Purpose To describe the spatial distribution of liver fat, using magnetic resonance imaging (MRI)-estimated proton density fat fraction (PDFF), in adults with non-alcoholic fatty liver disease (NAFLD). Materials and Methods This IRB-approved, HIPAA-compliant study prospectively enrolled fifty adults (30 women, 20 men) with biopsy-proven NAFLD. Hepatic PDFF was measured by low-flip-angle multiecho spoiled gradient-recalled-echo MRI at 3T. Three non-overlapping regions of interest were placed within each liver segment. Statistical analyses included Pearson’s correlation, multivariable linear regression, and permutation-based paired tests. Results The study population’s mean whole-liver PDFF was 16.1% (range: 1.6–39.6%). The mean whole-liver PDFF variability was 1.9% (range: 0.7–4.5%). Higher variability was associated with higher PDFF (r=0.34, p=0.0156). The mean PDFF was significantly higher in the right lobe than the left (16.5% vs. 15.3%, p=0.0028). The mean PDFF variability was higher in the left lobe than the right (1.86% vs. 1.28%, p<0.0001). Segment II had the lowest mean segmental PDFF (14.8%); segment VIII had the highest (16.7%). Segments V (0.71%) and VI (0.70%) had the lowest mean segmental PDFF variability; segment II had the highest (1.32%). Conclusion In adult NAFLD there are small but significant differences in fat content and variability between lobes and some of the segments.

Methods 2 and 3 accurately assess FF. Strong reproducibility across magnet type and strength render them suitable for use in multicenter trials and longitudinal assessments.

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The cerebral vasculature incorporates several fail-safes that must be breached before an irreversible ischemic event takes place. In particular, when autoregulatory vasodilatation fails secondary to falling cerebral perfusion pressure (CPP; stage I hemodynamic failure), increases in the oxygen extraction fraction work to maintain the cerebral metabolic rate of oxygen. Previously, failure of this mechanism, stage II hemodynamic failure, or misery perfusion, has been imaged via positron emission tomography/computed tomography (PET/CT). Current susceptibility-weighted sequences (SWI) allow for more efficient imaging of this physiology. In this case, we identify an incident of reversible ischemia caused by spontaneous carotid artery dissection using a combination of diffusion weighted imaging (DWI) and SWI. The level of hemodynamic failure identified by the imaging sequences elevated the urgency of neurointervention, expediting the patient's arrival to the neurointerventional table and thus avoiding impending irreversible ischemia.

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