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.     

多功能实验动物操作平台

目的介绍一种用于实验动物手术、立体定向给药、PET、核磁共振、CT、电生理检测等操作的多功能实验操作平台。方法采用高强度的有机玻璃板、有机玻璃棒和尼龙棒等工程塑料制作多功能实验操作平台,在该装置的固定下,完成各种实验动物手术、立体定向给药、PET、磁共振成像、CT、电生理检测等操作。结果用该操作平台实验动物得到了稳妥固定、精确定位,并实现各项实验指标的无失真的观测。结论该操作平台设计合理、使用简单、功能多样,是一种良好的实验动物操作平台。     

Brown-Roberts-Wells stereotactic frame modifications to accomplish magnetic resonance imaging guidance in three planes

The Brown-Roberts-Wells (BRW) computer tomography (CT) stereotactic guidance system has been modified to accommodate magnetic resonance imaging (MRI). A smaller head ring, which fits in standard MRI head coils, is constructed of a non-ferromagnetic aluminum ring that is split to prevent eddy currents and anodized to prevent MRI image distortion and resolution degradation. A new localizing device has been designed in a box configuration, which allows BRW stereotactic coordinates to be calculated from coronal and sagittal MRI images, in addition to axial images. The system was tested utilizing a phantom and T1- and T2-weighted images. Using 5-mm MRI scan slices, targets were localized accurately to a 5-mm cube in three combined planes. Optimized calibration of both low field strength (0.3 T) and high field strength (1.5 T) MRI systems is necessary to obtain thin slice (5 mm) images with acceptable image resolution. To date, 10 patients have had MRI stereotactic localization of brain lesions that were better defined by MRI than CT.     

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.     

Computer tomography-controlled stereotactic surgery

In computed tomography (CT)-controlled stereotactic surgery, the coordinate system of the CT scanner is applied to determine the target depth and direction as well as for readjustment of final probe direction. This method can be used for all types of stereotactic surgery for the brain.     

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.     

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.     

MRI contribution to the stereotactic management of cerebral tumours

Of 67 patients with cerebral tumours studied by MRI, 60 underwent stereotactic biopsy for histological diagnosis. The data from MRI were compared with those obtained from the CT scan with regard to the pathological diagnosis. The tumoural nature and extent of a lesion were better revealed by MRI. The single or multiple localization of the process was also seen better by MRI. Moreover, the sagittal-plane views shown by MRI provide much more accurate target placement and probe guiding for an orthogonal stereotactic approach. Finally, a post-biopsy MRI can show the biopsy site in relation to the tumour better.     

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.     

A new apparatus for CT-guided stereotactic surgery

Combining whole-body CT scan with a stereotactic system, the authors have developed and applied clinically an apparatus which readily provides intraoperative CT images, making it possible to confirm the location of the target point and ascertain the intraoperative environment. It takes about 9 s to obtain a CT image. Our purpose is to make stereotactic surgery, a kind of blind surgery, as safe and reliable as a visualized procedure by intraoperative CT scanning. By the method, in which there is very little invasion under local anesthesia, evacuation of deep-seated intracerebral hematomas as well as brain abscesses and also biopsy or brachytherapy of brain tumors in the brain can be done with safety and reliability.     

Computerized tomography-guided stereotactic dentatotomy

The CT stereotactic technique of dentatotomy is described and illustrated with two examples. With this combined technique, ventriculography or pneumencephalography is no longer needed to determine the target point. In addition, due to the direct representation of anatomic structures in the CT, abnormal positions of the dentate nucleus may be taken into consideration in the determination of the target point and approach for the coagulation probe.     

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.     

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.     

Stereotactic interstitial brachytherapy--current concepts and concerns in twenty patients

Recent advances in imaging and stereotactic techniques have resulted in wider application of interstitial brachytherapy (IBT) for brain tumors. The advantages of brachytherapy alone or in combination with teletherapy have been detailed, and may be responsible for increasing survival time. We report the preliminary results of 20 patients who underwent CT stereotactic IBT for malignant brain tumors. Despite both old and recent evidence about the efficacy of IBT, concerns remain about the proper grade neoplasm, the target, the dose, and the timing for treatment. Current usage of IBT should be limited to centers with both stereotactic and radiotherapeutic expertise, and where the risks and benefits are being investigated.     

A new stereotactic instrument for use with computerized tomography and magnetic resonance imaging

The new stereotactic instrument has the advantages of use with computerized tomography (CT) or magnetic resonance imaging (MRI) without special adaptations of instruments, brain targets transferred directly from CT or MRI to apparatus, and use with conventional stereotactic techniques. The apparatus is designed to meet present demands of neurosurgical facilities of good standards and capabilities, encompassing present and future developments towards more efficient and less invasive brain operations.     

An integrated method for reproducible and accurate image-guided stereotactic cranial irradiation of brain tumors using the small animal radiation research platform

Preclinical studies of cranial radiation therapy (RT) using animal brain tumor models have been hampered by technical limitations in the delivery of clinically relevant RT. We established a bioimageable mouse model of glioblastoma multiforme (GBM) and an image-guided radiation delivery system that facilitated precise tumor localization and treatment and which closely resembled clinical RT. Our novel radiation system makes use of magnetic resonance imaging (MRI) and bioluminescent imaging (BLI) to define tumor volumes, computed tomographic (CT) imaging for accurate treatment planning, a novel mouse immobilization system, and precise treatments delivered with the Small Animal Radiation Research Platform. We demonstrated that, in vivo, BLI correlated well with MRI for defining tumor volumes. Our novel restraint system enhanced setup reproducibility and precision, was atraumatic, and minimized artifacts on CT imaging used for treatment planning. We confirmed precise radiation delivery through immunofluorescent analysis of the phosphorylation of histone H2AX in irradiated brains and brain tumors. Assays with an intravenous near-infrared fluorescent probe confirmed that radiation of orthografts increased disruption of the tumor blood-brain barrier (BBB). This integrated model system, which facilitated delivery of precise, reproducible, stereotactic cranial RT in mice and confirmed RT's resultant histologic and BBB changes, may aid future brain tumor research.     

Accuracy of Image Guidance Using Free-Breathing Cone-Beam Computed Tomography for Stereotactic Lung Radiotherapy

Movement of the target object during cone-beam computed tomography (CBCT) leads to motion blurring artifacts. The accuracy of manual image matching in image-guided radiotherapy depends on the image quality. We aimed to assess the accuracy of target position localization using free-breathing CBCT during stereotactic lung radiotherapy. The Vero4DRT linear accelerator device was used for the examinations. Reference point discrepancies between the MV X-ray beam and the CBCT system were calculated using a phantom device with a centrally mounted steel ball. The precision of manual image matching between the CBCT and the averaged intensity (AI) images restructured from four-dimensional CT (4DCT) was estimated with a respiratory motion phantom, as determined in evaluations by five independent operators. Reference point discrepancies between the MV X-ray beam and the CBCT image-guidance systems, categorized as left-right (LR), anterior-posterior (AP), and superior-inferior (SI), were 0.33 ± 0.09, 0.16 ± 0.07, and 0.05 ± 0.04 mm, respectively. The LR, AP, and SI values for residual errors from manual image matching were -0.03 ± 0.22, 0.07 ± 0.25, and -0.79 ± 0.68 mm, respectively. The accuracy of target position localization using the Vero4DRT system in our center was 1.07 ± 1.23 mm (2 SD). This study experimentally demonstrated the sufficient level of geometric accuracy using the free-breathing CBCT and the image-guidance system mounted on the Vero4DRT. However, the inter-observer variation and systematic localization error of image matching substantially affected the overall geometric accuracy. Therefore, when using the free-breathing CBCT images, careful consideration of image matching is especially important.     

Fully Automatic Localization and Segmentation of 3D Vertebral Bodies from CT/MR Images via a Learning-Based Method

In this paper, we address the problems of fully automatic localization and segmentation of 3D vertebral bodies from CT/MR images. We propose a learning-based, unified random forest regression and classification framework to tackle these two problems. More specifically, in the first stage, the localization of 3D vertebral bodies is solved with random forest regression where we aggregate the votes from a set of randomly sampled image patches to get a probability map of the center of a target vertebral body in a given image. The resultant probability map is then further regularized by Hidden Markov Model (HMM) to eliminate potential ambiguity caused by the neighboring vertebral bodies. The output from the first stage allows us to define a region of interest (ROI) for the segmentation step, where we use random forest classification to estimate the likelihood of a voxel in the ROI being foreground or background. The estimated likelihood is combined with the prior probability, which is learned from a set of training data, to get the posterior probability of the voxel. The segmentation of the target vertebral body is then done by a binary thresholding of the estimated probability. We evaluated the present approach on two openly available datasets: 1) 3D T2-weighted spine MR images from 23 patients and 2) 3D spine CT images from 10 patients. Taking manual segmentation as the ground truth (each MR image contains at least 7 vertebral bodies from T11 to L5 and each CT image contains 5 vertebral bodies from L1 to L5), we evaluated the present approach with leave-one-out experiments. Specifically, for the T2-weighted MR images, we achieved for localization a mean error of 1.6 mm, and for segmentation a mean Dice metric of 88.7% and a mean surface distance of 1.5 mm, respectively. For the CT images we achieved for localization a mean error of 1.9 mm, and for segmentation a mean Dice metric of 91.0% and a mean surface distance of 0.9 mm, respectively.     

Somatosensory evoked potentials in the ventrolateral thalamus

Within the target area (VL) used for the stereotactic treatment of parkinsonian tremor and spasmodic torticollis, electrical stimulation as well as recording of somatosensory evoked potential (SEP) was performed. The effects of stimulation in the target area are facilitation of muscle tone showing some degree of somatotopic distribution. The recorded SEPs indicate a projection of an afferent system (probably of muscle afferents) to the target area. We assume that the target area is a relay station involved in the control of muscle tone. The interruption of muscle afferents in combination with the correct somatotopic localization of the lesion is important for the therapeutic efficacy in parkinsonian tremor and spasmodic torticollis.     

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.