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Microvascular Abnormality in Relapsing-Remitting Multiple Sclerosis: Perfusion MR Imaging Findings in Normal-appearing White Matter¹

¹ From the Departments of Radiology (M.L., A.M.S., Y.G., J.S.B., G.J., L.J.M., R.I.G.) and Neurology (J.H.), New York University Medical Center, MRI Department, Schwartz Building, Basement HCC, 530 First Ave, New York, NY 10016. Received June 24, 2003; revision requested September 3; revision received October 16; accepted November 12. Supported by National Institutes of Health grants RO1CA093992, NS29029, NCRR M01 RR00096 GCRC, and R37 NS 29029–11. Address correspondence to M.L. (e-mail: lawm01@med.nyu.edu).

View larger version (104K): [in a new window]   Figure 1a. (a) Transverse gradient-echo echo-planar MR image (1,000/54) with CBV map overlay shows the elliptical regions of NAWM that were examined: periventricular NAWM (A), intermediate NAWM (B), and subcortical NAWM (C). In the perfusion color overlay map, areas of no color represent baseline white matter perfusion, green represents threshold gray matter perfusion, yellow represents increased perfusion, and red represents maximal perfusion. This is to ensure that ROIs are placed in the NAWM and lesions and vascular and gray matter structures are avoided. (b) Close-up of area in white box in a. To optimize reproducibility, five measurements were obtained from each of the three locations. These five CBV, CBF, and MTT measurements were recorded and averaged. ROIs were fixed in size (radius = 1 image pixel, 1.8 mm) and placed to avoid arterial or venous structures in NAWM, particularly in the periventricular and subcortical regions. Hence, each ROI has an in-plane resolution of 2 pixels. The location of ROI placement was at the same section position in patients with RR-MS and in control patients at the level of the ventricles. The ROIs were placed after visual coregistration with the transverse T2-weighted and fluid-attenuated inversion recovery MR images to ensure that lesions were not included in the ROI. INT = intermediate NAWM, PV = periventricular NAWM, SC = subcortical NAWM.

View larger version (104K): [in a new window]   Figure 1b. (a) Transverse gradient-echo echo-planar MR image (1,000/54) with CBV map overlay shows the elliptical regions of NAWM that were examined: periventricular NAWM (A), intermediate NAWM (B), and subcortical NAWM (C). In the perfusion color overlay map, areas of no color represent baseline white matter perfusion, green represents threshold gray matter perfusion, yellow represents increased perfusion, and red represents maximal perfusion. This is to ensure that ROIs are placed in the NAWM and lesions and vascular and gray matter structures are avoided. (b) Close-up of area in white box in a. To optimize reproducibility, five measurements were obtained from each of the three locations. These five CBV, CBF, and MTT measurements were recorded and averaged. ROIs were fixed in size (radius = 1 image pixel, 1.8 mm) and placed to avoid arterial or venous structures in NAWM, particularly in the periventricular and subcortical regions. Hence, each ROI has an in-plane resolution of 2 pixels. The location of ROI placement was at the same section position in patients with RR-MS and in control patients at the level of the ventricles. The ROIs were placed after visual coregistration with the transverse T2-weighted and fluid-attenuated inversion recovery MR images to ensure that lesions were not included in the ROI. INT = intermediate NAWM, PV = periventricular NAWM, SC = subcortical NAWM.

View larger version (26K): [in a new window]   Figure 2. Graph shows signal intensity-versus-time curves measured in periventricular NAWM in a patient with RR-MS and a control patient. In both cases, injection of gadopentetate dimeglumine was performed at 10 seconds (arrow). The time to peak and MTT are significantly delayed (P < .001) in the patient with RR-MS, and the signal intensity curve is delayed and prolonged compared with the signal intensity curve for the control patient.

View larger version (29K): [in a new window]   Figure 3. Bar graph illustrates the significant decrease in CBF in periventricular, intermediate, and subcortical NAWM in patients with RR-MS (black bars) compared with the CBF in these regions in control patients (white bars). Normal values and CBF threshold values for white matter hypoperfusion, oligemia, and ischemia (39) are shown on the left side of the graph. CBF values in the NAWM of patients with RR-MS are in the oligemic hypoperfusion range without being in the frankly ischemic range.