Use of the Brown-Roberts-Wells stereotactic frame for functional neurosurgery

The Brown-Roberts-Wells (BRW) stereotactic unit has proven itself to be a highly accurate instrument for biopsying or locating pathologic intracranial lesions based on CT scan information. We utilized the BRW frame to select 18 target sites in 12 patients undergoing functional stereotactic procedures. Two patients had bilateral cingulumotomies, 5 had thalamotomies for movement disorders, and 5 underwent electrode implantations for the treatment of chronic pain. Stereotactic frame settings were determined using a positive contrast ventriculogram, orthogonal radiographs, and a computer program provided with the BRW system. In addition, attempts were made to select targets based on CT scan landmarks alone, and these were compared to those derived using ventriculography. We found the BRW frame to be a satisfactory device for performing functional neurosurgical procedures based on ventriculographic landmarks. Coordinates derived from CT scans were similar to those obtained with ventriculography, but were not accurate enough to permit the use of CT scanning as the sole means of target identification. Although future improvements in imaging techniques and computer software are likely to occur, our experience supports ventriculography as the current method of choice for the precise localization of functional targets with the BRW stereotactic system.     

A method for stereotactic laser microsurgery in the treatment of deep-seated CNS neoplasms

Intracranial tumors are reconstructed in stereotactic space by means of computerized axial tomographic data. The intracranial tumor is operated on with the patient in the stereotactic frame using a carbon dioxide laser to approach the lesion and vaporize it. Ultimately, a gas-filled cavity results which can be monitored on AP and lateral radiographs. Vaporization continues until the cavity produced is superimposable on the coronal and sagittal CT reconstruction. 2 cases treated by this method are presented.     

Real-time three-dimensional graphic reconstructions using Brown-Roberts-Wells frame coordinates in a microcomputer environment

A desktop microcomputer environment that utilizes Brown-Roberts-Wells (BRW) frame coordinates for creation of three-dimensional depiction of operator-defined intracranial structures has been developed. The system allows direct reading of Siemens CT scan images from a floppy disc, structural edge definition, and reconstruction of defined images. The system is used in the operating room to view scans, perform standard BRW stereotactic functions, and create three-dimensional graphics for such tasks as defining tumor margins, conceptualizing positional relationships of intracranial structures, and radiation planning.     

Stereotactic CT scanning for the biopsy of intracranial lesions and functional neurosurgery

This report describes a system for incorporation of stereotactic CT scanning data, stereotactic arteriographic data and a computer-generated stereotactic atlas into a three-dimensional matrix utilizing an operating room computer. 86 patients have undergone computer-assisted stereotactic biopsies of intracranial lesions without mortality or neurologic morbidity. Neuroablative and neuroaugmentative procedures have been performed on 5 patients using the CT stereotactic atlas with good correlation with target points determined by ventriculography and microelectrode recording.     

Technique of stereotactic biopsy of two cranial target employing spherical coordinates to define a single trajectory

A 'spherical coordinate system' has been developed to allow either stereotactic biopsy of two intracranial lesions using a single predetermined trajectory or biopsy of a single lesion through an existing burr hole. By means of the Gildenberg technique, the CT coordinates of the targets (or target and burr hole) are obtained. These are employed in three simple trigonometric equations to give three coordinates-two angles for the probe carrier (theta and alpha) and the radius (T) of a sphere, defined by one target as the center and the other target on the surface. These can be utilized in the Todd-Wells stereotactic frame. This system was evaluated using hollow skulls and crossed 30-gauge wire for phantom targets. The system was tried on ten different target combinations, and eight successful trajectories were obtained to within 3 mm. Two target combinations were inaccessible because of technical limitations of the Todd-Wells frame. This 'spherical coordinate system' can decrease the time to localize multiple targets as well as minimize the number of passes.     

New CT-guided stereotactic apparatus and clinical experience with intracerebral hematomas

The conventional Sugita stereotactic frame has been improved to perform CT-guided stereotactic surgery both in the CT and operating rooms. The development of our instrument and the software of the scanners' computer are presented. Newly designed equipment produced almost no artifacts on the CT image. Using the improved stereotactic frame, we have operated upon 44 intracerebral hematomas in the CT room. More than 80% of the cases had satisfactory results. Two complications were encountered, and 1 patient died from pneumonia. Our initial experience of the pre- and postoperative cerebral blood flow measurement with 133Xe inhalation method and single photon emission CT is described.     

Transposition of target information from the magnetic resonance and computed tomography scan images to conventional X-ray stereotactic space

A technique to apply reconstructed X-ray computed tomography (CT) and magnetic resonance imaging (MRI) for target determination in stereotactic Bragg peak proton beam therapy of intracranial lesions was developed. Twenty-one benign intracranial tumors and vascular abnormalities were managed using this technique. Clinical features of these lesions, as well as targeting problems associated with the MRI and CT image interpretation, are presented.     

Computer-assisted stereotactic biopsy of intracranial lesions

The use of a computer program that allows the integration of stereotactically gathered CT, MRI and digital angiographic data in the planning of a biopsy trajectory is described. This system has been used to perform 447 stereotactic biopsies in 439 patients. Intracranial hemorrhages occurred in three patients; combined morbidity and mortality was less than 1%. Incorporation of angiographic data and visualization of the surgical trajectory enhances the safety and accuracy of stereotactic biopsy of intracranial lesions.     

The role of computed tomographic and digital radiographic techniques in stereotactic procedures for electrode implantation and mapping, and lesion localization

This paper describes a computer-based system for analyzing stereotactic CT scans and angiograms. Simple Plexiglas frames containing metallic marker pellets and rods are affixed to the sides of the frame during CT scanning and angiography. The images of these markers are recognized by the computer program and used to compute the frame coordinate system. Coordinates of a lesion on CT and angiogram images may be readily computed and coordinate sets specified by the operator may be displayed on the imager, along with positions of implanted electrodes and a numerical indication of recorded activity for each site.     

A true 'advanced imaging assisted' skull-mounted stereotactic system

A stereotactic system has been designed based upon a series of interlocking discs secured to the skull with self-tapping screws. Unlike previous skull-mounted systems, this system is a true, advanced imaging based stereotactic device with the capabilities and accuracy of more traditional, frame based devices. It has been used in a range of applications, from simple biopsies to interstitial radiation implant procedures. Well tolerated by the patient, it allows reaccess to the intracranial target without rescanning. It is convenient for the physician to utilize, both mechanically and timewise, is adaptable to MRI, DSA, and conventional X-ray techniques without modification, and is affordable.     

Magnetic resonance imaging stereotaxy: recognition and utilization of the commissures

Magnetic Resonance Imaging (MRI) offers a non-invasive method to visualize the intracerebral structures. Coupled to a compatible stereotactic frame and software, MRI can be used to determine the coordinates of intracranial targets. Coordinates of the anterior commissure, posterior commissure, targets and intercommissural distance were obtained from positive contrast ventriculography and by MRI in 6 patients undergoing stereotactic localization prior to the implantation of stimulating thalamic electrodes for pain control. The correlation of coordinates and measurements obtained with ventriculography and MRI is +/- 1 mm in most measurements, but up to 3 mm in 2 cases. Magnetic resonance stereotaxy allows non-invasive and precise localization of intracerebral targets, but does not yet allow its routine use with confidence. Further understanding of distortion and artifacts and corrections of these is mandatory.     

Validation of frame-based positioning accuracy with cone-beam computed tomography in Gamma Knife Icon radiosurgery

BackgroundFrame based positioning accuracy in Gamma Knife (GK) stereotactic radiosurgery (SRS) is extremely high but removal of a post may be necessary to enable the treatment in selected patients.ObjectiveTo verify the positioning accuracy in clinical scenarios with 4 and 3 posts in patients and phantoms using cone-beam CT (CBCT) of Gamma Knife Icon™.MethodsWe analyzed positioning accuracy for 12 patients with standard 4 post setup using pretreatment CBCT (pre-CBCT) on GK Icon™ and report 4 patients with different clinical scenarios (removal of a post). We performed phantom measurements to verify the frame accuracy via CBCT in different clinical scenarios without the influence of the human patient.ResultsMean frame accuracy for 12 patients with 4 posts was 0.35 mm/0.34 degree. Mean motion during treatment was 0.11 mm/0.04 degree. For two of the clinical scenarios where a post was removed, we found acceptable deviations within 0.66 mm/0.61 degree. For 2 patients, a deviation of 2.94 mm/−3.47 degree and 1.85 mm/−0.74 degree was found and replanning was necessary. Phantom measurements showed good agreement when planning MR/CT was performed with 4 or 3 post. Larger deviations of 0.86 mm/0.88 degree were detected when a post was removed after planning MR/CT.ConclusionThe frame accuracy with 4 posts before and during GK treatments is as high as expected. For clinical situations, where a post is removed after planning-CT/MR, pre-treatment position verification is strongly suggested using stereotactic CBCT or the P-CT/MR should be repeated to avoid possible mistreatments.     

A multipurpose CT-guided stereotactic instrument of simple design

The instrument is based upon a radiolucent ring fixed to the skull by four pins. This locks into a frame for CT scanning from which the x, y and z stereotactic coordinates are derived. The head ring may be locked into a compatible support on the operating table for biopsy. A similar support and localization system is used for rotational radiotherapy. With the current 14 MeV apparatus, fields as small as 2 cm in diameter are available with 90% dosage fall-off in the surrounding 1-cm shell.     

Present and future developments of stereotactic technology

Incorporation of a surgical computer system into stereotactic methodology provides the facility for efficient utilization of the multiple data bases at the disposal of the modern stereotactician. Computed tomography, magnetic resonance imaging, and digital fluoroscopy data gathered in stereotactic conditions are digitized into a stereotactic surgical matrix for surgical planning and interactive surgical procedures. The advantages of this system are illustrated in stereotactic biopsy, interstitial irradiation, and laser resections of intracranial tumors.     

Stereotactic systems and procedures for depth electrode placement: technical aspects

The authors describe the conversion of the Leksell spherical system to that of the orthogonal approach for depth electrode placement, by the addition of relatively simple devices to the main frame. These modifications have created the need for new instrumentation such as teleradiology with laser beam centering and the use of an all-purpose stereotactic chair. The main device used for the orthogonal approach is an instrument and electrode carrier moving on sliding side bars. This system can also take advantage of the newer imaging techniques, such as CT scanning, digital angiography and NMR, by the addition of computer markers which are interchangeable with the frame side bars.     

Stereotactic neurosurgery and computerized tomographic scanning

The marriage of computerized tomographic (CT) scanning and stereotactic surgery opens up new technical possibilities, as it becomes feasible to introduce a probe into any lesion which is identified on a CT scan. The various CT stereotactic techniques are reviewed, and generally involve four variations. The head holder of a standard stereotactic apparatus can be adapted to the CT scanner to interdigitate the coordinates of both devices in a known relationship. Second, some types of CT scanners allow the visualization of the vertical coordinate. Third, a stereotactic microdrive can be incorporated into the scanner. Finally, a simple aiming device can be attached to the patient's head and repeated scans taken as the probe is advanced to the target. Various authors have reported the use of techniques for biopsy, aspiration of cysts or hematomas, insertion of radioisotopes, or as an adjunct to open surgery.     

The Clinical Study of Stereotactic Microsurgery

The objective of this study is to investigate the operative methods and therapeutic effects of stereotactic-guided microsurgical resection of hypertensive cerebral hemorrhage lesions in functional region. 18 cases of intracranial lesions (diameter 1.5–3 cm) were studied using a Leksell-G stereotactic system. Guided by the CT or MR, a small incision was made and the skull was opened with an annular drill. Electrophysiological stimulation was applied along the non-functional areas. 100 patients with cerebral hemorrhage were randomized into two groups of 50 cases each. One of the groups was treated using microsurgery, while the other group was treated using stereotactic technique. A comparative study was carried out between the two treatment methods for hypertensive intracerebral hemorrhage using the recent (1 month) and long-term (6 months) treatment. Using a Leksell-G system for precise positioning of microsurgery, 100 % of the lesion was fully removed. Neurological function was well protected without mortality or neurological deficiency. The use of stereotactic microsurgery for hypertensive intracerebral hemorrhage is successful compared with traditional methods. There is a significant clinical effect on the recovery of neurological function in patients. Stereotactic microsurgical resection of the lesion along with Ribbon treatment of hypertensive cerebral hemorrhage is an accurate, minimally invasive, safe, and effective surgical method.     

Transcranial Doppler ultrasonography: stereotactically guided examinations using magnetic resonance angiography]

The accurate localization of specific intracranial blood vessels is a major difficulty with transcranial Doppler sonography (TCD). It was the purpose of this study to develop a system enabling stereotactic navigation during a TCD examination on the basis of high-resolution three-dimensional magnetic resonance angiographic (MRA) data. During TCD, the examiner is provided--on a computer screen--with a projected view of the respective intracranial vessel anatomy. With the aid of an optoelectronic localization system, the spatial orientation and localization of the US probe is determined in real time, and correlated with the patient's MRA data using a dedicated stereotactic mask. Subsequently, the US beam and the points of insonation are displayed on the screen overlaid on the vessel anatomy. In this way the examiner gains real time control of the localization of the respective intracranial vessel insonated. Points of insonation can be stored and recalled for follow-up examinations. In addition to the successful verification of the system, it was shown that, in comparison with conventional TCD, stereotactic navigation distinctly improves the reproducibility of repeat TCD examinations.     

A new dynamometric technique to measure and locate endocranial structures. Preliminary report

An apparatus for measuring and recording the resistance to penetration of endocranial tissue has been planned and built. The probe carrier, driven by a constant-speed electric motor, is fitted onto a stereotactic head frame which is used to guide the tool to the intended target. The displacement and resistance encountered when the tool penetrates intracranial structures are measured and recorded on an x-y recorder. Preliminary tests performed on calf brain specimens have documented that the apparatus can measure the different consistencies of normal cerebral tissue and suggest a new technique for morphological investigations based on the mechanical consistency of normal and pathological organic tissue. Moreover, the hypothesis of a plastic deformation in cerebral tissue has been confirmed, in that the same apparatus permits one to measure the displacement of tissues caused by the advancement of the surgical tool.     

X-ray and magnetic resonance stereotaxy for functional and nonfunctional neurosurgery

By means of new plastic stereotactic ring and head fixers, stereotactic procedures can be combined with MRI, with stereotactic coordinates obtained from the MRI images. The method was rechecked against CT stereotaxy and shows a good correspondence of the target coordinates. With MRI stereotaxy, structures near bony regions will be more accessible than with CT stereotaxy. Moreover, the MRI procedure seems to have advantages for functional therapy without the necessity of contrast ventriculography.