Multi-parametric classification of Alzheimer's disease and mild cognitive impairment: The impact of quantitative magnetization transfer MR imaging

Regional Analysis of the Magnetization Transfer Ratio of the Brain in Mild Alzheimer Disease and Amnestic Mild Cognitive Impairment

“…[5][6][7][8] DTI and magnetization transfer (MT) imaging allow assessment of the microstructure of the residual WM and GM in the same structures. [9][10][11][12][13][14][15][16] In particular, MT is a peculiar MR contrast that is based on the exchange of magnetization between free protons and protons bound to macromolecules and is influenced by the direct saturation of free protons by the radiofrequency pulse. 14,16 A more comprehensive analysis of the magnetization transfer phenomenon is possible with a quantitative approach, which, by use of different magnetization transfer models, enables determination of several parameters including the relative size of the restricted proton pool, the T2 relaxation time of the restricted pool and the relaxation times T1 and T2 of the free pool, and the forward exchange rate.…”

“…[9][10][11][12][13][14][15][16] In particular, MT is a peculiar MR contrast that is based on the exchange of magnetization between free protons and protons bound to macromolecules and is influenced by the direct saturation of free protons by the radiofrequency pulse. 14,16 A more comprehensive analysis of the magnetization transfer phenomenon is possible with a quantitative approach, which, by use of different magnetization transfer models, enables determination of several parameters including the relative size of the restricted proton pool, the T2 relaxation time of the restricted pool and the relaxation times T1 and T2 of the free pool, and the forward exchange rate. [14][15][16] In its simplest version, MT is obtained with acquisition of a pair of images without and with a specific radiofrequency offresonance prepulse followed by image subtraction and computation of the MT ratio.…”

“…14,16 A more comprehensive analysis of the magnetization transfer phenomenon is possible with a quantitative approach, which, by use of different magnetization transfer models, enables determination of several parameters including the relative size of the restricted proton pool, the T2 relaxation time of the restricted pool and the relaxation times T1 and T2 of the free pool, and the forward exchange rate. [14][15][16] In its simplest version, MT is obtained with acquisition of a pair of images without and with a specific radiofrequency offresonance prepulse followed by image subtraction and computation of the MT ratio. MT ratio is decreased in the temporal lobe and hippocampus of patients with AD independent from atrophy [9][10][11][12]14,17,18 ; is variably correlated with clinical severity, neuropsychological measurements, and disease duration [9][10][11][12] ; and appears capable to track progression of regional GM microstructural changes in AD.…”

“…[14][15][16] In its simplest version, MT is obtained with acquisition of a pair of images without and with a specific radiofrequency offresonance prepulse followed by image subtraction and computation of the MT ratio. MT ratio is decreased in the temporal lobe and hippocampus of patients with AD independent from atrophy [9][10][11][12]14,17,18 ; is variably correlated with clinical severity, neuropsychological measurements, and disease duration [9][10][11][12] ; and appears capable to track progression of regional GM microstructural changes in AD. 18 MT ratio was also reported to be decreased in the whole brain, whole temporal lobe, or temporal lobe GM and WM in patients with amnestic MCI as compared with agematched healthy control subjects.…”

“…10,11,19,20 However, in 2 studies that compared the MT ratio with several parameters calculated with quantitative MT approach in the hippocampus, enthorinal cortex, insula, and temporal neocortex, the former delivered the worst performance in differentiating AD, MCI, or healthy control subjects. 14,16 All the above MT imaging studies in AD and MCI used whole brain or temporal lobe segmentation, or involved analysis of manually drawn region of interest or VOI. Voxelwise analysis of MT ratio maps offers the advantage of an automatic whole-brain, voxel-based analysis without a priori assumptions about the specific region under investigation.…”