Mean diffusivity and fractional anisotropy histograms of patients with multiple sclerosis

BACKGROUND AND PURPOSE: Compared with conventional T2-weighted MR imaging, diffusion tenser MR imaging provides quantitative indices with increased sp ecificity to the most destructive aspects of multiple sclerosis. In this st udy, we obtained brain mean diffusivity ((D) over bar) and fractional aniso tropy histograms of patients with multiple sclerosis to compare them with t hose of healthy volunteers and to investigate the correlation between diffu sion tenser MR imaging histogram-derived measures and the level of disabili ty and quantities derived from conventional MR imaging. METHODS: Dual-echo and diffusion tenser MR images were obtained from 78 pat ients with relapsing-remitting, secondary progressive, or primary progressi ve multiple sclerosis and from 20 healthy control volunteers. After obtaini ng mean diffusivity ((D) over bar) and fractional anisotropy images and ima ge coregistration, (D) over bar and fractional anisotropy histograms were c rested. From each histogram, the following measures were derived: the avera ge (D) over bar and fractional anisotropy, tile histogram peak heights, and the histogram peak locations. RESULTS: All the (D) over bar and fractional anisotropy histogram-derived m easures were different between patients and control at a significance level of P < .001. No differences were found in any of the considered quantities among the three multiple sclerosis phenotypes. In patients with relapsing- remitting multiple sclerosis, disability nas correlated with histogram aver age (D) over bar (r = 0.4, P = .01) and peak height (r = -0.4 P = .01). In patients with secondary progressive multiple sclerosis, disability was corr elated with fractional anisotropy histogram peak position (r = - 0.6, P = . 01). Significant correlations were also found between T2 lesion load and va rious diffusion tenser MR quantities. CONCLUSION This study shows that brain ((D) over bar) and fractional anisot ropy histograms are different for patients with multiple sclerosis compared with control volunteers. This study also shows that quantities derived fro m diffusion tenser MR imaging are correlated with disability in patients wi th relapsing-remitting multiple sclerosis and secondary progressive multipl e sclerosis, suggesting that they might serve as additional measures of out come when monitoring multiple sclerosis evolution in these patients.