A frameless, armless navigational system for computer-assisted neurosurgery. Technical note

A simple method for stereotactic microsurgical excision of small, deep-seated cavernous angiomas

Eight patients underwent microsurgical excision of small, deep-seated cavernous angiomas (maximum diameter, 0.9 to 2 cm; distance from cortical surface, 3.5 to 6.5 cm) by the stereotactic implantation of a guide catheter. In all cases, the lesion was quickly localized and completely removed. None of the patients had postoperative neurological deficits. Once the guide catheter has been implanted, the stereotactic headframe can be removed, allowing the unobstructed use of the operating microscope with frames not suitable for open surgery. Target localization is not affected by brain movement, which is inevitable during open surgery. The procedure described here is simple to perform and relatively inexpensive. It requires no specially designed equipment, only a standard stereotactic apparatus, an operating microscope, and the usual microsurgical instruments.

Advances in image-directed neurosurgery: preliminary experience with the ISG Viewing Wand compared with the Leksell G frame

Because of the limited application of frame-based stereotaxy to general neurosurgical procedures, we have carried out a preliminary evaluation of the ISG Viewing Wand, a frameless image-directed surgical system that is based on the rapid reformat and accurate three-dimensional reconstruction capability of parallel processor-based computer technology. We have compared the first 36 cases carried out with the system in the Frenchay Neurosurgery Department with a retrospective analysis of the previous 36 cases carried out using the Leksell G frame. The stereotactic cases were completed over a period of 15 months, representing 2.8% of intracranial procedures. The wand cases were completed in 3 months, 13% of the intracranial practice during that time. The wand was used for 28 supratentorial craniotomies (76%), four infratentorial procedures (11%) and five biopsy procedures (13%). Conventional stereotaxy was not used for posterior fossa or skull base procedures. Supratentorial craniotomy was carried out in nine cases (25%), while the remaining 27 cases involved point source localization within the cranium (75%). The mean preparation time prior to surgery was 65 min for the stereotactic cases and 37 min for the wand cases. We therefore conclude that the indications for frame-based stereotaxy and Viewing Wand use are mutually exclusive. Leksell stereotaxy remains the method of choice for point source localization deep within the cranium. All other procedures requiring an image-directed minimally invasive surgical approach are more appropriately carried out using the Viewing Wand. The system has potential immediate application in supratentorial, skull base and infratentorial tumour surgery, vascular surgery, epilepsy surgery and upper cervical spine surgery.

Magnetic field guided endoscopic dissection through a burr hole may avoid more invasive craniotomies. A preliminary report

The neuroendoscope, coupled with radiofrequency or laser dissecting tools, can effectively resect obstructing membranes, biopsy and debulk tumor, and evacuate hematomas when the pathology is within the ventricular system. This less invasive approach through a burr hole usually avoids craniotomies. When the abnormal condition is within parenchyma or in the presence of opacifying bloody fluid, landmarks are not recognizable and the neurosurgeon quickly becomes disoriented. A more extensive craniotomy or a stereotaxic-guided procedure is then necessary. We describe our preliminary experience with a geographic intracranial navigation system using realtime measurement of electromagnetic field strength in multiple planes to precisely indicate the position of the tip of the endoscope. A transmitting antenna is positioned beneath the patient's head. A 1.5 centimeter cubic antenna receiver is mounted upon a lenscope with instrument channel. The scope is guided into the surgical field after insertion through a burr hole. A square wave pulsed electromagnetic field measurement is made 140 times per second with correction for the earth's magnetic field once per second. Intracranial position data for the dissecting tip in regard to X, Y, Z, pitch, roll and yaw are output to a digitized computer map of the patient's MRI or CT scan. Also displayed on the computer screen is the video image from the endoscope. The neurosurgeon thus has simultaneous realtime geographic and near-field localization as he dissects. Electromagnetic field guided accuracy is within 2.0 mm inside the allowable 24 inch working sphere about the patient's head. Coupled with near-field video precision, accuracy is within 1 mm of recognizable dissection planes.(ABSTRACT TRUNCATED AT 250 WORDS)

Neurosurgical navigation using a noninvasive stereoadapter

A neurosurgical navigation system incorporating a multiarticulated arm and an isocentric stereotaxic mechanism has been developed. The usefulness of the navigation system has been increased by using it in combination with Laitinen's noninvasive, accurately reproducible stereoadapter. Stereotaxic microsurgery and surgical navigation was performed successfully in 30 cases with these systems.

A frameless stereotactic approach to neurosurgical planning based on retrospective patient-image registration. Technical note

A frameless stereotactic device interfacing an electromagnetic three-dimensional (3-D) digitizer to a computer workstation is described. The patient-image coordinate transformation was found by retrospectively registering a digitizer-derived model of the patient's scalp with a magnetic resonance (MR) imaging-derived model of the same surface. This procedure was performed with routine imaging data, eliminating the need to obtain special-purpose MR images with fiducial markers in place. After patient-image fusion was achieved, a hand-held digitizing stylus was moved over the scalp and tracked in real time on cross-sectional and 3-D brain images on the computer screen. This device was used for presurgical localization of lesions in 10 patients with meningeal and superficial brain tumors. The results suggest that the system is accurate enough (typical error range 3 to 8 mm) to enable the surgeon to reduce the craniotomy to one-half the size advisable with conventional qualitative presurgical planning.

Ultrasound-controlled neuronavigator-guided brain surgery

The development of a unique neurosurgical navigator is described and a preliminary series of seven cases of intracerebral lesions approached with the assistance of this neuronavigation system under ultrasound control is presented. The clinical series included five low-grade astrocytomas, one chronic intracerebral hematoma, and one porencephalic cyst. Management procedures included biopsy in all cases, drainage of the hematoma, and endoscopy and fenestration for the cyst. The features of the neuronavigation system are interactive reconstructions of preoperative computerized tomography and magnetic resonance imaging data, corresponding intraoperative ultrasound images, versatility of the interchangeable end-effector instruments, graphic presentation of instruments on the reconstructed images, and voice control of the system. The principle of a common axis in the reconstructed images served to align the navigational pointer, biopsy guide, endoscope guide, ultrasound transducer, and surgical microscope to the brain anatomy. Intraoperative ultrasound imaging helped to verify the accuracy of the neuronavigator and check the results of the procedures. The arm of the neuronavigation system served as a holder for instruments, such as the biopsy guide, endoscope guide, and ultrasound transducer, in addition to functioning as a navigational pointer. Also, the surgical microscope was aligned with the neuronavigator for inspection and biopsy of the hematoma capsule to rule out tumor etiology. Voice control freed the neurosurgeon from manual exercises during start-up and calibration of the system.

Frameless isocentric stereotactic laser beam guide for image-directed microsurgery

We have developed a frameless stereotactic multi-articulated arm suitable for image-directed microsurgery and surgical navigation. The system comprises a frameless isocentric mechanism and a three-dimensional (3 D) digitizer for intra-operative monitoring. Five joints of our multi-articulated arm are equipped with electromagnetic clutches, and the arms are provided with counterbalancing weights to ensure safe, smooth movement. Stereotactic microsurgical procedures were carried out with a laser beam guide mounted at the tip of the isocentric arm. We have used this system in 22 cases to resect tumours or epileptic foci. There were 12 cases of glioma, 5 cases of deep seated benign tumours, 3 cases of multiple metastatic tumours, and 2 cases of temporal lobe epilepsy. Postoperative enhanced CT images indicated total or subtotal resection in all cases. We also have used this system to determine the approach for clipping of a posterior cerebral artery aneurysm in 2 cases. The error of mechanical accuracy of the system was less than 1 mm. We believe that this system will prove useful in image-directed microsurgical procedures.

Neuronavigator-guided cerebral biopsy

Neuronavigators are new dynamic interactive instruments that use on-line computers to orient imaging data to the surgical field and guide the neurosurgeon to his target. We have been working since 1987 on a neuronavigator that serves not only as a precise pointer, but also as a dynamic arm that can be used to hold instruments, such as biopsy guides. The neuronavigator arm consists of six joints with optical encoders and is attached to the Mayfield headholder. The arm is connected to a workstation running customized 3D image graphics software. Special instruments and surgical technique have been developed. Here, we report on early clinical experience with ten biopsy procedures: 4 low-grade and 3 high-grade astrocytomas, one craniopharyngioma and one chronic intracerebral haematoma and intracerebral cyst, both of the latter with surrounding tumour suspect tissue. In all glioma cases serial biopsies were taken from optimal sites under ultrasound imaging control. Eight cases showed representative tumour tissue, while in two cases neoplasia was ruled out. The neuronavigator proved to be versatile, allowing comprehensive imaging data to be adapted to the surgical field.

Computer assisted localizer for planning of surgery and intra-operative orientation

There is discrepancy between the exact representation of anatomical structures and tumours in the CT or MRI scan and the more or less accurate intra-operative localisation methods based mostly upon landmarks of the skull and extracerebral space and visible abnormalities of the cerebral surface. To overcome these problems of exact intra-operative localisation a Computer Assisted Localizer (CAL) is presented which allows precise intra-operative orientation without these aids. It consists of a mechanically articulated arm with six degrees of freedom with a high precision digital incremental and an image processor for 3 D data of the head. MRI and/or CT investigation is done pre-operatively with four reference markers fixed on the patient's head. They are visible on the CT or MRI slices and are used as reference points during surgery for adjustment of the device. The co-ordinates of the digitalizer arm tip are projected into the corresponding axial, sagittal and coronal CT slices so that the system simultaneously presents three orthogonal multiplanar CT reconstructions with a reticule indicating the position of the tip of the arm. As the surgeon directs the arm to the region of interest the corresponding CT slices are displayed on the monitor at a rate of 20 slices/sec determined by the motion of the arm. The accuracy of measurement of the device itself lies within 1 mm. The accuracy is somewhat reduced however by the thickness of CT or MRI slices (routinely 2 mm slices were taken) and by deviations of the reference markers on the skin surface which amount up to 3 mm.(ABSTRACT TRUNCATED AT 250 WORDS)