3D quantitative synthetic MRI for assessing Alzheimer's clinical syndrome, subjective cognitive impairment, and mild cognitive impairment.

PURPOSE: For Alzheimer's Clinical Syndrome (ACS) and early cognitive decline (mild and subjective cognitive impairment, MCI/SCI), we used three-dimensional (3D) quantitative synthetic magnetic resonance imaging (MRI) with an interleaved Look-Locker acquisition sequence and a T2 preparation pulse (QALAS), which can acquire quantitative parameters in a single scan, to investigate the potential of quantitative parameters to add supplemental information to the structural imaging.

METHODS: Twenty-four ACS patients, 19 patients with MCI/SCI, and 24 age- and sex-matched healthy controls (HCs) underwent MRI. The differences in longitudinal relaxation time (qT1), transverse relaxation time (qT2), proton density (PD), myelin volume fraction (MVF), and gray matter volume among the groups were evaluated using voxel-based quantification (VBQ) and voxel-based morphometry (VBM). Logistic regression analyses were developed to distinguish between the ACS, MCI/SCI, and HC groups.

RESULTS: In the VBM and VBQ analyses, patients with ACS had significantly lower gray matter volume and MVF and higher qT1, qT2, and PD compared to the HC group. Compared to VBM, VBQ analysis identified broader areas of significance specifically in the insula and cerebellum vermis, known to atrophy as the disease progresses. Subtle differences in PD and MVF were observed between MCI/SCI and HC groups, and the AUC was significantly higher when the quantitative measures obtained with 3D-QALAS were combined than when logistic regression was performed with the brain volume alone (quantitative measures and volume: 0.79; volume: 0.58; p = 0.034).

CONCLUSIONS: 3D-QALAS integrates quantitative relaxometry and myelin-sensitive metrics reflecting water content and myelin integrity with structural information.