Quantitative susceptibility mapping to evaluate the early stage of Alzheimer's disease

Abstract

The objective of this study was to evaluate susceptibility changes caused by iron accumulation in cognitive normal (CN) elderly, those with amnestic mild cognitive impairment (aMCI), and those with early state AD, and to compare the findings with gray matter volume (GMV) changes caused by neuronal loss. The participants included 19 elderly CN, 19 aMCI, and 19 AD subjects. The voxel-based quantitative susceptibility map (QSM) and GMV in the brain were calculated and the differences of those insides were compared among the three groups. The differences of the QSM data and GMVs among the three groups were investigated by voxel-based and region of interest (ROI)-based comparisons using a one-way analysis of covariance (ANCOVA) test with the gender and age as covariates. Finally, a receiver-operating-characteristic (ROC) curve analysis was performed. The voxel-based results showed that QSM demonstrated more areas with significant difference between the CN and AD groups compared to GMV. GMVs were decreased, but QSM values were increased in aMCI and AD groups compared with the CN group. QSM better differentiated aMCI from CN than GMV in the precuneus and allocortex regions. In the accumulation regions of iron and amyloid β, QSM can be used to differentiate between CN and aMCI groups, indicating a useful an auxiliary imaging for early diagnosis of AD.

Keywords: Alzheimer's disease (AD); Gray matter volume; Mild cognitive impairment (MCI); Quantitative susceptibility mapping (QSM).

Fig. 1

Representative maps of gray matter volumes (A, C, and E) and the segmented tissue components of QSM maps (B, D, and F). CN, cognitive normal; aMCI, amnestic mild cognitive impairment; AD, Alzheimer's disease.

Fig. 2

Results of the voxel-based analysis of gray matter volume (GMV, A) and quantitative susceptibility mapping (QSM, B) values between the cognitive normal (CN) and Alzheimer's disease (AD) subjects. GMV (A) obtained from a 3D T1-weighted imaging was higher in CN than that in AD, but QSM value (B) was higher in AD than that in CN. There were no significant differences for both GMVs and QSM values between other subject groups.

Fig. 3

Mean values of percentage changes of gray matter volumes (GMVs: A) and QSM values (B) in the specific regions of interest on the amnestic mild cognitive impairment (aMCI) and Alzheimer's disease (AD) against the cognitive normal (CN) subjects. The result of statistically significant differences of GMV and QSM are indicated by circle (○) for the comparison between CN and aMCI groups, of plus (+) for the comparison between aMCI and AD group, and of asterisk (*) for the comparison between CN and AD group. GMV was lower in aMCI and AD than that in CN, but QSM value was higher in aMCI and AD than in CN.

Fig. 4

Results of ROC curve analysis of QSM values (A, B) obtained from the special region-of-interests (ROIs) to differentiate amnestic mild cognitive impairment (aMCI) subjects from cognitive normal (CN) subjects in the subjects and results of comparison of ROC curves (C, D) between QSM and GMV at the specific regions. (A) and (B) show the significant results of ROC curve analysis of QSM data in the well-known iron accumulation regions and the well-known amyloid β accumulation regions, respectively. (C) and (D) show the result of comparison of ROC curves to compare QSM and GMV in the precuneus and the allocortex regions, respectively.