Purpose To evaluate the accuracy and reproducibility of quantitative chemical shift-encoded MRI (CSE-MRI) to quantify proton-density fat-fraction (PDFF) in a fat-water phantom across sites, vendors, field strengths and protocols. Methods Six sites (three vendors: GE/Philips/Siemens) participated in this study. A phantom containing multiple vials with various oil-water suspensions (PDFF:0–100%) was built, shipped to each site and scanned at 1.5T and 3T using two CSE protocols per field strength. Confounder-corrected PDFF maps were reconstructed using a common algorithm. To assess accuracy, PDFF bias and linear regression with the known PDFF were calculated. To assess reproducibility, measurements were compared across sites, vendors, field strengths and protocols using analysis of covariance (ANCOVA), Bland-Altman analysis and the intra-class correlation coefficient (ICC). Results PDFF measurements showed overall absolute bias (across sites, field strengths and protocols)=0.22% with 95% CI:(0.07%,0.38%), and R2>0.995 relative to the known PDFF at each site, field strength and protocol (slopes: 0.96–1.02, intercepts: −0.56%–1.13%). ANCOVA did not show effects of field strength (p=0.36), or protocol (p=0.19). There was a significant effect of vendor (F=25.13,p=1.07×10−10), with bias= −0.37% (Philips) and −1.22% (Siemens) relative to GE. The overall ICC was 0.999. Conclusion CSE-based fat quantification is accurate and reproducible across sites, vendors, field strengths and protocols.

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The aim of this study was to investigate regional differences between morphologic and functional changes in patients with mild dementia with Lewy bodies (DLB) compared with those with Alzheimer's disease (AD). Methods: Twenty patients with very mild DLB (mean age, 74.5 y; mean Mini-Mental State Examination [MMSE] score, 24.0), 20 patients with very mild AD (mean age, 74.1 y; mean MMSE score, 24.0), and 20 age-and sex-matched healthy volunteers (normal controls [NC]) underwent both 18 F-FDG PET and 3-dimensional spoiled gradient echo MRI. Fully automatic volumetry of the MRI data was used to obtain whole brain, hippocampal, occipital, and striatal volumes, which were compared with the results of a similar analysis of glucose metabolic data. Results: In DLB patients, volumetric data indicated a significant volume decrease in the striatum, whereas 18 F-FDG PET showed significant glucose metabolic reductions in the temporal, parietal, and frontal areas-including in the occipital lobe-compared with those in the NC group. In contrast, in AD patients, both the hippocampal volume and glucose metabolism were significantly decreased, whereas the occipital volume and metabolism were preserved. Conclusion: Comparison of very mild DLB and AD revealed different morphologic and metabolic changes occurring in the medial temporal lobes and the occipital lobe, demonstrating characteristic pathophysiologic differences between these 2 diseases. Dement ia with Lewy bodies (DLB), a clinical entity of primary degenerative dementia pathologically characterized by the presence of Lewy bodies in cortical, subcortical, and brain-stem structures, is the second most common degenerative dementia after Alzheimer's disease (AD). In the DLB brain, the occipital lobe is not affected histopathologically but metabolic or perfusional reduction is present in the occipital lobe (1-3), whereas the medial temporal limbic area is minimally affected histopathologically (4-6). In the mild AD brain, neuropathologic changes predominantly affect the neocortical association area and medial temporal limbic area. These histopathologic changes lead to focal atrophy and can be demonstrated by MRI (7,8), whereas metabolic reductions are demonstrated in the neocortical association area by PET (9,10). However, there has been controversy as to whether medial temporal metabolic reductions exist in the early stage of AD (11-16). The localization method using the region of interest (ROI) showed that significant medial temporal hypometabolism may be seen in AD, even in the incipient amnestic mildcognitive-impairment stage (13-15). These morphologic and functional changes in the same patients have been studied in AD patients (16), although, to our knowledge, there are no reports describing these investigations in the same DLB patients.By analyzing both MR images and glucose metabolic PET in patients with mild DLB or AD in this study-using automatic volumetric and voxel-based techniques for MR images and metabolic values of regional structures and the voxel-based techniq...