A MULTICENTER STUDY OF THE CORRELATION BETWEEN THE QUANTITATIVE SUSCEPTIBILITY MAPPING OF MAGNETIC RESONANCE IMAGING AND AMYLOID POSITRON EMISSION TOMOGRAPHY

Several studies of quantitative susceptibility mapping (QSM) have reported that Alzheimer's disease (AD) patients have increased magnetic susceptibility in the brain, reflecting the pathological accumulation of iron in Aβ plaques. The purpose of this study was to examine the correlation between the increased susceptibility of QSM and Aβ deposition of amyloid positron emission tomography (PET). Twenty-six patients were prospectively included in this study (age range 52–88 years, median 77, M:F=13:13). The clinical diagnosis were as follows: 16 dementia cases (7 AD, 2 AD+dementia with Lewy bodies (DLB), 2 DLB+vascular dementia, 2 frontotemporal dementia, 1 DLB, 2 unknown), 9 mild cognitive impairment cases (MCI) (8 MCI due to AD, 1 MCI due to AD+DLB), and one cognitively normal case. Magnetic resonance imaging was performed using 3-T scanners. Amyloid PET imaging was performed using 18F-flutemetamol. Both QSM and PET images were spatially normalized, and region of interest analysis was performed using an automated anatomical labeling template. After 94 supratentorial regions were averaged left and right, intra-patient and inter-patient correlations between QSM and PET were analyzed for 47 regions using Pearson's correlation coefficient. Based on amyloid PET, 15 patients were Aβ positive and 11 were Aβ negative. The intra-patient correlation coefficient of the Aβ-positive patients ranged from 0.16 to 0.54 (average 0.40), whereas that of the Aβ-negative patients ranged from 0.35 to 0.70 (average 0.54). Positive inter-patient correlations were noted in 27 of the 47 regions, and moderate correlations (r>0.30) were noted in 5 regions (Fig. 1): the cuneus (r=0.50), rolandic operculum (r=0.42), triangular part of the inferior frontal gyrus (r=0.37), anterior cingulate gyrus (r=0.33), and rectal gyrus (r=0.30). When averaged for these 5 regions, the correlation was moderate (r=0.56), and receiver operator characteristic analysis performed to predict Aβ positivity revealed that the sensitivity was 0.67, the specificity was 0.81, and the area under the curve was 0.76 (Fig. 2).