Three-dimensional display of peripheral nerves in the wrist region based on MR diffusion tensor imaging and maximum intensity projection post-processing.

OBJECTIVES: To achieve 3-dimensional (3D) display of peripheral nerves in the wrist region by using maximum intensity projection (MIP) post-processing methods to reconstruct raw images acquired by a diffusion tensor imaging (DTI) scan, and to explore its clinical applications.

METHODS: We performed DTI scans in 6 (DTI6) and 25 (DTI25) diffusion directions on 20 wrists of 10 healthy young volunteers, 6 wrists of 5 patients with carpal tunnel syndrome, 6 wrists of 6 patients with nerve lacerations, and one patient with neurofibroma. The MIP post-processing methods employed 2 types of DTI raw images: (1) single-direction and (2) T2-weighted trace. The fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values of the median and ulnar nerves were measured at multiple testing sites. Two radiologists used custom evaluation scales to assess the 3D nerve imaging quality independently.

RESULTS: In both DTI6 and DTI25, nerves in the wrist region could be displayed clearly by the 2 MIP post-processing methods. The FA and ADC values were not significantly different between DTI6 and DTI25, except for the FA values of the ulnar nerves at the level of pisiform bone (p=0.03). As to the imaging quality of each MIP post-processing method, there were no significant differences between DTI6 and DTI25 (p>0.05). The imaging quality of single-direction MIP post-processing was better than that from T2-weighted traces (p<0.05) because of the higher nerve signal intensity.

CONCLUSIONS: Three-dimensional displays of peripheral nerves in the wrist region can be achieved by MIP post-processing for single-direction images and T2-weighted trace images for both DTI6 and DTI25. The FA and ADC values of the median nerves can be accurately measured by using DTI6 data. Adopting 6-direction DTI scan and MIP post-processing is an efficient method for evaluating peripheral nerves.