A-mode ultrasonic detection of subcutaneous fiducial markers for image — Physical space registration

Fiducial markers are reference points used in the registration of multiple image volumes, as well as in the registration of image space with physical (patient) space. As applied to interactive, image-guided surgery systems, the registration of image space with physical space allows the current surgical location to be indicated on a computer display of preoperative images. This additional guidance information is particularly valuable in surgery within the brain. To effect accurate space registration for computer assisted neurosurgery, we propose the use of permanent fiducial markers, implanted into the surface of the skull. This paper presents a technique based on characteristics of the reflected A-mode ultrasound waveform for detecting marker location transcutaneously.