Evaluation of Reproducibility of Diffusion Tensor Imaging in the Brachial Plexus at 3.0 T

The aim of this study was to evaluate the reproducibility of 3 T magnetic resonance imaging diffusion tensor imaging (DTI) of the brachial plexus in healthy subjects.

Ten healthy volunteers were included, and morphological and DTI sequences of the nerve roots of the brachial plexus from C5 to T1 of both sides were repeatedly acquired on a 3 T magnetic resonance system (MAGNETOM Skyra; Siemens Healthcare, Erlangen, Germany). A prototype diffusion-weighted single-shot echo-planar imaging sequence-enabling slice-specific shim adjustments was performed with b-values of 0 and 800 s/mm in 30 gradient directions, resulting in an acquisition time of about 6 minutes each in axial orientation. Between scans, subjects were moved and repositioned in the scanner, coils were reinserted, and new localizers were acquired. Image analysis was performed using MITK Diffusion software toolkit. Two independent readers performed diffusion data postprocessing, and regions of interest (ROIs) were set on the proximal postganglionic trunk at each spinal level, bilaterally to obtain values for fractional anisotropy (FA) and mean diffusivity (MD). Interreader and intrareader agreement as well as test-retest reproducibility of DTI metrics were assessed.

Intraclass correlation coefficients (ICCs) for interreader and intrareader agreement did not differ significantly between measurements for FA and MD. In particular, ICCs for interreader agreement of FA ranged from 0.741 to 0.961 and that of MD ranged from 0.802 to 0.998, and ICCs for intrareader agreement of FA ranged from 0.759 to 0.949 and that of MD ranged from 0.796 to 0.998. The test-retest reproducibility of DTI metrics showed an overall moderate to strong correlation (r > 0.707), with few minor exceptions, for both FA and MD values.

Diffusion tensor imaging metrics in the brachial plexus are reproducible. Future applications of DTI for a possible clinical use should be further investigated.