Precision Drug Delivery Positioning in Spinal Procedures Using a Minimally Invasive Device Integrated With Electrodes on Paraylene Film

Accurately determining the position of the needle tip is crucial for enhancing therapeutic effectiveness in spinal procedures. Improper needle placement can lead to serious complications, such as inadvertent drug injection or spinal cord injury. In this study, we propose a hypodermic needle device integrated with electrodes (HIEs) on a high resistivity flexible parylene film, utilizing electrical impedance spectroscopy (EIS). The electrical impedance (EI) of muscle, cerebrospinal fluid (CSF), and spinal cord was measured via experiments using guinea pigs with the HIEs. Statistically significant differences in the real and imaginary components of impedance were observed between CSF and adjacent samples (spinal cord and muscle) in the frequency range of 3.42 kHz to 1 MHz ($\mathrm{p}<0.05$, t-test). Given a real-time measurement in clinical trials, the optimal frequency was indicated by the largest value in the discrimination index between the CSF and adjacent samples. These findings suggest that the HIEs with EIS could enable clinicians to precisely administer drugs or anesthetics in a clinical environment, improving the accuracy and safety of spinal procedures.