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Biomedical subjects

L D Harris

Publications and source records attributed to L D Harris.

At least 37 records · Page 2Linked to original sources
PubMed1981

Identification of the optimal orientation of oblique sections through multiple parallel CT images.

A method for identifying the optimal orientation of images of oblique sections computed from a "stack" of parallel computed tomography (CT) scans is presented. The identification of the optimal orientation is facilitated by the display of the stack of cross-sectional images (volume image) in three dimensions. Moreover, by displaying the section image as a brightened plane within the volume, imaged anatomic landmarks may be utilized to guide the process of identifying the desired image plane orientation. The volume image display method, termed projection imaging, involves the numerical projection of the volume picture elements (voxels) of the three-dimensional (3-D) reconstruction onto a plane to form a two-dimensional projection image. For X-ray CT, these projections are analagous to, and appear very much like, conventional radiographs. The volume image is seen in three dimensions by appropriately viewing stereo-pair projections of the volume formed from viewpoints that are 2 to 8 degrees apart. The display of the 3-D reconstruction as a volume image eliminates the need for the observer to mentally reconstruct the spatial relationships of the oblique section to anatomic features within the volume.

Animals↗
PubMed1980

Three-dimensional imaging of heart, lungs, and circulation.

A new imaging device, the dynamic spatial reconstructor (DSR), is described. It differs from commercially available computed tomography scanners in several ways. It images a volume rather than a slice; it images the volume in stop-action to minimize blurring due to motion; and it repeats the scan 60 times per second so that the functional movements of heart muscle and lung tissue and the distribution of roentgen contrast medium in blood can be quantitated in any portion of the body, especially in the heart, great vessels, and lungs. The system is under evaluation as a research tool for physiologic and, ultimately, clinical investigations.

Animals↗
PubMed1980

Physics and technical considerations in the design of the DSR: a high temporal resolution volume scanner.

A multiple x-ray source, high-speed, transaxial scanner system (DSR) is about to undergo evaluation studies. The capability for programmable scanning modes and operator-interactive retrospective reconfiguration of scan data makes the DSR a very powerful research tool. The physics and technological basis for system design and selection of several major components of the DSR scanner are discussed.

Humans↗
PubMed1980

Computed tomographic imaging of the heart: the dynamic spatial reconstructor.

A particularly important potential value of the Dynamic Spatial Reconstructor approach is that all the above data will be obtainable from a single injection of contrast agent into the right ventricle or pulmonary artery. On the basis of preliminary experimental data, a concentration of at least 80 mg of iodine per ml of contrast agent should be present in the aortic root for adequate opacification of the coronary arteries and myocardium; a bolus of at least 0.5 ml of contrast medium per kg, injected into the venous circulation, is required. As high-speed, volumetric imaging, computed tomographic scan machines such as the Dynamic Spatial Reconstructor become available with higher density resolution, perhaps a single injection of contrast agent into the right atrium or even a peripheral vein may be adequate to obtain all these measurements.

Animals↗
PubMed1979

Display and visualization of three-dimensional reconstructed anatomic morphology: experience with the thorax, heart, and coronary vasculature of dogs.

A new method, termed reprojection, is used to visualize anatomic morphology contained within three-dimensional reconstructions made up of images of multiple parallel cross sections. This method involves the projection, either orthographically into a plane or radially onto a cylinder, of the volume picture elements (voxels) of the reconstruction. Orthographic reprojection images, formed by mathematically summing the magnitudes of the voxels along selected parallel paths through the reconstructed volume, are analagous to conventional radiographs formed by the passage of an X-ray beam through the volume. The reprojection image is a two-dimensional array of picture elements that is displayed on a television monitor using a digital-to-video scan converter. Also described are the techniques of noninvasive selective tissue dissolution and numerical dissection, whereby obscuring portions of the reconstructed volume are either partially "dissolved" or totally eliminated before reprojection. Utilizing these methods, anatomic information present in a three-dimensional reconstruction but not clearly seen in a reprojection image is rendered visible after removal of superposed structures. The usefulness of these methods is demonstrated utilizing three-dimensional reconstructions of the thorax, heart, and coronary arteries of dogs.

Animals↗
PubMed1979

Distribution of regional volumes and ventilation in excised canine lobes.

A linear elasticity solution for the gravitational deformation of excised lungs was obtained. The accuracy of our solution was examined by comparing predicted and measured displacements of markers glued to the surface of canine lower lobes. The equations describing the strains in a lobe were used to predict the distribution of regional volumes and the slope of phase III (S3) of a single-breath oxygen (SBO2) test. The analysis predicted a negative S3. However, S3 was found to be positive in the five lobes tested, suggesting that factors other than gravity were responsible for the observed pattern of ventilation. In SBO2 tests repeated with increasing delays at end inflation, S3 progressively decreased, became negative, and was eventually abolished. Our equations predicted the most negative observed S3 well. We conclude that continuum mechanics can be used to describe the gravitational deformation of lungs and the resulting effect on ventilation distribution.

Animals↗
PubMed1978

Regional lung expansion at total lung capacity in intact vs. excised canine lungs.

A computer-based biplane videoroentgenographic recording technique that determines the spatial coordinates of radiopaque lung parenchymal markers was used to compare regional lung expansion at total lung capacity (TLC) in the intact dog (prone and supine) and after removal from the chest. The reproducibility of the technique was examined by repeated determinations of intermarker distances at various static lung volumes during stepwise inflation and deflation of the lungs. Most of the variability in repeated determinations of intermarker distances at any lung volume was due to cardiogenic motion. When marker positions were determined repeatedly at the same phase of the cardiac cycle, the maximum coefficient of variation was less than 3% for a marker pair separated by 16.5 mm. At TLC, distances between all intralobar marker pairs in the intact thorax (prone and supine) and excised were highly linearly related (r = 0.96-0.99), whereas distances between interlobar marker pairs did not correlate as well (r = 0.77-0.86). We conclude that at TLC 1) the intact thorax does not distort the shape of the individual lobes from the state of isotropic expansion, and 2) in different body positions, overall lung shape may be different due to displacementof lobes relative to each other, but individual lobes remain uniformly expanded.

Animals↗