Stereotactic biopsies guided by an optical navigation system: technique and clinical experience.

Frame-based stereotactic biopsies are time-consuming procedures making necessary head fixation in a ring, explicit coordinate calculation and setting of the parameters. Frameless systems make many of these intermediate steps unnecessary, impose less mechanical restrictions regarding access to the lesions, and with slight modifications can be used to perform stereotactic biopsies. A special adaptation designed to fix the holder and the biopsy instrument is described. The neuronavigation optical tracking system of Radionics was used. CT scans were performed with 6 skin markers. Calibration was performed after head fixation in the Mayfield clamp. Mean calibration error was 2.19 +/- 0.81 mm. The light-emitting diode holder of the pointer was fixed into 2 Leila arms and moved under visual control based on CT images. The target point was selected, Leila arms fixed and a burr hole performed. The cannula was introduced to the target, being fitted with a depth stop in a length identical to that of the pointer on the screen. If necessary a second trajectory was easily selected. 49 patients underwent a frameless stereotactic biopsy. All targets except seven were superficial or in the white matter. In selected cases the biopsies were taken from deep-seated lesions. A histological diagnosis was obtained in 100 % of the cases. Four cases deteriorated postoperatively, two of these related to intratumoral bleeding. Navigation is a simple and effective method to perform biopsies of superficial and relatively large lesions. Frame-based procedures are restricted to brainstem tumors and lesions less than 1.5 cm in diameter.

Frameless neuronavigation applied to endoscopic neurosurgery.

OBJECTIVE: We retrospectively analyzed the indications, surgical techniques, and applicability of frameless neuronavigation to endoscopic procedures in a heterogeneous group of 15 patients. MATERIAL AND METHODS: In 8 patients indications for surgery were cystic lesions, in 3 patients intraventricular tumors, and in 4 patients occlusive hydrocephalus. The mean age was 39 years (range 9-76 years). The follow-up period ranged from 5-24 months (mean 10 months). Frameless neuronavigation was accomplished with the "operating arm system" in 10 cases and with the "optical tracking system" in 5 cases (RADIONICS, Burlington, USA). RESULTS: In all 15 cases, neuronavigation sufficiently provided anatomical orientation, preoperative planning, and intraoperative realization of the approach. The calculated mean calibration error was 2.1 mm. There have been no permanent morbidities and no mortalities related to the use of endoscopes and neuronavigation. CONCLUSION: In endoscopic neurosurgery, frameless neuronavigation is a useful tool in planning and realizing the approach and improving intraoperative orientation in selected cases. Indications are small or hidden lesions, impaired visual conditions, abnormal anatomy, and narrow ventricles. Endoscopic procedures include fenestration and resection of intraventricular or intraparenchymal cysts, biopsy of intraventricular tumors, and third ventriculostomy in selected cases.

Basic principles and clinical applications of neuronavigation and intraoperative computed tomography.

Computed tomography (CT) images in combination with a navigation device enable three-dimensional (3-D) localization of intracranial lesions. Furthermore, CT scanning can be adapted for intraoperative application to actualize the image data and to check the anatomical situation during the operation. Frameless navigation was used in 100 patients. The procedure was performed in 46 cases with an optical navigation system, in 38 cases with a sensory arm, and in 16 cases with a navigated microscope. Six skin markers were used for registration. Mean fiducial registration error was 2.18 mm with a standard deviation of 1.03 mm. The indication for navigation was tumor localization and planning of the craniotomy in 81 cases, stereotactic biopsy in eight cases, and endoscopic procedures in 11 cases. Technical problems with the navigation system were observed in nine cases. In two additional cases the tumor was not found by navigation. All eight biopsy cases were successful, and histologically relevant specimens were obtained without complications. Navigation was helpful in 11 endoscopic cases for choosing an optimal trajectory through the foramen of Monro or for connecting multiple intraventricular cysts. For intraoperative CT imaging, the mobile Philips Tomoscan M was adapted to the needs of the operating environment. The mobile CT was used in 78 cases in the operating room: 16 patients who underwent a stereotactic procedure had only preoperative CT scans, 36 patients had an intraoperative CT during tumor surgery, and 26 patients during the test period of the device had only a postoperative CT investigation. In 10 cases (28%) of the intraoperative group the remaining tumor tissue could be demonstrated on the CT scans. The tumor remnants that were not visible in the microscopical surgical field were subsequently removed. According to our results, intraoperative navigation seems superior for the localization of intracranial lesions and intraoperative CT is more useful when considering the radicality of tumor removal.

Teleconsultation: a new neurosurgical image transfer system for daily routine and emergency cases--a four-year study.

In January 1991, an image transfer unit was developed and installed in the neurosurgical department of the University in Mainz. The system provides an image transfer of patient data via fibreoptic cable networks (VBN), ISDN, and public telephone line. In the following 4 years, 432 consultations were recorded. Nine departments were linked within this system. They provided an emergency out-patient department for primary treatment and radiology. The lack of a neurosurgical department in these clinics was made up for by the image transfer system. In these rural medical departments, teleconsultation improves the care of daily routine neurosurgical cases, as well as in emergency cases. There is also a decrease of costs due to teleconsultation. The image transfer via simple public telephone line was sufficient.