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 specificity to the most destructive aspects of multiple sclerosis. In this study, we obtained brain mean diffusivity ((D) over bar) and fractional anisotropy histograms of patients with multiple sclerosis to compare them with those of healthy volunteers and to investigate the correlation between diffusion tenser MR imaging histogram-derived measures and the level of disability and quantities derived from conventional MR imaging. METHODS: Dual-echo and diffusion tenser MR images were obtained from 78 patients with relapsing-remitting, secondary progressive, or primary progressive multiple sclerosis and from 20 healthy control volunteers. After obtaining mean diffusivity ((D) over bar) and fractional anisotropy images and image coregistration, (D) over bar and fractional anisotropy histograms were crested. From each histogram, the following measures were derived: the average (D) over bar and fractional anisotropy, the histogram peak heights, and the histogram peak locations. RESULTS: All the (D) over bar and fractional anisotropy histogram-derived measures 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 average (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 correlated with fractional anisotropy histogram peak position (r = - 0.6, P = .01). Significant correlations were also found between T2 lesion load and various diffusion tenser MR quantities. CONCLUSION This study shows that brain ((D) over bar) and fractional anisotropy histograms are different for patients with multiple sclerosis compared with control volunteers. This study also shows that quantities derived from diffusion tenser MR imaging are correlated with disability in patients with relapsing-remitting multiple sclerosis and secondary progressive multiple sclerosis, suggesting that they might serve as additional measures of outcome when monitoring multiple sclerosis evolution in these patients.