Intravoxel Incoherent Motion Diffusion-weighted Imaging in Nonalcoholic Fatty Liver Disease: A 3.0-T MR Study

Abstract

PURPOSE: To compare pure molecular diffusion, D, perfusion-related diffusion, D*, and perfusion fraction, f, determined from diffusion-weighted (DW) magnetic resonance (MR) imaging on the basis of the intravoxel incoherent motion (IVIM) theory in patients with type 2 diabetes with and without liver steatosis. MATERIALS AND METHODS: This prospective study was approved by the appropriate ethics committee, and written informed consent was obtained from all patients. Between December 2009 and September 2011, 108 patients with type 2 diabetes (51 men, 57 women; mean age, 50 years) underwent 3.0-T single-voxel point-resolved proton MR spectroscopy of the liver (segment VII) to calculate the liver fat fraction from water (4.76 ppm) and methylene (1.33 ppm) peaks, corrected for T1 and T2 decay. Steatosis was defined as a liver fat fraction of at least 5.56%. DW imaging was performed by using a single-shot echo-planar sequence with 11 b values (0, 5, 15, 25, 35, 50, 100, 200, 400, 600, 800 sec/mm2). Liver D, D*, and f were measured and compared in patients with and patients without steatosis (Mann-Whitney test). RESULTS: The mean liver fat fraction was 7.8% (standard deviation, 9%; range, 0.99%-45%). Forty patients had liver steatosis. D was significantly lower in steatotic compared with nonsteatotic livers (mean, 1.03×10(-3) mm2/sec±0.23 [standard deviation] vs 1.24×10(-3) mm2/sec±0.15, respectively; P<.0001), as was D* (mean, 72.2×10(-3) mm2/sec±61.4 vs 110.6×10(-3) mm2/sec±79; P=.0025). However, f was significantly higher in steatotic compared with nonsteatotic livers (mean, 33.8%±9.4 vs 26.9%±8.8; P=.0003). CONCLUSION: D is significantly decreased in steatosis. The reduction in D* reflects decreased liver parenchymal perfusion in steatosis. Therefore, steatosis can affect diffusion parameters obtained with IVIM.