Diffusion-weighted MR Imaging for the Regional Characterization of Liver Tumors

Purpose: To determine if diffusion-weighted (DW) magnetic resonance (MR) imaging with measurements of the apparent diffusion coefficient (ADC), pure diffusion coefficient, perfusion-related diffusion coefficient, and perfusion fraction can be used to differentiate between viable tumor and fibrous and necrotic regions within malignant liver tumors. Material and Methods: The prospective study was approved by the institutional review board, and informed consent was obtained from all patients. Forty-eight patients with 51 malignant tumors were assessed. MR images of the liver were obtained by using DW imaging with 11 b factors (0-500 sec/mm(2)) and gadolinium-enhanced three-dimensional gradient-echo T1-weighted imaging. Tumors were segmented into viable tumor and fibrous and necrotic regions according to the enhancement pattern after injection of a nonspecific gadolinium chelate and, in surgically removed lesions, results of histopathologic correlation. The ADC, pure diffusion coefficient, perfusion-related diffusion coefficient, and perfusion fraction were calculated, and values were compared between viable tumor and fibrous and necrotic regions with the Kruskal-Wallis test followed by the Dunn multiple comparison test. Results: The pure diffusion coefficient differed significantly between regions of viable tumor tissue and fibrosis (1.16 x 10(-3) mm(2)/sec +/- 0.29 and 1.48 x 10(-3) mm(2)/sec +/- 0.31, respectively; P = .016) and between regions of viable tumor tissue and necrosis (1.70 x 10(-3) mm(2)/sec +/- 0.49, P = .002). There was a significantly lower perfusion fraction in necrotic regions (14% +/- 6) than in viable tumor regions (21% +/- 8, P = .005), but the perfusion fraction of the fibrous regions (21% +/- 7) did not differ significantly from that of the other two regions. ADCs and perfusion-related diffusion coefficients did not differ significantly among the three regions. Conclusion: Results of this study show that viable tumor regions in malignant liver tumors can be differentiated from fibrous and necrotic regions with use of the pure diffusion coefficient but not with the other diffusion parameters. (c) RSNA, 2012