High-b-value diffusion-weighted MR imaging of hepatocellular lesions: estimation of grade of malignancy of hepatocellular carcinoma.

Purpose: To evaluate the effectiveness of diffusion-weighted magnetic resonance imaging (DWI) in estimating the grade of malignancy of hepatocellular carcinoma.

Materials And Methods: Dynamic contrast-enhanced computed tomography (CE-CT) and DWI (b value, 1000 s/mm(2)) were performed on 73 patients. Using DW images, the lesions were classified as "visible" or "invisible." The apparent diffusion coefficient (ADC) of the lesions was measured. Furthermore, the lesions were classified as hypervascular or iso-hypovascular using arterial phase CE-CT images. The image findings for each lesion type were compared.

Results: The 73 patients had 98 hepatocellular lesions, of which 12 were histologically diagnosed as dysplastic nodules; 39, well-differentiated HCCs; 33, moderately differentiated HCCs; and 14, poorly differentiated HCCs. The mean ADC values of moderately poorly-differentiated HCCs were significantly lower than well-differentiated HCCs and dysplastic nodules (P < 0.01). On DW images, >90% of moderately (30/33) and poorly differentiated HCCs (13/14) were visible, while 51% of well-differentiated HCCs (20/39) and all dysplastic nodules were invisible. Of 22 iso-hypovascular lesions, 4 were visible on DW images and were poorly differentiated HCCs, whereas 18 were invisible and were dysplastic nodules (12/18) or well-differentiated HCCs (6/18).

Conclusion: A combination of hypovascularity and visibility on DW images can help distinguish poorly differentiated HCCs from low-grade hepatocellular lesions (dysplastic nodules and well-differentiated HCCs).