Abstract: A method, and an apparatus to perform the method, of determining a location of a medical instrument in a patient during a medical procedure, the method including connecting at least a portion of the medical instrument to a first body region of the patient, propagating a plurality of signals at different frequencies along a conductive path of the medical instrument, measuring one or more feedback parameters corresponding to each of the plurality of signals at the first body region, determining an operational frequency from the different frequencies according to a comparison of the one or more feedback parameters, propagating a signal having the operational frequency along the conductive path as the medical instrument penetrates the body of the patient during the medical procedure, and measuring the one or more feedback parameters corresponding to the operational frequency to determine a penetration location of the medical instrument in the body of the patient.