Background: In contrast to classical pulsed gradient diffusion-weighted MRI, oscillating gradient diffusion-weighted MR imaging (DWI) is sensitive to short distance diffusion changes at the intracellular level.

Purpose: To compare the diagnostic performance of pulsed and oscillating DWI for characterizing hepatocellular nodules in a rat model of hepatic cirrhosis.

Study type: Prospective, experimental study.

Animal model: Cirrhosis was induced by weekly intraperitoneal injection of diethylnitrosamine in Wistar rats.

Field strength/sequence: Ex vivo liver MRI was performed at 7T with T1 -weighted, T2 -weighted, pulsed, and oscillating gradient diffusion-weighted sequences.

Assessment: Apparent diffusion coefficient from pulsed (ADCpulsed ) and oscillating gradient (ADCoscillating ) sequences was calculated in 82 nodules identified on the T1 /T2 -weighted images and on pathological examination. Two pathologists classified the nodules in three categories: benign (regenerative and low-grade dysplastic nodules), with intermediate malignancy (high-grade dysplastic nodules and early hepatocellular carcinomas) and overtly malignant (progressed hepatocellular carcinomas).

Statistical tests: Differences between groups were assessed with Kruskal-Wallis and Mann-Whitney tests.

Results: ADC, mainly ADCoscillating , increased in the group of nodules with intermediate malignancy (ADCpulsed : 0.75 ± 0.25 × 10-3 mm2 /s vs. 0.64 ± 0.07 × 10-3 mm2 /s in benign nodules, P = 0.025; ADCoscillating : 0.81 ± 0.20 × 10-3 mm2 /s vs. 0.65 ± 0.13 × 10-3 mm2 /s, P = 0.0008) and ADCpulsed decreased in the group of progressed hepatocellular carcinomas (ADCpulsed : 0.60 ± 0.08 × 10-3 mm2 /s, P = 0.042; ADCoscillating : 0.68 ± 0.08 × 10-3 mm2 /s, P = 0.1).

Data conclusion: ADC during hepatocarcinogenesis in rats increased in nodules with intermediate malignancy and decreased in progressed hepatocellular carcinomas. Our results suggest that oscillating gradient DWI is more sensitive to the early steps of hepatocarcinogenesis and might be useful for differentiating between high-grade dysplastic nodules / early hepatocellular carcinomas and regenerating nodules / low-grade dysplastic nodules.