Multicenter Measurements of T 1 Relaxation and Diffusion Tensor Imaging: Intra and Intersite Reproducibility.

BACKGROUND AND PURPOSE: Quantitative T1 and diffusion tensor imaging (DTI) may provide information about pathological changes underlying disability and progression in diseases like multiple sclerosis (MS). Imaging the corpus callosum (CC), a primary site of damage in MS with a critical role in interhemispheric connectivity, may be useful for assessing overall brain health, prognosis, and therapy efficacy. We assessed the feasibility of multisite clinical trials using advanced MRI by examining the intra and intersite reproducibility of T1 and DTI measurements in the CC and segmented white matter (WM).

METHODS: Five healthy volunteers were scanned twice within 24 hours at six 3T sites. Coefficients of variation (COVs) and intraclass correlation coefficients (ICCs) for CC and WM T1 , fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (Dax ), and radial diffusivity (Drad ) assessed intrasite and intersite reliability.

RESULTS: CC and WM T1 showed excellent intrasite reproducibility with low COVs (mean = .90% and .89%, respectively) and good ICCs (CC = .78, WM = .90). T1 also demonstrated intersite reliability (low COVs: CC = 2.4%, WM = 1.8%; moderate ICCs: CC = .43, WM = .69). DTI had low intrasite COVs (CC: FA = 1.3%, MD = 1.5%, Dax = 1.4%, Drad = 2.2%; WM: FA = .9%, MD = .9%, Dax = .7%, Drad = 1.2%) and high intrasite ICCs (CC: FA = .95, MD = .97, Dax = .94, Drad = .97; CC: FA = .9, MD = .66, Dax = .88, Drad = .63), indicating excellent intrasite reproducibility. DTI also showed excellent intersite reliability with low COVs (CC: FA = 2.1%, MD = 4.1%, Dax = 3.4%, Drad = 5.3%, WM: FA = 1.3%, MD = 1.9%, Dax = 1.8%, Drad = 2.1%,) and good ICCs (CC: FA = .90, MD = .84, Dax = .72, Drad = .90; WM: FA = .83, MD = .34, Dax = .62, Drad = .41).

CONCLUSIONS: T1 and DTI measures are reproducible using equivalent MRI scanners and sequence protocols. Using a similar MR system, it is feasible to carry out multicenter studies using T1 and DTI to evaluate changes within the CC and WM.