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Biomedical subjects

R A Robb

Publications and source records attributed to R A Robb.

At least 73 records · Page 4Linked to original sources
PubMed1980

Evaluation of ischemic heart disease with a prototype volume imaging computed tomographic (CT) scanner: preliminary experiments.

A prototype synchronous volumetric computed tomographic X-ray scanner was used to demonstrate, in individual experiments, the possibility of estimating percent coronary arterial stenosis, regional myocardial blood supply and regional myocardial wall dynamics. Scans were obtained during angiography in intact anesthetized dogs or in an isolated metabolically supported working left ventricular preparation. Percent arterial stenosis was quantitated using the percent change in brightness area product of successive cross-sectional images of contrast agent-filled Tygon tubing sutured to the epicardium. Myocardial blood supply was evaluated by the transmural and circumferential extent and th time rate of change of myocardial opacification during coronary angiography. The regional time rate of change of left ventricular wall thickening during the systolic phase of the cardiac cycle was demonstrated in the isolated ventricle preparation. The recently installed Dynamic Spatial Reconstructor high speed volumetric scanning system will be used to make these measurements from scan data obtained during a single angiogram in man.

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

The dynamic spatial reconstructor: a computed tomography system for high-speed simultaneous scanning of multiple cross sections of the heart.

A new generation whole-body computed tomography system has been developed to provide accurate visualization and measurement of the vital functions of the heart, lungs, and circulation. This dynamic spatial reconstructor system (DSR) provides stop-action (.01-sec), rapidly sequential (60-per-second), synchronous volume (240 simultaneous adjacent 1-mm-thick transaxial sections) reconstructions and display of the full anatomic extents of the internal and external surfaces of the heart throughout successive cardiac cycles, and will permit visualization of the three-dimensional vascular anatomy and circulatory functions in all regions of the body of patients with cardiovascular and other circulatory disabilities.

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

The relationship of bone blood flow, bone tracer deposition, and endosteal new bone formation.

Bilateral defects of 4.5 by 11 mm were made in the distal one-third of the tibias of eight dogs and unilaterally in four dogs. Bone blood flow was measured by I-Ap washout, tracer deposition of 85Sr was determined, and extraction of 85Sr and [14C]sucrose was measured by the indicator-dilution technique. Endosteal new bone formation was determined by a combined tetracycline-microradiography method. There was a significant correlation between blood flow determined by washout (I-Ap determined over the area of healing bone) and endosteal new bone formation, p < 0.001, expressed as relationships (percent) of the area of new endosteal bone to the total area enclosed by the defect and the medullary cavity of the tibia, p < 0.001. This percentage ranged from 12% to 62% and was directly related to bone blood flow. This suggests that the increase in blood flow in new bone may be secondary to increased metabolic demands.

Animals↗
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

Reconstruction of a chromosome model from its projections.

As a pilot experiment towards the reconstruction of human chromosomes from their electron microscopic projections, a chromosome model was photographed and several cross-sectional planes successfully reconstructed. Some practical constraints and conditions for this type of work are defined.

Chromatin↗
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

High speed synchronous volume computed tomography of the heart.

A new generation, fully electronic high-speed whole-body computed tomography system is being developed to provide accurate dynamic visualization and measurement of the vital functions of the heart based on rapid changes in its shape, dimensions, and perfusion. This Dynamic Spatial Reconstruction System (DSR) will provide stop-action (1/100 sec.), rapidly sequential (60/sec.) synchronous volume (240 simultaneous, 1mm-thick cross sections) reconstructions and display of the full anatomic extent of the internal and external structures of the heart throughout successive cardiac cycles, and will permit visualization of the three-dimensional vascular anatomy and circulation throughout the myocardium.

Animals↗
PubMed1978

Quantitative measurement of fractional bone volume using digital scanning videodensitometry.

A method is described for reproducible and rapid quantitative measurements of fractional bone volume in sections of a bone biopsy. The presence or absence of bone is determined at several thousand points over the entire surface area of each specimen by high-speed digitization and computer analysis of video scans of enlarged microradiographic images of bone sections. An operator interactive light-pen assembly permits selective delineation of desired areas of the video image to facilitate computation of regional bone mass within each specimen. Tests of the reproducibility of the method of performed and are described. The results obtained from application of the method to determine the amount of bone in various age groups and in two groups of patients before and after therapy are also presented. These data indicate the potential of this technique for high volume, high resolution measurements of the fractional bone volume in both investigative and clinical diagnostic studies of age dependent and disease dependent processes.

Absorptiometry, Photon↗
PubMed1978

Quantitative imaging of the structure and function of the heart, lungs, and circulation.

A 28-x-ray-source, cylindrical-scanning, transaxial tomographic x-ray-imaging system is in the process of being fabricated. This system will scan synchronously up to 250 parallel transverse cross sections of the human body over an axial range of 25 cm within 0.01 second at a maximum rate of 60 scans per second. The system will provide numerous variations of scanning configurations to permit quantitative assessment of the relative importance of transverse section thickness, image contrast, spatial and temporal resolution, and related computerized algorithms and display techniques. Synchronous imaging at high temporal resolution of a three-dimensional volume--for example, the heart--eliminates the need for successive periods of breath-holding and gated imaging techniques and is essential for quantitation of cardiovascular and pulmonary function and structure in intact animals or humans. Initial clinical applications are expected to be in the early detection of lung cancer and the diagnosis of the nature and degree of congenital and acquired cardiovascular disabilities.

Animals↗
PubMed1977

Quantitation of left ventricular myocardial fiber hypertrophy and interstitial tissue in human hearts with chronically increased volume and pressure overload.

Using new techniques, we quantitated left ventricular myocardial fiber hypertrophy and interstitial tissue in four groups of autopsied hearts free of coronary disease: 1) 22 normal hearts, 2) 20 hearts from patients with mitral incompetence (NYHA Class II-III) who died early after mitral valve replacement from causes other than cardiac failure, 3) 22 hearts from patients with mitral incompetence (NYHA Class III-IV) who died early after mitral valve replacement from cardiac failure with low cardiac output syndrome, and 4) 22 hearts from patients with hypertensive heart disease (NYHA Class II-III). Myocardial fiber hypertrophy was quantitated by measuring cross-sectional myocardial fiber diameter; the proportion of interstitial tissue was quantitated by using a computerized, high-resolution video image-digitizing system. Myocardial fiber average diameter in groups 2, 3 and 4 was significantly higher than group 1. The proportion of interstitial tissue was significantly increased in group 3. In chronic mitral incompetence an increase in left ventricular interstitial tissue may play a role in the development of severe cardiac failure.

Cardiomegaly↗
PubMed1977

A computer-based videodensitometric system for studying banded human chromosomes illustrated by the analysis of the normal morphology of chromosome 18.

A computer-based, high-resolution, high-speed system is described for the digitization of television images of human G-banded chromosomes, on-line directly from a microscope. The digitized data are processed by a computer to determine the total length and centromere index of individual chromosomes and to obtain an integrated density profile representing the band pattern. The density profile is reduced by the computer to a series of dark and light bands, each with a defined position, width, and density. The results are displayed by the computer on a television monitor in a form that simulates routine laboratory preparations and that allows cytogenetic inspection. The system is easy to operate, and it includes a wide range of options for operator interaction to ensure reliability. The results of the computer analysis of the no. 18 chromosomes from five cells from each of 10 different persons demonstrated the usefulness of the system for detecting, measuring, and analyzing individual bands in human populations and its application to establishing band patterns of chromosomes in different states of contraction.

Azure Stains↗
PubMed1977

The effect of fixation with intramedullary rods and plates on fracture-site blood flow and bone remodeling in dogs.

Of fifty-seven adult dogs in which standard bilateral mid-ulnar fractures were produced, thirty-four had one side fixed with either a tight-fitting intramedullary Steinmann pin or a four-hole plate while the other side was not fixed, and twenty-three had a plate on one side and an intramedullary rod on the other. The blood flow at the fracture site, as determined by 85Sr clearance, was significantly less on the rod-fixed side than on the plate-fixed side at fourteen and ninety days, while the total ulnar blood flow was significantly higher on the rod-fixed than on the platefixed side at one and fourteen days but was the same on both sides thereafter. When the plate-fixed and rod-fixed fracture sites in the same dog were compared with respect to periosteal and endosteal bone formation as determined by tetracycline labeling anc microradiography, bone formation, like the blood flow, was greater in the callus of the ulnae fixed by plates. However, at ninety days, when healing had advanced to a point when the extent of union could be judged clinically, union had occurred in both ulnae of six of the seven dogs with both types of fixation studied at this time and was delayed in both ulnae of the remaining dog.

Animals↗