A method for correcting inherent distortions in a CT or MRI imaging process, or distortions arising from excessive patient movement during the scan by means of a registration device inserted into the mouth of the patient at the time the scan is being performed. The registration device incorporates a set of fiducial markers disposed in a predetermined three-dimensional pattern. The exact positions of the fiducial markers are known with respect to each other, thus providing a three-dimensional reference against which the resulting images can be compared. Additionally, a method whereby three-dimensional CT or MRI images taken prior to an operation, are accurately registered and integrated with real-time tracking positional data of the patient's body part and instruments operating thereon. Application is described for the drilling of a patient's jaw for the placement of dental implants.