Abstract: A surgical system includes a navigation system with a localizer and a surgical instrument having a body, a shaft with a distal tip for contacting material associated with an anatomy, and a tracking device detectable by the localizer. The shaft houses first and second conductors, insulated from each other, extending to the distal tip. One or more controllers are configured to transmit a variable-frequency signal across the conductors, measure impedance of the material based on the signal, and characterize the material type based on the measured impedance.

Abstract: A transcutaneous energy transfer system with subcutaneous non coupled coils is used to transmit power and signals to an implanted biological support device or sensor, such as a flow sensor for measuring relatively low flow rates, such as hydrocephalic shunt flow. The flow sensor is configured to convert a shear wave generated by a transducer to a longitudinal wave at the interface of a signal pathway and the flow, wherein the longitudinal wave travels parallel to the flow and exits a flow channel to convert to a shear wave which intersects a second transducer. The transcutaneous energy transfer employs a pair of inductive coupling coils, wherein the coils are disposed in zero coupling orientation which can include a perpendicular orientation of corresponding coil axes.