Microcomputer stereotactic atlas

A stereotactic atlas to determine thalamic target sites has been incorporated into a microcomputer. Variability studies of the thalamus with mean and standard deviations of nuclear borders are depicted graphically for overlay onto operative images. Internal landmarks traditionally used to reference target points for functional stereotaxis may be determined by conventional ventriculography or derived from magnetic resonance scans. Modeling of polyline vertices established from gray scale contour mapping and atlas reconstructions further enhance the spatial understanding of relationships to midline structures. Computer integration of anatomic reference points, graphically depicted images and stereotactic atlas data into head frame coordinates can be accomplished. This method is consistent with established stereotactic techniques and allows the visual conceptualization of imaged and graphic data for functional stereotaxis.     

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.     

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.     

Construction of a confocal microscope for real-time x-y and x-z imaging

We describe the construction of a simple 'real-time' laser-scanning confocal microscope, and illustrate its use for rapid imaging of elementary intracellular calcium signaling events. A resonant scanning galvanometer (8 kHz) allows x-y frame acquisition rates of 15 or 30 Hz, and the use of mirrors to scan the laser beam permits use of true, pin-hole confocal detection to provide diffraction-limited spatial resolution. Furthermore, use of a piezoelectric device to rapidly focus the objective lens allows axial (x-z) images to be obtained from thick specimens at similar frame rates. A computer with image acquisition and graphics cards converts the output from the microscope to a standard video signal, which can then be recorded on videotape and analyzed by regular image processing systems. The system is largely made from commercially available components and requires little custom construction of mechanical parts or electronic circuitry. It costs only a small fraction of that of comparable commercial instruments, yet offers greater versatility and similar or better performance.     

An automatic matching technique for patient alignment

An automatic system of patient alignment is required in order to monitor changes that occur in the period between magnetic resonance scans. For each scan of the patient a prime requisite is to register the images with respect to each other. The orthogonal relationship between the sagittal and transverse images should, in principle, identify a single common line at the intersection of the two image planes. The basis of the comparison requires spatial registration of the two images to correct for the probable translational and rotational tilts as well as for the geometrical and intensity distortions. This paper describes a number of automatic techniques which compare, pixel-by-pixel, first two synthetic images, and then their application to real images obtained separately from the same head and neck object field. The robustness, computational cost and effectiveness of the techniques presented are discussed, and computed results on real data for the most promising technique based on the Ratio Absolute Difference algorithm are presented.     

Clinical examination or whole-body magnetic resonance imaging: the Holy Grail of spondyloarthritis imaging

Whole-body magnetic resonance imaging allows acquisition of diagnostic images in the shortest scan time, leading to better patient compliance and artifact-free images. Methods of clinical examination of the anterior chest wall joints vary between physician groups and consideration of the rules of rib motion is suggested. The type of joint and its synovial lining may also aid imaging/clinical correlation. This well-written study by experts in the field with a standardized design and methodology allows good scientific analysis and suggests the advantages of whole-body magnetic resonance imaging in anterior chest wall imaging. Selection of clinical examination criteria and specific joints may have had an influence on the study results and the lack of association reported.     

A study to determine the impact of IMPT optimization techniques on prostate synthetic CT image sets dose comparison against CT image sets

BackgroundThe objective of this study is to determine the impact of intensity modulated proton therapty (IMPT) optimization techniques on the proton dose comparison of commercially available magnetic resonance for calculating attenuation (MRCA T) images, a synthetic computed tomography CT (sCT) based on magnetic resonance imaging (MRI) scan against the CT images and find out the optimization technique which creates plans with the least dose differences against the regular CT image sets.Material and methodsRegular CT data sets and sCT image sets were obtained for 10 prostate patients for the study. Six plans were created using six distinct IMPT optimization techniques including multi-field optimization (MFO), single field uniform dose (SFUD) optimization, and robust optimization (RO) in CT image sets. These plans were copied to MRCA T, sCT datasets and doses were computed. Doses from CT and MRCA T data sets were compared for each patient using 2D dose distribution display, dose volume histograms (DVH), homogeneity index (HI), conformation number (CN) and 3D gamma analysis. A two tailed t-test was conducted on HI and CN with 5% significance level with a null hypothesis for CT and sCT image sets.ResultsAnalysis of ten CT and sCT image sets with different IMPT optimization techniques shows that a few of the techniques show significant differences between plans for a few evaluation parameters. Isodose lines, DVH, HI, CN and t-test analysis shows that robust optimizations with 2% range error incorporated results in plans, when re-computed in sCT image sets results in the least dose differences against CT plans compared to other optimization techniques. The second best optimization technique with the least dose differences was robust optimization with 5% range error.ConclusionThis study affirmatively demonstrates the impact of IMPT optimization techniques on synthetic CT image sets dose comparison against CT images and determines the robust optimization with 2% range error as the optimization technique which gives the least dose difference when compared to CT plans.     

A method for measurement of joint kinematics in vivo by registration of 3-D geometric models with cine phase contrast magnetic resonance imaging data

A new method is presented for measuring joint kinematics by optimally matching modeled trajectories of geometric surface models of bones with cine phase contrast (cine-PC) magnetic resonance imaging data. The incorporation of the geometric bone models (GBMs) allows computation of kinematics based on coordinate systems placed relative to full 3-D anatomy, as well as quantification of changes in articular contact locations and relative velocities during dynamic motion. These capabilities are additional to those of cine-PC based techniques that have been used previously to measure joint kinematics during activity. Cine-PC magnitude and velocity data are collected on a fixed image plane prescribed through a repetitively moved skeletal joint. The intersection of each GBM with a simulated image plane is calculated as the model moves along a computed trajectory, and cine-PC velocity data are sampled from the regions of the velocity images within the area of this intersection. From the sampled velocity data, the instantaneous linear and angular velocities of a coordinate system fixed to the GBM are estimated, and integration of the linear and angular velocities is used to predict updated trajectories. A moving validation phantom that produces motions and velocity data similar to those observed in an experiment on human knee kinematics was designed. This phantom was used to assess cine-PC rigid body tracking performance by comparing the kinematics of the phantom measured by this method to similar measurements made using a magnetic tracking system. Average differences between the two methods were measured as 2.82 mm rms for anterior/posterior tibial position, and 2.63 deg rms for axial rotation. An intertrial repeatability study of human knee kinematics using the new method produced rms differences in anterior/posterior tibial position and axial rotation of 1.44 mm and 2.35 deg. The performance of the method is concluded to be sufficient for the effective study of kinematic changes caused to knees by soft tissue injuries.     

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.     

Computer-interactive stereotactic resection of deep-seated and centrally located intraaxial brain lesions

The carbon dioxide laser has been incorporated into a computer-interactive stereotactic system for precision resection of deep-seated intraaxial neoplasma defined by stereotactic computed tomography and magnetic resonance imaging. One hundred and ninety-seven procedures were performed on 191 patients having deep-seated lesions. Postoperative results have been satisfactory as regards the postoperative condition of the patient in consideration of the completeness of tumor removal achieved.     

Zero echo time MRI-only treatment planning for radiation therapy of brain tumors after resection

Using magnetic resonance imaging (MRI) as the sole imaging modality for patient modeling in radiation therapy (RT) is a challenging task due to the need to derive electron density information from MRI and construct a so-called pseudo-computed tomography (pCT) image. We have previously published a new method to derive pCT images from head T1-weighted (T1-w) MR images using a single-atlas propagation scheme followed by a post hoc correction of the mapped CT numbers using local intensity information. The purpose of this study was to investigate the performance of our method with head zero echo time (ZTE) MR images. To evaluate results, the mean absolute error in bins of 20 HU was calculated with respect to the true planning CT scan of the patient. We demonstrated that applying our method using ZTE MR images instead of T1-w improved the correctness of the pCT in case of bone resection surgery prior to RT (that is, an example of large anatomical difference between the atlas and the patient).     

单排CT轴位螺旋扫描联合冠状面重组技术对鼻腔鼻窦检查的意义

目的：研究在单排CT轴位螺旋扫描联合多层面重组技术重建冠状面影像诊断鼻腔疾病,评价其诊断价值和可行性。方法：对2012年1月-2013年3月我院耳鼻咽喉科进行单排CT轴位螺旋扫描的患者,共219例,对这些患者加做冠状位扫描,比较重建后的影像资料与直接冠状位扫描的图像的分辨率情况,并评估重建质量及运用价值。,结果：单排CT轴位螺旋扫描后冠状面重组的图像：边界清楚、完整,数据无丢失。利用重组技术后重建的结构清晰、连续,能够真实地反映鼻腔、鼻窦及病变结构的实际情况。但分辨率较直接冠状位平扫的患者稍差。结论：单排CT轴位螺旋扫描后冠状面重组的图像,虽然分辨率不如直接冠状位扫描图像高,但与解剖结构、原图像等相结合仍能分辨出病变情况,基本可以满足诊断要求和临床需要。     

Fast space-filling molecular graphics using dynamic partitioning among parallel processors

We present a novel algorithm for the efficient generation of high-quality space-filling molecular graphics that is particularly appropriate for the creation of the large number of images needed in the animation of molecular dynamics. Each atom of the molecule is represented by a sphere of an appropriate radius, and the image of the sphere is constructed pixel-by-pixel using a generalization of the lighting model proposed by Porter (Comp. Graphics 1978, 12, 282). The edges of the spheres are antialiased, and intersections between spheres are handled through a simple blending algorithm that provides very smooth edges. We have implemented this algorithm on a multiprocessor computer using a procedure that dynamically repartitions the effort among the processors based on the CPU time used by each processor to create the previous image. This dynamic reallocation among processors automatically maximizes efficiency in the face of both the changing nature of the image from frame to frame and the shifting demands of the other programs running simultaneously on the same processors. We present data showing the efficiency of this multiprocessing algorithm as the number of processors is increased. The combination of the graphics and multiprocessor algorithms allows the fast generation of many high-quality images.     

Software for drift compensation, particle tracking and particle analysis of high-speed atomic force microscopy image series

Atomic force microscopy (AFM) image acquisition is performed by raster-scanning a faint tip with respect to the sample by the use of a piezoelectric stage that is guided by a feedback system. This process implies that the resulting images feature particularities that distinguish them from images acquired by other techniques, such as the drift of the piezoelectric elements, the unequal image contrast along the fast- and the slow-scan axes, the physical contact between the tip of nondefinable geometry and the sample, and the feedback parameters. Recently, high-speed AFM (HS-AFM) has been introduced, which allows image acquisition about three orders of magnitude faster (500-100 ms frame rate) than conventional AFM (500 s to 100 s frame rate). HS-AFM produces image sequences, large data sets, which report biological sample dynamics. To analyze these movies, we have developed a software package that (i) adjusts individual scan lines and images to a common contrast and z-scale, (ii) filters specifically those scan lines where increased or insufficient force was applied, (iii) corrects for piezo-scanner drift, (iv) defines particle localization and angular orientation, and (v) performs particle tracking to analyze the lateral and rotation displacement of single molecules.     

Apport de la fusion d’images tomoscintigraphiques avec la tomodensitométrie X ou l’imagerie par résonance magnétique en pathologie osseuse : expérience du service de médecine nucléaire de Sfax

The aim of our study was to assess the contribution of image fusion of SPECT combined with computed tomography (SPECT-CT) or magnetic resonance imaging (SPECT-MRI) in our daily practice of bone scintigraphy. Seventeen patients underwent a SPECT image fusion, SPECT-CT or MRI in addition to conventional bone scintigraphy. These acquisitions are made separately with images stored in DICOM format. The fusion was operated after a manual coregistration of the images. Results show that in 35.29% of cases, the image fusion allowed to pinpoint the exact location of increased uptake seen on the whole body scan and/or on static images. In 35.29% of cases, the fusion has confirmed a diagnosis doubtful in planar imaging. In five patients, representing 29.41% of cases, the fusion has corrected a diagnosis. In one patient (5.88% of cases), the fusion has eliminated a false positive related to increased uptake visualized on the whole body scan. In two patients (11.11% of cases), the fusion has eliminated false negative of bone scan in one case and of MRI in the other case. Finally, in nine patients (50% of cases), the fusion has influenced the therapeutic management.     

A video image correlation technique for the measurement of electrophoretic mobility

The electrophoretic movement of blood cells has been examined with a video image correlator using the signal from a 625 line monochrome television camera attached to the optical arrangement. The diffraction pattern of a cell produces a characteristic signal which can be detected and registered in any television scan line to form the data of the first image frame. Under the influence of an electric field, cells moved across the television field of view and after a short interval appeared on different scan lines. The detection and registering process was repeated, and a cross-correlation function between the first and second image frame was computed. This function was stored in an output buffer which was continuously updated as fresh functions were integrated with the existing contents. The mean electrophoretic mobility of a suspension of particles can be calculated from the peak position of the integrated correlation function. Using a triangle deconvolution procedure, the relative contributions of subpopulations lymphocytes prepared from peripheral blood samples were examined.     

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.     

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 graphics with computerized tomography for functional neurosurgery

A computer graphics technique for computer-assisted stereotactic surgery is presented. The program is designed to aid the surgeon by presenting an on-line graphics display of stereotactic probes and electrodes superimposed on cross sections of the human brain stem. This technique simulates an otherwise blind surgical procedure on a graphics screen for use during surgery. An earlier system based around the DEC MINC-11 BA computer system has been used by the authors for the performance of stereotactic surgery with conventional ventriculography. This system has been upgraded and is now configured about an even more compact microprocessor-based hardware system with expanded graphics capabilities, which also allows its use with computerized tomography.