T1 mapping in Alzheimer’s disease: a quantitative MRI study with amyloid-PET correlation
Quantitative T1 mapping (qT1) is a magnetic resonance imaging (MRI) biomarker of brain microstructural changes; however, its application in Alzheimer disease (AD) remains limited. We compared cortico-limbic qT1 values between patients with AD and healthy controls (HCs) and examined their relationship with amyloid burden measured by amyloid-positron emission tomography (PET). We retrospectively identified subjects with mild cognitive impairment due to AD and HCs who underwent 3-T MRI, including a compressed-sensing MP2RAGE sequence, generating three-dimensional T1-weighted images and qT1 maps. Amyloid-PET was available for 16 patients. Hippocampal qT1 and volume were compared between groups, adjusting for age and sex; analyses were repeated after stratifying patients by Mini-Mental State Examination (MMSE). Voxel-wise group comparison was performed using SPM 12. The qT1-standardized uptake value ratio (SUVr) association was assessed with a linear mixed-effects model applied to voxel-level data, accounting for partial volume effects. Thirty-three AD subjects, aged 69.3 ± 8.2 years (mean ± standard deviation), 18 females, and 22 HCs aged 70.5 ± 13.3 years, 15 females, were evaluated. Regional hippocampal qT1 was higher in AD (1,398 ± 53.0 ms versus 1,349 ± 53.4 ms; p = 0.002), without difference across cognitive subgroups stratified by MMSE. AD subjects exhibited increased qT1 in mesial temporal gray matter and temporo-parieto-occipital cortices (1,448 ± 55.7 ms versus 1,344 ± 51.6 ms; p < 0.001). Voxel-level modelling revealed a positive association between qT1 and amyloid-PET SUVr (p < 0.001; d = 0.223). qT1 mapping can be sensitive to changes related to brain amyloidosis, supporting its role as a promising, noninvasive imaging biomarker in AD. Question Can qT1 mapping detect AD-related microstructural changes in the cortico-limbic gray matter? Findings Participants with AD showed increased cortico-limbic qT1 values. A subtle yet consistent positive association was observed between cortical qT1 values and amyloid-PET SUVr. Relevance statement qT1 mapping captures microstructural tissue alterations related to amyloid pathology in Alzheimer’s disease, supporting its role as a potential non-invasive imaging biomarker in this condition.