There are many reports of the use of stereotactic systems for mass lesion localization at craniotomy. However, such frame systems have not attained universal usage due to the increased time and effort necessary in their use. In most centers, a frame must be applied to the head, the patient transferred to a radiology suite where CT or MR imaging is performed, the patient must be taken back to the operating room, and then localization performed using stereotactic tools. Many feel that the frame restricts access to placement of the skin incision and bone flap. Despite such limitations, and the availability of an intraoperative CT scan at the University of Pittsburgh, we have used stereotactic frame guidance at craniotomy since 1981 and found it to be user-friendly and accurate.
Many surgeons use intraoperative ultrasound to localize lesions deep to the brain surface.
If accuracy of one millimeter is paramount to be able to localize the lesion and plan a trajectory, then a stereotactic frame provides the best possible choice. Such an instance might be the resection of a deeply-located small mycotic aneurysm. We continue to use stereotactic frames for precise guidance to the microsurgical resection of colloid cysts. If however, guidance is sought in the resection of a 3 cm malignant brain tumor, where accuracy in the 2 - 4 mm range would be quite suitable, then a frameless system is appropriate and helpful. With improvements in computer technology, and the coming increased availability of frameless stereotactic systems, we believe that eventually all craniotomies within five years will be performed using intra-operative image guidance.