Peripheral nerve diffusion tensor imaging is reliable and reproducible.

Objective: To determine the reliability and reproducibility of peripheral nerve diffusion tensor imaging (DTI) in healthy subjects.

Methods: We assessed the test-retest and interrater reliability studies of peripheral nerve DTI in a cohort of 12 healthy subjects (mean age 44.0 years, range 26-71 years). Magnetic resonance imaging (MRI) studies were performed on a 3T scanner (MR750, GE Healthcare). DTI and T1 -weighted sequences were performed on the tibial and peroneal nerves in the knee. Each subject was scanned on three separate occasions. Image analyses were performed at two anatomic positions: the level of the lateral femoral condyle (position 1), and the superior pole of the patella (position 2). Analysis was performed using three software packages ("raters"): FuncTools, FSL, and Diffusion Toolkit. Metrics obtained included fractional anisotropy (FA), axial diffusivity (AD), and radial diffusivity (RD).

Results: DTI metrics were not significantly different between each measurement position, except peroneal nerve AD and tibial nerve RD were higher at position 1 (P = 0.02 and 0.04, respectively). There was no significant difference in DTI metrics between male and female subjects (P = 0.10-0.99). The test-retest reliability of DTI metrics was high, maximal for FA (intraclass correlation coefficient [ICC] = 0.96). ICC values for individual DTI metrics were similar between each measurement position, except that tibial nerve AD was significantly higher at position 2 (P = 0.03). Interrater reliability was also high (ICC = 0.95-0.96).

Conclusions: We found peripheral nerve DTI to be reliable and reproducible, with few effects related to the postprocessing package used.