Animal research stereotactic instrument modified for computed tomographic guidance

While target localization for human stereotactic surgery has been refined by computed tomographic (CT) and magnetic resonance imaging (MRI), stereotaxis in experimental animals has remained dependent upon external cranial landmarks and standardized atlas coordinates. To overcome the limitations and inaccuracies of animal devices using the original Horsley-Clarke method, we modified a standard animal stereotactic instrument in order to make target localization and coordinate determination possible with CT imaging. Although the device can be adapted to any medium-sized animal species, we demonstrate its use with dogs here.     

The impact of computer and imaging technology on stereotactic surgery

Computers, particularly medical imaging techniques, have created a renaissance in stereotactic surgery. Human stereotaxis was primarily developed and performed beginning in the 1940s for functional disorders. Interest waned in the 1960s following the introduction of L-dopa until computer-based three-dimensionally precise tomographic modalities (specifically computed tomography) were introduced beginning in the mid-1970s as a routine diagnostic aid. New image-compatible hardware and instrumentation were introduced along with techniques and associated software for relating points and volumes appearing on these diagnostic images into stereotactic space. This paper reviews the computer and imaging technology that has led to this renaissance and discusses some of the important features of a computer-interactive stereotactic system.     

Single-scan stereotactic tumor biopsy and brachytherapy

Stereotactic tumor biopsy and brachytherapy catheter implantation can be accomplished with targets derived from computed axial tomography and magnetic resonance scans. Computer manipulation of image data allows both diagnostic and therapeutic procedures to be carried out from a single set of scan slices. This eliminates the need for repeat scanning as part of the surgical procedure. Microcomputer technology is sufficiently advanced to handle the images and graphics necessary for stereotactic neurosurgery. A system based on the IBM PC/AT designed for this purpose uses readily available graphics software and custom-designed imaging programs. Direct loading of computed axial or magnetic resonance scan images from magnetic tape can be accomplished. Determination of points, contours and volumes in three-dimensional space allows intraoperative alignment of image data and patient landmarks within the stereotactic head frame using pattern recognition overlays. Three-axis scaling for magnification correction along with rotational and linear data transformations provide the basis for single-scan stereotaxis. Interactive computer graphics integrate image, patient and frame coordinates for target determination. This method eliminates the need to design and fabricate nonmagnetic or radiolucent scanner-compatible devices.     

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.     

Creation of a three-dimensional atlas by interpolation from Schaltenbrand-Bailey's atlas

A 0.5-mm step atlas was interpolated from Schaltenbrand-Bailey's atlas. By serial display of the atlas with the desired rotation on a three-dimensional axis, a three-dimensional atlas was created. The newly created atlas can be used for computer-processed stereotactic data display. Any three-dimensionally located point can be displayed within 0.25 mm distance from the point, and spatial understanding of anatomical structures and stereotactic data is facilitated by the three-dimensional display.     

An applicability study on a CT-guided stereotactic technique for functional neurosurgery

When a CT-guided stereotactic technique for functional neurosurgery is adopted, extremely precise targeting is needed to obtain satisfactory surgical results. In this study the authors have investigated the accuracy of the target points determined by CT-guided techniques and compared with those of conventional roentgenographically controlled stereotactic procedures. Stereotactic surgery, employing the Brown-Roberts-Wells (BRW) system, was performed contemporarily 26 times in 23 patients, that is, 9 times in 8 patients for functional neurosurgery using with the roentgenographic method, and 17 times in 15 patients with the CT-guided method only for intracranial neoplasm biopsy. As a result, there were no problems of accuracy of determining the target points by CT-guided stereotactic surgery with the BRW system. When applying this technique for functional neurosurgery, it should be pointed out that there could be a discrepancy within 2 mm from the conventional target determination.     

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.     

A Statistical Parametric Mapping Toolbox Used for Voxel-Wise Analysis of FDG-PET Images of Rat Brain

Purpose

PET (positron emission tomography) imaging researches of functional metabolism using fluorodeoxyglucose (¹⁸F-FDG) of animal brain are important in neuroscience studies. FDG-PET imaging studies are often performed on groups of rats, so it is desirable to establish an objective voxel-based statistical methodology for group data analysis.

Material and Methods

This study establishes a statistical parametric mapping (SPM) toolbox (plug-ins) named spmratIHEP for voxel-wise analysis of FDG-PET images of rat brain, in which an FDG-PET template and an intracranial mask image of rat brain in Paxinos & Watson space were constructed, and the default settings were modified according to features of rat brain. Compared to previous studies, our constructed rat brain template comprises not only the cerebrum and cerebellum, but also the whole olfactory bulb which made the later cognitive studies much more exhaustive. And with an intracranial mask image in the template space, the brain tissues of individuals could be extracted automatically. Moreover, an atlas space is used for anatomically labeling the functional findings in the Paxinos & Watson space. In order to standardize the template image with the atlas accurately, a synthetic FDG-PET image with six main anatomy structures is constructed from the atlas, which performs as a target image in the co-registration.

Results

The spatial normalization procedure is evaluated, by which the individual rat brain images could be standardized into the Paxinos & Watson space successfully and the intracranial tissues could also be extracted accurately. The practical usability of this toolbox is evaluated using FDG-PET functional images from rats with left side middle cerebral artery occlusion (MCAO) in comparison to normal control rats. And the two-sample t-test statistical result is almost related to the left side MCA.

Conclusion

We established a toolbox of SPM8 named spmratIHEP for voxel-wise analysis of FDG-PET images of rat brain.     

应用MRI预扫描定位提高大鼠脑立体定位术的准确性

目的评价MRI预扫描方法在鼠脑穿刺定位准确性上的作用与价值。材料与方法选取健康雄性SD大鼠18只,随机分为2组,分别为MRI预扫描定位组（9只）,在MR图像指导下进行穿刺注射;以及经典穿刺组（9只）,不采用MR影像学检测定位,严格按照脑立体定位图谱进行穿刺注射。穿刺以通过苍白球中心的鼠脑切面中尾状核区为靶目标,穿刺后采用MRI影像学方法确定穿刺点位置,比较MRI预扫描定位穿刺与经典立体定位穿刺的准确度。结果 MRI预扫描定位组穿刺准确率为88.89%,经典穿刺组穿刺准确率为66.67%;两种方法的穿刺定位差异有显著性（P〈0.05）,MRI预扫描组的穿刺定位准确度明显高于经典穿刺组。结论 MRI预扫描可显著提高鼠脑立体定位穿刺的准确度,是进行立体定位精细穿刺的必要操作。     

Dosimetric comparison of MRI-based HDR brachytherapy and stereotactic radiotherapy in patients with advanced cervical cancer: A virtual brachytherapy study

AimTo evaluate the treatment plans of 3D image-guided brachytherapy (BT) and stereotactic robotic radiotherapy with online image guidance – CyberKnife (CK) in patients with locally advanced cervix cancer.Methods and materialsTen pairs of plans for patients with locally advanced inoperable cervical cancer were created using MR based 3D brachytherapy and stereotaxis CK. The dose that covers 98% of the target volume (HR CTV D98) was taken as a reference and other parameters were compared.ResultsOf the ten studied cases, the dose from D100 GTV was comparable for both devices, on average, the BT GTV D90 was 10–20% higher than for CK. The HR CTV D90 was higher for CK with an average difference of 10–20%, but only fifteen percent of HR CTV (the peripheral part) received a higher dose from CK, while 85% of the target volume received higher doses from BT. We found a significant organ-sparing effect of CK compared to brachytherapy (20–30% lower doses in 0.1 cm³, 1 cm³, and 2 cm³).ConclusionBT remains to be the best method for dose escalation. Due to the significant organ-sparing effect of CK, patients that are not candidates for BT could benefit from stereotaxis more than from classical external beam radiotherapy.     

BrainAligner: 3D registration atlases of Drosophila brains

Analyzing Drosophila melanogaster neural expression patterns in thousands of three-dimensional image stacks of individual brains requires registering them into a canonical framework based on a fiducial reference of neuropil morphology. Given a target brain labeled with predefined landmarks, the BrainAligner program automatically finds the corresponding landmarks in a subject brain and maps it to the coordinate system of the target brain via a deformable warp. Using a neuropil marker (the antibody nc82) as a reference of the brain morphology and a target brain that is itself a statistical average of data for 295 brains, we achieved a registration accuracy of 2 μm on average, permitting assessment of stereotypy, potential connectivity and functional mapping of the adult fruit fly brain. We used BrainAligner to generate an image pattern atlas of 2954 registered brains containing 470 different expression patterns that cover all the major compartments of the fly brain.     

Three-dimensional stereotactic anatomy of the human trigeminal nerve nuclear complex

The trigeminal nuclear complex and its spinal tract extend throughout the greater part of the brain-stem and at medullary levels form the target site for producing stereotactic lesions. This paper describes a method for three-dimensional drawings of this nuclear complex. A stereotactic atlas of the human brain-stem and cerebellar nuclei has formed the data base. The two-dimensional composite transverse sections, at 1-mm intervals have been digitized using an X-Y coordinate plotting microscope. Computer programs have been written to generate drawings of a single transverse hemisection as well as regeneration of the opposite hemibrain-stem section. Specific programs were used to reconstruct serial transverse section outlines and incorporate the trigeminal nuclear complex with and without hidden line removal techniques and colour graphic display facilities. Rotation about the x, y and z axes was possible and permits any view of the reconstructed specimen to be computer-generated. A further program for reconstructing structures as stereopairs is presented.     

Stereotaxic atlas of the guinea pig brainstem

A stereotaxis atlas of the adult guinea pig brainstem is presented. The maps include the structures of medulla, pons, and caudal midbrain region.Translated from Neirofiziologiya, Vol. 25, No. 1, pp. 52–77, January–February, 1993.     

Hypertext atlas of fetal and neonatal pathology

Hypertext atlas of fetal and neonatal pathology is a free resource for pregraduate students of medicine, pathologists and other health professionals dealing with prenatal medicine. The atlas can be found at http://www.muni.cz/atlases. The access is restricted to registered users. Concise texts summarize the gross and microscopic pathology, etiology, and clinical signs of both common and rare fetal and neonatal conditions. The texts are illustrated with over 300 images that are accompanied by short comments. The atlas offers histological pictures of high quality. Virtual microscope interface is used to access the high-resolution histological images. Fetal ultrasound video clips are included. Case studies integrate clinical history, prenatal ultrasonographic examination, gross pathology and histological features. The atlas is available in English (and Czech) and equipped with an active index. The atlas is suitable both for medical students and pathologists as a teaching and reference tool. The atlas is going to be further expanded while keeping the high quality of the images.     

A Flexible Calibration Method Using the Planar Target with a Square Pattern for Line Structured Light Vision System

A flexible calibration approach for line structured light vision system is proposed in this paper. Firstly a camera model is established by transforming the points from the 2D image plane to the world coordinate frame, and the intrinsic parameters of camera can be obtained accurately. Then a novel calibration method for structured light projector is presented by moving a planar target with a square pattern randomly, and the method mainly involves three steps: first, a simple linear model is proposed, by which the plane equation of the target at any orientations can be determined based on the square’s geometry information; second, the pixel coordinates of the light stripe center on the target images are extracted as the control points; finally, the points are projected into the camera coordinate frame with the help of the intrinsic parameters and the plane equations of the target, and the structured light plane can be determined by fitting these three-dimensional points. The experimental data show that the method has good repeatability and accuracy.     

Blind subjects construct conscious mental images of visual scenes encoded in musical form.

Blind (previously sighted) subjects are able to analyse, describe and graphically represent a number of high-contrast visual images translated into musical form de novo. We presented musical transforms of a random assortment of photographic images of objects and urban scenes to such subjects, a few of which depicted architectural and other landmarks that may be useful in navigating a route to a particular destination. Our blind subjects were able to use the sound representation to construct a conscious mental image that was revealed by their ability to depict a visual target by drawing it. We noted the similarity between the way the visual system integrates information from successive fixations to form a representation that is stable across eye movements and the way a succession of image frames (encoded in sound) which depict different portions of the image are integrated to form a seamless mental image. Finally, we discuss the profound resemblance between the way a professional musician carries out a structural analysis of a musical composition in order to relate its structure to the perception of musical form and the strategies used by our blind subjects in isolating structural features that collectively reveal the identity of visual form.     

Anatomical atlas in the context of head and neck radiotherapy and its use to automatic segmentation

In this paper we present a methodology to form an anatomical atlas based on the analysis of dense deformation fields recovered by the Morphons non-rigid registration algorithm. The methodology is based on measuring the bending energy required to register the whole database to a reference, and the atlas is the one image in the database which yields the smallest bending energy when taken as reference. The suitability of our atlas is demonstrated in the context of head and neck radiotherapy through its application to a database with thirty-one computed tomography (CT) images of the head and neck region. In head and neck radiotherapy, CT is the most frequently used modality for the segmentation of organs at risk and clinical target volumes. One challenge brought by the use of CT images is the presence of important artifacts caused by dental implants. The presence of such artifacts hinders the use of intensity averages, thus severely limiting the application of most atlas building techniques described in the literature in this context. The results presented in the paper show that our bending energy model faithfully represents the shape variability of patients in the head and neck region; they also show its good performance in segmentation of volumes of interest in radiotherapy. Moreover, when compared to other atlases of similar performance in automatic segmentation, our atlas presents the desirable feature of not being blurred after intensity averaging.     

Automated stereotactic positioning system

An automated stereotactic machine has been interfaced to a surgical computer to complete a totally interactive surgical system capable of locating tumor volumes. Stepper motors, activated by the host computer, drive a three-dimensional slide to position the patient's head with respect to a fixed arc, locating the surgical target. Linear encoders on each axis create a closed-loop positioning system and a digital display for visual inspection of the slide's position. The 160-mm arc directs all instrumentation to its isocenter, regardless of the two angular settings, providing maximum freedom in selecting a safe trajectory to the target. Phantom test points compatible with computerized tomographic and magnetic resonance imaging were repeatedly scanned to determine the overall system accuracy, which approached 0.6 mm, depending on the spatial resolution of the image. This stereotactic device may be used to perform stereotactic laser craniotomies, biopsies, 192Ir implants for interstitial radiation, third ventriculostomies and functional procedures.     

A Diffusion-Tensor-Based White Matter Atlas for Rhesus Macaques

Atlases of key white matter (WM) structures in humans are widely available, and are very useful for region of interest (ROI)-based analyses of WM properties. There are histology-based atlases of cortical areas in the rhesus macaque, but none currently of specific WM structures. Since ROI-based analysis of WM pathways is also useful in studies using rhesus diffusion tensor imaging (DTI) data, we have here created an atlas based on a publicly available DTI-based template of young rhesus macaques. The atlas was constructed to mimic the structure of an existing human atlas that is widely used, making results translatable between species. Parcellations were carefully hand-drawn on a principle-direction color-coded fractional anisotropy image of the population template. The resulting atlas can be used as a reference to which registration of individual rhesus data can be performed for the purpose of white-matter parcellation. Alternatively, specific ROIs from the atlas may be warped into individual space to be used in ROI-based group analyses. This atlas will be made publicly available so that it may be used as a resource for DTI studies of rhesus macaques.     

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.