Diffusion-weighted MR neurography of extremity nerves with unidirectional motion-probing gradients at 3 T: feasibility study.

OBJECTIVE: The objective of our study was to show the feasibility and performance of diffusion-weighted MR neurography (MRN) of extremity nerves with unidirectional motion-probing gradients at 3 T.

SUBJECTS AND METHODS: Forty-seven healthy volunteers and 10 patients underwent diffusion-weighted MRN of extremity nerves with unidirectional motion-probing gradients (anterior-posterior direction only) on a 3-T unit. Images were displayed using a maximum-intensity-projection technique. Two radiologists blindly and independently evaluated the imaging quality of extremity nerves on diffusion-weighted MRN images using a 4-point grading scale, with 4 indicating excellent quality and 1 indicating poor quality, and evaluated the relation of the lesion to adjacent nerves in patients.

RESULTS: In volunteers, the long trajectories of major extremity nerves, including the radial, median, ulnar, sciatic, tibial, and common peroneal nerves, could be visualized 3D on diffusion-weighted MRN images. The mean imaging quality scores of all nerves for observers 1 and 2 were 3.68 ± 0.70 (SD) and 3.70 ± 0.66, respectively. Interobserver agreement was good (κ = 0.774). In patients, there was no discrepancy in imaging quality scores between observers. Scores of all nerves were 2-4 except in two patients with neurofibromatosis and one patient who underwent imaging soon after surgery. The extent of the lesions and the relationship of the lesions to the adjacent nerves were clearly depicted on diffusion-weighted MRN images of all patients.

CONCLUSION: This preliminary study shows that 3-T diffusion-weighted MRN with unidirectional motion-probing gradients is feasible for 3D visualization of major extremity nerves. Diffusion-weighted MRN may enable nerve depiction and allow assessment of the anatomic relationship between lesions with diffusion restriction and adjacent nerves.