The use of cross-correlation analysis between high-frequency ultrasound images to measure longitudinal median nerve movement

Impaired nerve movement can lead to nerve injury (e.g., carpal tunnel syndr ome). A noninvasive method to measure nerve movement in longitudinal sectio n would enable an extensive analysis of nerve entrapment syndromes. A metho d has been developed using cross-correlation between successive high-freque ncy ultrasound (US) images to measure longitudinal movement of nerve and mu scle. Control "phantom" experiments demonstrated the accuracy and reliabili ty of this method at velocities of 1-10 mm/s. Increasing the frame interval between the compared frames enabled the accurate calculation of slower vel ocities. The correlation algorithm successfully measured relative movement when the US transducer was moved 1-3 mm over the surface of the forearm. Me dian nerve movement was repeatedly measured in the forearm during 30 degree s passive wrist extension in three subjects (range 2.63-4.12 mm) and index finger extension in seven subjects (range 1.59-4.48 mm). Median nerve movem ent values were consistent with those from cadaver studies.