The most precise form of stereotaxis makes use of a headframe that is rigidly affixed to the patient's head. The headframe system in use at NYU is the COMPASS system. This system was designed to facilitate resection of brain tumors and offers several advantages over other stereotactic systems. This headframe is placed during a brief procedure, usually on the morning of surgery or one day before. The patient then undergoes imaging with the headframe in place. This can consist of MRI and/or CT scanning and sometimes a cerebral angiogram. Information from these studies is then transferred to the stereotactic computer and reconstructed into a three dimensional database. The surgeon then defines the tumor volume by outlining the borders of the tumor on individual images. The computer constructs a three dimensional volume from these contours, which can then be viewed from any trajectory. An optimal trajectory can then be selected that provides access to the tumor while avoiding critical blood vessels and brain structures.

During surgery, the COMPASS system provides visual guidance to the surgeon, helping to define the borders of the tumor and the adjacent brain tissue. This is especially useful for the resection of primary tumors such as gliomas. For deep tumors located in the thalamus, basal ganglia, or ventricular system (the fluid chambers of the brain) the COMPASS system can be used with a cylindrical retractor that provides a precise access through the overlying brain tissue. This minimizes the risk of injury to vital structures and makes it possible to safely locate and remove tumors that would otherwise be difficult or impossible to resect.

This type of surgery usually requires a hospital stay of approximately 3 days. The patient is usually admitted on the morning of surgery. Headframe placement is the first part of the procedure. This takes about 15 minutes. The patient is briefly anesthetized during headframe placement to minimize discomfort. Following headframe placement, the patient undergoes the appropriate diagnostic procedures; MRI, CT, and sometimes cerebral angiography. Following these procedures, the patient returns to the operating room and undergoes the surgical procedure. In routine cases, the patient usually spends one night in the ICU. A postoperative scan is obtained and the patient is moved to a private or semiprivate room on the day following surgery. The patient is usually discharged home on the third postoperative day.