Frameless Stereotaxy – Indications, Techniques and Results

Abstract

Open craniotomy remains the main stay of diagnostic and therapeutic management of brain tumor. Intraoperative localization may be difficult due to the fact that some lesions, which might appear clearly on MR or CT, could be completely indistinguishable from normal brain when examined through a microscope, hence the use of the stereotactic head frame. The disadvantages of this technique are the patient’s discomfort, inconvenience of travelling between OT and imaging department with head ring on, the difficulty in calculating the co-ordinates and the fact that introduction of Biopsy needle remains a blind procedure. At the 1991 American Association of Neurological Surgeons annual meeting, a new surgical navigational method initially called Frameless Stereotaxy (interactive image-guided surgery) came into being. Intraoperative Localization Device (ILD) include linked and unlinked devices. Linked devices include stereotactic frames, active robotic arms (PUMA Industrial Robot, the Zeiss MKM microscope) and passive localization arms (the OAS system) and intraoperative tomographic scanners. A number of steps are taken in order to ensure correct functioning of these systems. • Patient selection • Fiducial placement • Imaging • Data transport • Presurgical viewing • Identification and registration of markers • Surgical planning and intraoperative navigation We are using Operating Arm System (OTS) designed by Radionics, Inc. for cases that require precise localization and Intraoperative guidance. OTS consists of a workstation connected to a probe with optical digitisers, which interacts with a camera which tracks, the movement of the probe in 3 dimension. We use four stick-ons to calibrate the system and two other as target points. The author’s personal experience has been with 70 cases over the last six years, which shall be presented.