Ives R. Levesque

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Quantitative magnetization transfer imaging provides in vivo estimates of liquid and semisolid constituents of tissue, while estimates of the liquid subpopulations, including myelin water, can be obtained from multicomponent T(2) analysis. Both methods have been suggested to provide improved myelin specificity compared to conventional MRI. The goal of this(More)
Multiexponential T2 relaxation time measurement in the central nervous system shows a component that originates from water trapped between the lipid bilayers of myelin. This myelin water component is of significant interest as it provides a myelin-specific MRI signal of value in assessing myelin changes in cerebral white matter in vivo. In this article, the(More)
Quantitative magnetization-transfer imaging methods provide in vivo estimates of parameters of the two-pool model for magnetization-transfer in tissue. The goal of this study was to evaluate the reproducibility of quantitative magnetization-transfer imaging parameter estimates in healthy subjects. Magnetization-transfer-weighted and T(1) relaxometry data(More)
Novel MR image acquisition strategies have been investigated to elicit contrast within the thalamus, but direct visualization of individual thalamic nuclei remains a challenge because of their small size and the low intrinsic contrast between adjacent nuclei. We present a step-by-step specific optimization of the 3D MPRAGE pulse sequence at 7T to visualize(More)
PURPOSE To evaluate the reproducibility of multicomponent quantitative T(2) (QT2) measurements, in particular the myelin water fraction (MWF), to determine the sensitivity of this method for monitoring myelin changes in longitudinal studies and to provide a basis for correctly powering such studies. MATERIALS AND METHODS The de facto standard 32-echo(More)
PURPOSE Magnetization transfer in white matter (WM) causes biexponential relaxation, but most quantitative T1 measurements fit data assuming monoexponential relaxation. The resulting monoexponential T1 estimate varies based on scan parameters and represents a source of variation between studies, especially at high fields. In this study, we characterized WM(More)
PURPOSE There are many T1 mapping methods available, each of them validated in phantoms and reporting excellent agreement with literature. However, values in literature vary greatly, with T1 in white matter ranging from 690 to 1100 ms at 3 Tesla. This brings into question the accuracy of one of the most fundamental measurements in quantitative MRI. Our goal(More)
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