Showing papers by "Michael W. Vannier published in 1985"

Multispectral analysis of magnetic resonance images.

Abstract: Magnetic resonance (MR) imaging systems produce spatial distribution estimates of proton density, relaxation time, and flow, in a two dimensional matrix form that is analogous to that of the image data obtained from multispectral imaging satellites. Advanced NASA satellite image processing offers sophisticated multispectral analysis of MR images. Spin echo and inversion recovery pulse sequence images were entered in a digital format compatible with satellite images and accurately registered pixel by pixel. Signatures of each tissue class were automatically determined using both supervised and unsupervised classification. Overall tissue classification was obtained in the form of a theme map. In MR images of the brain, for example, the classes included CSF, gray matter, white matter, subcutaneous fat, muscle, and bone. These methods provide an efficient means of identifying subtle relationships in a multi-image MR study.

Three-dimensional imaging of the wrist.

Abstract: The objective of this study was to determine the diagnostic quality of three-dimensional images of the carpal bones that could be constructed from raw data obtained from a computerized tomography scan. The quality of raw data collected was determined by collimation, slice interval, the number of projections, and x-ray tube operating specifications. The quality of two-dimensional images that were constructed from the raw data was determined by user-specified parameters including zoom or magnification factor, convolution kernels, and centering. The two-dimensional images were modified by erasure, the level of reconstruction, and animation, which permitted isolation of individual carpal bones, the construction of three-dimensional images viewing the external and internal surfaces of the bones, and the rotation of the images to provide multiple views. Representative images are presented.

Three-dimensional cranial surface reconstructions using high-resolution computed tomography.

Abstract: Until recently, there has been no satisfactory way for anthropologists to visualize intracranial morphology in more than two dimensions without actually “invading” the skull in some manner. Images provided by conventional x-ray and computed tomography (CT) scans are often abstract, flat, two-dimensional representations that fail to reveal three-dimensional relationships. We describe new computer-imaging techniques that reconstruct three-dimensional images from sequential series of narrowly collimated (1–2 mm), high-resolution CT scans of the skull. These computed images represent three-dimensional surface data and can be viewed from any direction. Depth information is encoded in gray scale. In addition, selected portions of the anatomy can be “removed,” i.e., made transparent, to allow visualization of previously hidden intracranial morphology. Since the geometric data obtained with the CT scanner are precise, parameters such as linear distances, angles, areas, and volumes can be accurately (and instantaneously) generated. The power and versatility of these computer-imaging techniques are demonstrated by examining (1) living subjects with major craniofacial dysmorphology (Treacher-Collins syndrome and unilateral coronal synostosis); (2) an anthropoid osteological specimen (Gorilla); and (3) a fossil mammal skull.

Generation of three dimensional images from CT scans: technological perspective.

Abstract: Routine production of three dimensional (3-D) surface images from CT scans for clinical applications has been performed in 700 cases. These images have been found useful in craniofacial, orthopedic, and neurosurgical applications. Three dimensional images may be produced on the same CT scanner that collected the original slices. The emergence of 3-D imaging as a routine radiological procedure involves special technological requirements to avoid artifacts and to produce a useful result. Three dimensional surface reconstruction procedures are reviewed and examples of clinical application are presented.

3-D Femoral Stress Analysis Using Ct Scans and P-Version Fem

Abstract: The potential of the finite element method as a computational aid for making objective clinical decisions has not yet been exploited due to the unreliability of the results obtained. The main reasons for this may be attributed to the poor quality of the finite elements available in the conventional softwares, improper modeling of the three dimensional problem, and errors introduced by incorrect representation of geometry and material properties. Herein, we report an attempt to derive a three-dimensional finite element model for the adult human femur which permits reliable representation of the local stress patterns. The geometry was obtained by serial computed tomography scans. The mechanical properties were based on laboratory tests and information available in the literature. The analysis is performed with a new generation software. Preliminary results suggest that the scheme could be automated and used for in vivo analysis.

Three-dimensional surface reconstruction for industrial computed tomography.

Abstract: Modern high resolution medical computed tomography (CT) scanners can produce geometrically accurate sectional images of many types of industrial objects. Computer software has been developed to convert serial CT scans into a 3-D surface form, suitable for display on the scanner itself. This software, originally developed for imaging the skull, has been adapted for application to industrial CT scanning, where serial CT scans through an object of interest may be reconstructed to demonstrate spatial relationships in three dimensions that cannot be easily understood using the original slices. The methods of 3-D reconstruction and solid modeling are reviewed, and reconstruction in three dimensions from CT scans through familiar objects is demonstrated.

Digital subtraction angiography of the coronary arteries.

Abstract: The application of digital coronary arteriography in the evaluation of patients with known or suspected coronary artery disease is considered. Digital imaging of coronary arteries and bypass grafts can augment 35-mm cineangiography and may eventually replace film for coronary arteriography. The clinical efficacy of both selective and nonselective digital coronary arteriography is not yet established, however, a number of advantages over 35 mm cine have now been delineated including high contrast sensitivity image subtraction and digital image processing. One particular advantage of digital coronary arteriography is the ability to perform an immediate quantitative analysis of coronary images providing a reliable and consistent measure of the significance of a stenotic lesion. Technical requirements for digital coronary arteriography include a high output X-ray generator, low noise television chain, a 512 X 512 digital image matrix, frame rates of at least 15 fps, and high data storage capacity of c500 megabytes. The utilization of digital coronary imaging as a supplement or in place of 35-mm cine angiography will provide improved coronary imaging and enable quantification for more accurate and clinically significant coronary artery imaging.