FIG. 2.

Robotic needling instrument and location of needling in relation to ultrasound transducer (A) and example of ultrasound image with relationship of ultrasound probe and acupuncture needling instrument (B). The location of the acupuncture needle is shown on the right-hand corner of the ultrasound image. The region of interest encompassing the perimuscular connective tissue is delineated by the dashed white lines. The 4 zones used for the detailed analysis of tissue displacement and strain are also indicated, with Zone 1 being furthest away from the needle and Zone 4 including the needle. Arrows indicate the directions of lateral (parallel to the skin) and axial (parallel to the needle) tissue displacement in the ultrasound image plane evaluated in this study. Elevational displacement (not measured in this study) represents displacement in and out of the ultrasound image plane. X- and Y-axis major unit divisions represent 1 cm.