance imaging.