Electrical impedance of an ultrasonic needle device as an indicator of interstitial needle tip position

Ultrasound-guided percutaneous needle procedures, commonly employed in regional anaesthesia and tissue biopsy, face challenges in accurately localizing the needle tip. This study explores the potential of using real-time electrical impedance measurements from an ultrasonic needle device as an indicator of the needle tip location, with reference to insertion force. The device utilizes a Langevin piezoelectric ultrasound transducer to actuate a general anaesthesia needle, while an adaptive control system provides impedance measurements in real time. Gelatin phantoms with varying concentrations, a skin-mimicking layer made of silicone, and a medical plastic gloves layer were used to create single- and multi-layer testing objects. The results suggest that the impedance magnitude is comparable to the force in identifying key events during needle insertions, such as puncturing and layer transitions. Furthermore, impedance proves particularly reliable when the needle is stationary, indicating a strong potential as a valuable feedback signal for enhancing percutaneous needle procedures.