Intraoperative imaging: evolutions, options, and practical applications.

“Stereotactic procedures involve two frightened people separated by a needle. ”—Attributed to Robert Selker, M.D. Image guidance is being increasingly used for brain operations in today’s era. This includes craniotomy for most nontrauma indications, conventional stereotactic surgery, functional surgery, and radiosurgery.27 The personal interest of the senior author (LDL) in this field began at the time that he started his residency in 1975. The first computed tomography (CT) scanner, an Electric & Musical Industries (EMI) device with a water bag, arrived on July 1, 1975, his first day as a resident. This scanner required the use of a water-filled tank with a preshaped rubber “head cap” at the front, which enclosed the patient’s head. This tank was used to reduce the dynamic range of the radiation reaching the detectors. This first CT scanner was developed by Hounsfield in his laboratory at EMI and took several hours to acquire the raw data for a single scan or “slice” and took days to reconstruct a single image from these raw data. The recognition of the value of computer-based imaging became immediately apparent.39 During the subsequent years of training, the senior author had an opportunity to work with an innovative neuroradiologist, Arthur Rosenbaum, M.D., and an engineer, John Perry, Ph.D., who then headed the imaging division of Pfizer Medical Instruments. Together, we developed an imageguided stereotactic system using the now well-known N-localizer technology. This elegant solution was proposed by Perry et al.41 and Rosenbaum et al.44 independently and virtually simultaneously as publications from Brown2 and Roberts and Brown43 of Utah. The adaption of CT for stereotaxic operations required the transformation of the coordinates of the target point from the CT image space into the stereotaxic frame space. On each slice, the XY coordinates of the nine points representing the slices of the edges and diagonals of the localizer define the plane of the slice with regard to the plane of the head ring. During the interval of 1979 to 1980, 13 stereotactic procedures were performed in a diagnostic scanner at our hospital. An opportunity presented itself for the senior author to undergo additional training focused in stereotactic and functional neurosurgery at the Karolinska Institute. Under the auspices of the American Association of Neurological Surgeons Van Wagenen Fellowship, the senior author spent one year in Stockholm studying under the tutelage of Professors Erik-Olof Backlund and Lars Leksell. During this interval, the newly redesigned Leksell CTcompatible stereotactic head frame20 was used for dedicated brain biopsies under the direction of its inventor, Lars Leksell (Fig. 9.1). This fellowship included experience with stereotactic surgery, gamma knife radiosurgery, and functional surgery. On returning to Pittsburgh in 1981, the senior author began a quest to obtain a dedicated CT scanner-equipped operating room at a time when the regional health systems agency had allocated two diagnostic CT scanners to the entire city of Pittsburgh. After a number of meetings, we obtained a certificate of need to install a dedicated GE 8800 scanner (General Electric, Fairfield, CT) specifically for therapeutic neurosurgical purposes (Fig. 9.2). We built a new operating room and began our first series of stereotactic procedures.3,6,19,21,28,29,31,33,35,37 The scanner was updated to a GE 9800 in 1991. Stereotactic and functional neurosurgery had gone through a period of relative inactivity during the 1960s and 1970s at most U.S. centers because of the development of more effective antiparkinsonian medications. This fact also led to a decline in the training of neurosurgeons who could perform functional neurosurgery. Part two of our plan for developing image-guided neurosurgery was the introduction of the Leksell gamma knife into the U.S.30 Intense planning for this project began in 1982. After involving the dedication and talents of many people, we were able to introduce this groundbreaking technology into North America. The first 201 source cobalt-60 gamma knife was installed at the University of Pittsburgh, Presbyterian–University Hospital, and the first patient was treated in August 1987.25,26,30 By August 2008, 9300 patients had undergone gamma knife radiosurgery at our center. There are a number of basic tenets necessary to introduce new technologies into the neurosurgical mainstream. The first principle is that the technology should be simple and practical. It must assist the surgeon to perform the operation, Copyright © 2008 by The Congress of Neurological Surgeons 0148-703/08/5501-0076