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Multiple Sclerosis: Magnetization Transfer MR Imaging of White Matter before Lesion Appearance on T2-weighted Images¹

¹ From the McConnell Brain Imaging Center, Room WB-315, Montreal Neurological Institute, 3801 University St, Montreal, Québec, Canada H3A 2B4 (G.B.P., S.N., K.J.W., D.P., G.S.F., J.P.A., D.L.A.), and the Department of Neurology, University of Siena, Italy (N.D.S.). Received December 8, 1998; revision requested February 9, 1999; final revision received September 29; accepted October 6. Supported in part by the Medical Research Council of Canada and Fonds de la Recherche en Santé du Québec. G.B.P., G.S.F., and D.L.A. are Killam Scholars. Address correspondence to G.B.P. (e-mail: bruce@bic.mni.mcgill.ca).

View larger version (115K): [in a new window]   Figure 1. Typical transverse MR images in a patient with MS. A, T1-weighted image (1,000/20). B, T2-weighted image (2,100/80). C, Intermediate-weighted image (2,100/30). D, MTR percentage difference image calculated by using T1-weighted imaging without and with an MT saturation pulse. E, Lesion map shows voxels defined on B and C. F, Lesion map shows coregistered voxels 31 months later.

View larger version (18K): [in a new window]   Figure 2. Scatterplot shows mean MTR in the head of the caudate nuclei (left and right sides averaged) for all studies in all patients with MS, plotted as a function of the time of the study (relative to the time of the first MTR study). No significant variation with time was observed, thus confirming the stability of our MTR measurements throughout this study.

View larger version (29K): [in a new window]   Figure 3. Scatterplot shows mean MTR of lesions demonstrated at T2-weighted MR imaging versus lesion age in 30 patients with MS and the mean linear regression line (slope = -1.7%/y, intercept = 30.1%). These data show a significant (P < .001) decline in lesion MTR with lesion age. + = primary-progressive subgroup,  = relapsing-remitting subgroup,  = secondary-progressive subgroup.

View larger version (18K): [in a new window]   Figure 4. Scatterplot shows mean MTR of lesions in patients with MS as seen on T2-weighted MR images (lesion age > 0) and in normal-appearing WM regions that become lesions (age < 0) versus time since detection on T2-weighted MR images. The diagonal line is the mean linear regression line (slope = -1.9%/y, intercept = 31.4%). These data show a significant (P < .001) decline in lesion MTR with time prior to lesion appearance on T2-weighted MR images. + = primary-progressive subgroup,  = relapsing-remitting subgroup,  = secondary-progressive subgroup.

View larger version (65K): [in a new window]   Figure 5a. Coregistered transverse T2-weighted MR images (2,000/80) in a single patient show the 2.5-year history of the MTR in an isolated new MS lesion (arrowhead). A, Baseline (initial) image; B, image obtained 6 months later; C, image obtained 24 months later. D, Graph shows the mean MTR in the new lesion plotted as a function of time since lesion appearance and indicates that the MTR was focally abnormal and declining in the prelesional phase. The mean MTR of WM in healthy subjects (Normal's WM) (41.3% ± 1.4) and in normal-appearing WM in patients with MS (MS NAWM) (38.1% ± 2.3) are indicated with arrows on the vertical axis. Error bars = SD.

View larger version (15K): [in a new window]   Figure 5b. Coregistered transverse T2-weighted MR images (2,000/80) in a single patient show the 2.5-year history of the MTR in an isolated new MS lesion (arrowhead). A, Baseline (initial) image; B, image obtained 6 months later; C, image obtained 24 months later. D, Graph shows the mean MTR in the new lesion plotted as a function of time since lesion appearance and indicates that the MTR was focally abnormal and declining in the prelesional phase. The mean MTR of WM in healthy subjects (Normal's WM) (41.3% ± 1.4) and in normal-appearing WM in patients with MS (MS NAWM) (38.1% ± 2.3) are indicated with arrows on the vertical axis. Error bars = SD.