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Biomedical subjects

T M Peters

Publications and source records attributed to T M Peters.

At least 55 records · Page 3Linked to original sources
PubMed1983

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.

Brain Diseases↗
PubMed1981

Clinical application of multiplanar computerized tomography of the orbit.

Multiplanar image reconstruction involves the reconstruction of sagittal, coronal or oblique views form a series of transverse computerized tomography images without exposing the patient to more radiation. The technique, especially when used in conjunction with high-resolution scanning, is invaluable in the diagnosis of lesions within the orbit. This paper deals with the clinical application of this new technique.

Humans↗
PubMed1980

Multi-planar transformation of CT images.

A software package has been developed to permit sagittal or coronal sections to be computed and displayed interactively on an EMI CT scanner or independent viewing unit. The efficiency of the system is achieved by using a novel data transformation to store compressed data on the computer disc. Several examples illustrate the use of this system and show the benefit of utilizing post-processing operations such as filtering and image averaging on the reconstructed vertical slices.

Data Display↗
PubMed1977

Computed tomography with fan beam geometry.

Data collection for computed tomography (CT), using a fan beam of radiation, is considered in detail. The manner in which the required projection data set is built up as scanning proceeds is demonstrated. It is shown that by offsetting the fan beam detector from its symmetrical position by a fraction of the element spacing, and by making measurements over 360 degrees, the spatial resolution of the detector may be increased by up to a factor of two. Results of simulations relating to an actual CT device under construction are presented.

Mathematics↗
PubMed1976

Diagnosis of gross vesico-ureteric reflux using ultrasonography.

A simple non-invasive ultrasonic technique which identifies gross vesico-ureteric reflux (VUR) in adults is described. It is based on the time position (TP)-mode (or M-mode) of ultrasound imaging. This method warrants assessment as a possible screening procedure for gross VUR in newborn children.

Dilatation, Pathologic↗
PubMedDate not supplied

Integration of stereoscopic DSA and 3D MRI for image-guided neurosurgery.

We demonstrate the feasibility and utility of using anatomical/vascular correlation in image-guided surgery, by interfacing a PC-based stereoscopic Digital Subtraction Angiography (DSA) analysis system to a three-dimensional (3D) image based surgical workstation that has been modified to allow presentation of stereoscopic images. Numerical values representing the position and angulation of a hand-held probe are transmitted to both systems simultaneously, enabling the probe to be visualized stereoscopically in both anatomical and vascular images during the surgical procedure. The integration of the patient's vascular and anatomical data in this way provides the surgeon with a complete overview of brain structures through which he is passing the electrode-guiding cannulas, enabling him to avoid critical vessels en route to the targets.

Algorithms↗
PubMedDate not supplied

Dose distributions in dynamic stereotactic radiosurgery.

A treatment planning technique for calculation of dose distributions in dynamic stereotactic "radiosurgery" with a 10-MV isocentrically mounted linear accelerator is presented. The treatment planning for dynamic radiosurgery is a three-dimensional problem, since during treatment both the gantry and the couch rotate simultaneously, the gantry from 30 degrees to 330 degrees and the couch from 75 degrees to - 75 degrees. The patient surface and anatomical information is obtained from a family of computed tomography or magnetic resonance scans, and a stereotactic frame is used for target localization, treatment setup, and patient immobilization during the treatment. The dose calculational algorithm follows the gantry and couch rotation in an incremental fashion, and relies on measured stationary beam central axis percentage depth doses and dose profiles to calculate the normalized tissue-maximum-ratio distributions over a matrix of points defined on one of three orthogonal planes (transverse, sagittal, or coronal). The dose calculation algorithm is discussed in detail and calculated dose distributions for single plane and dynamic radiosurgery compared with measured data.

Brain Diseases↗
PubMedDate not supplied

Dose distributions in radiosurgery.

A PC-based, three-dimensional treatment planning system, which may be used for planning of radiosurgical treatments with the Gamma unit or with any of the radiosurgical techniques based on isocentric linear accelerators (linacs), is described and used to calculate isodose distributions for various linac-based radiosurgical techniques ranging from the single plane rotation to a 4-pi geometry. The latter gives an isotropic dose falloff outside the target volume but cannot be used for practical radiosurgery, while the single plane rotation is simple to use but gives unacceptably shallow dose falloffs in the transverse plane. Dose falloffs for several other techniques of varying degrees of complexity are shown and discussed. Also discussed is the effect of beam energy and beam profiles on radiosurgical dose distributions.

Humans↗
PubMedDate not supplied

Multimodality image integration for stereotactic surgical planning.

A method is presented for integrating stereotactic projection and tomographic image data to give composite 3-D images (stereo pairs) of cerebral anatomy and vasculature. The technique serves to combine complementary information from each modality and allows the imaged volume to be viewed directly. The procedure is largely automated and requires no additional apparatus or information beyond that which is ordinarily employed during stereotactic surgical planning. The two types of data are combined by superimposing the projection angiogram (DSA) onto a translucent volume rendered CT or MR image. Since the rendering algorithm employs an orthographic projection technique, the tomographic volume must first be reshaped and oriented to yield a perspective view that matches the DSA projection. During this process, the data undergo various interpolations which consequently affect the accuracy of target identification based on the resulting images. The integrity of the matching procedure was assessed using simulated data sets. Also, calculations were performed to estimate the resolution of measurements made from digitized stereoscopic images. The resulting sub-pixel accuracy of the matched images suggests that the technique has potential for stereotactic applications. Preliminary results are presented illustrating combined CT-DSA and MR-DSA data sets.

Angiography, Digital Subtraction↗
PubMedDate not supplied

Analysis of projection geometry for few-view reconstruction of sparse objects.

In this paper certain projections are examined as to why they are better than others when used to reconstruct sparse objects from a small number of projections. At the heart of this discussion is the notion of "consistency," which is defined as the agreement between the object's 3-D structure and its appearance in each image. It is hypothesized that after two or more projections have been obtained, it is possible to predict how well as subsequent view will perform in terms of resolving ambiguities in the object reconstructed from only the first few views. The prediction is based on a step where views of the partial reconstruction are simulated and the use of consistency to estimate the effectiveness of a given projection is exploited. Here some freedom is presumed to acquire arbitrary as opposed to predetermined views of the object. The principles underlying this approach are outlined, and experiments are performed to illustrate its use in reconstructing a realistic 3-D model. Reflecting an interest in reconstructing cerebral vasculature from angiographic projections, the experiments employ simulations based on a 3-D wireframe model derived from an internal carotid arteriogram. It is found that for such an object, the predictions can be improved significantly by introducing a correction to account for the degree to which the object possesses some symmetry in shape. For objects sufficiently sparse, this correction is less important. It is concluded that when the number of projections is limited, it may be possible to favorably affect the reconstruction process in this manner.

Angiography, Digital Subtraction↗