A system for monitoring a position of a medical instrument with respect to a patient's body, including a medical instrument, a reference mount attachable to the patient's body for movement with the patient's body, and an electromagnetic unit for association with the reference mount and the medical instrument for monitoring movement of the medical instrument relative to the reference mount. The electromagnetic unit includes a first member attachable to the patient's body and a second member attachable to the medical instrument. The first and second members communicate by electromagnetic radiation.
