Dynamic Analysis of Ultrasound Images of the Median Nerve Using Particle Image Velocimetry.

Carpal tunnel syndrome (CTS) diagnosis is typically confirmed through electrophysiologic studies and ultrasound (US) imaging. Recent studies have suggested that median nerve gliding is reduced in patients with CTS. This study employed particle image velocimetry (PIV) to analyze median nerve dynamics. Ultrasound movies were captured during finger flexion and extension for 20 healthy volunteers (control group) and 20 CTS patients (CTS group). These movies were then analyzed using the PIV method. Within a 10 x 10 mm² region of interest (ROI) that included the median nerve and flexor tendon, the velocity magnitude and vector direction of movement were examined using PIV software. The maximum and mean velocity magnitudes were compared between the two groups using the Mann-Whitney U test. The maximum velocity in the ROI was significantly lower in the CTS group (9.3 ± 3.0 mm/s) than in the control group (11.5 ± 3.4 mm/s). The mean velocity was also significantly lower in the CTS group (1.7 ± 0.3 mm/s) than in the control group (2.5 ± 0.7 mm/s). Regarding motor properties, transverse motor velocity was significantly lower in CTS patients than in controls, while vertical movement showed no significant difference between the two groups. This study applied the PIV method to US images for dynamic analysis of the median nerve, revealing reduced gliding of the median nerve and flexor tendon in CTS patients, particularly in transverse movements. The application of dynamic analysis using the PIV method has potential for use in diagnosis and rehabilitation of CTS.