Complementary information from multi-exponential T2 relaxation and diffusion tensor imaging reveals differences between multiple sclerosis lesions

While conventional magnetic resonance imaging (MRI) has long been used to study multiple sclerosis (MS), more sensitive and specific approaches to studying both MS lesions and normal appearing white matter (NAWM) are needed to gain a better understanding of the pathogenesis of the disease. Two MRI techniques thought to offer insight regarding myelin and axonal integrity are T2 relaxation and diffusion tensor imaging (DTI). In this study, metrics obtained from T2 relaxation (specifically myelin water content (MWC) and long-T2 fraction) and DTI experiments (in particular the fractional anisotropy, mean diffusivity , parallel diffusivity λ||, and perpendicular diffusivity λ⊥) were compared for 19 MS patients within both lesion and contralateral NAWM with the goal of better understanding how each of the measures are affected by pathology. In particular, it was successfully determined that the detection of a long-T2 signal within an MS lesion is indicative of a different underlying pathology than is present in lesions without long-T2 signal. All of the diffusion metrics were significantly different in lesions with a long-T2 signal than in those without. While no significant correlations were found between MWC and , λ|| or λ⊥ in NAWM (R2 = 0.02–0.04, p > 0.07), and only weak correlations were found in lesions without long-T2 signal (R2 = 0.05–0.14, p < 0.04), strong correlations were observed in lesions exhibiting long-T2 signal (R2 = 0.54–0.61, p < 0.0001).