Multiple sclerosis: Comparison of trace apparent diffusion coefficients with NIR enhancement pattern of lesions

BACKGROUND AND PURPOSE: Diffusion-weighted MR imaging and the trace apparen t diffusion coefficient (ADC) provide important structural information abou t tissues. The purpose of this study was to investigate the relationship be tween trace ADC values and the enhancement pattern of multiple sclerosis (M S) lesions. METHODS: Ninety-six lesions, identified in 24 patients with MS, were charac terized by their enhancement pattern on contrast-enhanced T1-weighted MR im ages. There were 57 nonenhancing lesions (NELs), 28 homogeneously enhancing lesions (HELs), and 11 ring-enhancing lesions (RELs), The trace ADC means for each type of lesion and for normal-appearing white matter (NAWM) were c alculated and compared using Student's t-test. RESULTS: The mean trace ADC values for HELs (mean, 7.7 x 10(-10) m(2)s(-1); SD, 1.4 x 10(-10) m(2)s(-1)) were less than those for RELs (mean, 1.2 x 10 (-9) m(2)s(-1); SD, 3.5 x 10(-10) m(2)s(-1)) and NELs (mean, 1.3 x 10(-9) m (2)s(-1); SD, 2.6 x 10(-10) m(2)s(-1)). There was a significant difference between the mean trace ADC values of HELs and RELs as well as between those for HELs and NELs, There was also a significant difference in the mean tra ce ADC values between all lesion types and NAWM (mean, 6.9 x 10(-10) m(2)s( -1); SD, 5.0 x 10(-11) m(2)s(-1)). CONCLUSION: We found a predictable relationship between mean trace ADC and the pattern of enhancement in MS lesions, corresponding to reported histopa thologic differences in myelination between lesion types and magnetization transfer ratios.