Comparison of imaging features between focal nodular hyperplasia and hepatocellular carcinoma on MR diffusion weighted imaging

Objective: To investigate the imaging features of focal nodular hyperplasia and hepatocellular carcinoma on DWI. Methods: The data of patients with histopathologically confirmed FNHs and HCCs between August 2008 and November 2010 were collected. A total of 24 patients with 26 FNH lesions and 36 patients with 39 HCC lesions were included in our study. All patients underwent breath-hold DWI with b = 500 s/mm2 and dynamic contrasted-enhanced (DCE) MRI. The imaging findings of FNHs and HCCs were retrospectively analyzed and compared. The signal intensity (SI) of the lesions on DWI were classified as iso-, slightly high, high SI and the distribution of SI between FNHs and HCCs was compared with Fisher exact test. ADC value and lesion-to-liver ADC ratio of FNHs and HCCs were measure and compared by using independent sample t test. ROC was performed to assess the diagnostic value of ADC value and lesion-liver ADC ratio in the characterization FNHs versus HCCs. Results: Of 26 FNHs, 23 manifested as isointensity or slightly high SI on DWI, but most 25 out of 39 HCCs showed high SI. The distribution of SI between FNHs and HCCs had significant difference (P=0.000). The mean ADC value and lesion-liver ADC ratio for FNHs [(1.76±0.62) × 10-3 mm2/s and 1.06±0.18, respectively] were significantly higher (P=0.001, P=0.000, respectively) than those for HCCs [(1.26±0.46) × 10-3 mm2/s and 0.79±0.12, respectively]. The area (Az) under the ROC for the ADC value and lesion- liver ADC ratio for the differentiation of FNHs versus HCCs were 0.79±0.05 and 0.85±0.05, respectively, with no significant difference (P=0.270). The specificity of the two measures was 69.23% and 97.44%, respectively, with significant difference (P=0.001). Conclusion: FNH shows isointensity or slightly high SI with relatively higher ADC value and lesion-liver ADC ratio than those of HCCs on DWI, which is characteristic for its diagnosis and differentiation. (authors)