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Biomedical subjects

R A Robb

Publications and source records attributed to R A Robb.

At least 55 records · Page 3Linked to original sources
PubMed1990

Three-dimensional reconstruction of the temporal bone.

Study of the complex anatomy and pathology of the temporal bone has traditionally used microscopy which permits analysis in only two dimensions. Recent advances in bioimaging technology have permitted visualization and reconstruction of computed tomography images in three dimensions. We have developed a technique that applies this technology in the imaging and reconstruction of human temporal bones. Data taken from serial histologic sections of the temporal bone are entered into a computer. The sections are edited and, through the use of specially developed software, a realistic three-dimensional reconstruction is produced. The reconstructed image can be rotated along any of three axes, and structures within the temporal bone can be isolated for more detailed analysis. Applications for the study of pathologic conditions of the temporal bone will be discussed.

Adult↗
PubMed1987

A system for interactive volume analysis (SIVA) of 4-D biomedical images.

We have developed a powerful new microcomputer-based system that permits detailed investigations and evaluation of 3-D and 4-D (dynamic 3-D) biomedical images. The system comprises a special work station to which all the information in a large 3-D image database is accessible for rapid display, manipulation, and measurement. The system provides important capabilities for simultaneously representing and analyzing both structural and functional data and their relationships in various organs of the body. This paper provides a detailed description of this sophisticated system, as well as the rationale, background, theoretical concepts, and practical considerations related to implementation of even more advanced capabilities for interactive display and analysis of 4-D biomedical images.

Computers↗
PubMed1985

Three-dimensional cardiac anatomy and function in heart disease in adults: initial results with the dynamic spatial reconstructor.

The dynamic spatial reconstructor, or DSR, is a unique high-speed volume-imaging x-ray scanner based on computed tomographic principles. In this report, we present data obtained from the first feasibility DSR studies of adult patients with heart disease. Information from three patients--one with hypertrophic obstructive cardiomyopathy, one with calcific aortic valvular disease, and one with a left ventricular aneurysm--is described in detail. The mean DSR scanning time for each patient was 20 seconds, and the mean total irradiation to the sternum was 15.3 R. Transverse cross sections were reconstructed and then retrospectively reformatted to provide operator-selected oblique sections in space (for example, long-axis and short-axis sections of the left ventricle), to follow these sections through time (such as from end-diastole through end-systole), and to create three-dimensional displays (for instance, of the left ventricular chamber). Unique quantitative measurements of structure and function were made by using these images. For generation of most imaging data, only one injection of contrast material into the right side of the heart is necessary. Clinically useful three-dimensional dynamic imaging data can be acquired from adult patients with heart disease by using the DSR. Compared with conventional angiocardiography, DSR studies can provide information with less x-ray exposure and fewer angiographic injections.

Adult↗
PubMed1984

The Dynamic Spatial Reconstructor: investigating congenital heart disease in four dimensions.

The Dynamic Spatial Reconstructor (DSR) is a high-temporal resolution, three-dimensional (3-D) X-ray scanning device based on computed tomography (CT) principles. It was designed for investigation of some problems inherent in current diagnostic imaging techniques, and to allow quantitative studies of cardiovascular structure and function. One of the research protocols in which DSR is currently used involves studying selected pediatric patients with complex congenital heart disease. Initial results show that 3-D dynamic images can be obtained from these patients with minimal invasiveness and that these images may provide useful diagnostic information.

Adolescent↗
PubMed1984

Quantitative analysis of a vascular tree model with the dynamic spatial reconstructor.

The accuracy in determining the three-dimensional anatomy of a vessel network by computed tomography (CT) is evaluated using a glass model of a pulmonary artery. The dynamic spatial reconstructor (DSR), a high temporal resolution, volumetric, roentgenographic, CT scanner, was used to scan the model. The glass of the model had a roentgen attenuation coefficient mu = 0.55 cm-1, which is approximately equivalent to the 20% dilution of contrast medium to be expected in the pulmonary arterial tree following a contrast agent bolus injection of 2 ml/kg in the right atrium. The model was scanned inside a 20 cm diameter Plexiglas cylinder with a 1 cm thick wall (mu congruent to 0.2 cm-1) to simulate the chest wall of a 20 kg dog, and it was filled with potato flakes to simulate lung parenchyma (mu congruent to 0.06 cm-1). In one 0.011 s scan, information for reconstruction of a stack of images of transaxial sections was recorded. Sequential scans were performed to obtain data for either maximum transaxial resolution (14 angles of view every 0.0167 s, 120 parallel slices each 1.8 mm thick) or maximum axial resolution (eight angles of view every 0.0167 s, 240 parallel slices each 0.9 mm thick) reconstructions. Estimated detectable "vessel" size, cross-sectional area, branching angle, and interbranch segment length were determined as a function of imaged slice thickness, orientation of section image, and number of angles of view (i.e., scan duration) used to make images. Retrospective selection of 0.05 s duration scan apertures at sequential 0.5 s intervals was used to simulate a typical, retrospectively gated reconstruction from a DSR scan. Using these reconstructed images, 2 mm diameter "vessels" could be readily detected and their structure quantitated. Comparing direct measurements and DSR estimates, cross-sectional area (SEE = 3 mm2), branching angles (SEE = 2 degrees), and segment length (SEE = 1 mm) all had a correlation coefficient greater than 0.99, and the regression lines showed no significant differences from the lines of identity (p greater than 0.05).

Animals↗
PubMed1984

Mass of left ventricular myocardium estimated with dynamic spatial reconstructor.

Using the Dynamic Spatial Reconstructor (DSR), a unique multiple X-ray source, high-repetition-rate CAT scanner, we estimated left ventricular (LV) myocardial volume and chamber volume of eight dogs ranging from 2.5 to 32.5 kg. Dogs were given subcutaneous morphine (3 mg/kg) and anesthetized with intravenous pentobarbital sodium (22 mg/kg). A bolus of 1 ml/kg body wt contrast medium was injected into the superior vena cava and 60/s scans repeated over 7 s were performed. Each 0.0167-s scan generated image data for 120 1.8-mm-thick transverse slices, in the dextro and levo phases of the angiograms. Retrospective reformatting of the scan data was used to generate images of thin slices perpendicular to the aortoapical axis of the LV. The LV muscle and chamber volumes were estimated from their outlines in each imaged slice using a manually operated trackball interfaced to a computer. Values of the LV muscle ranged from 18.0 to 146.8 cm3 by DSR and showed a good correlation with the postmortem values (r = 0.99, y = 0.94x + 4.1). Ratios of volume of the myocardium to chamber volume ranged from 1.19 to 3.10.

Animals↗
PubMed1983

Noninvasive quantitative imaging of shape and volume of lungs.

The Dynamic Spatial Reconstructor (DSR) can be used to determine detailed structure-to-function relationships or organ systems in vivo. A basic index of lung structure (shape and dimensions) is total lung volume. We checked the accuracy with which in vivo lung volumes can be measured by comparing lung volume (air plus tissue) determined by DSR scanning with that determined by excision and water displacement. Six dogs (2.5-26 kg) under morphine-pentobarbital anesthesia were scanned supine or prone at functional residual capacity and/or total lung capacity. With the trachea clamped at the lung volume scanned, a lethal dose of pentobarbital was administered, the lung excised, and its volume determined by water displacement. In vivo scan data were used to reconstruct adjacent 0.9-mm-thick transverse sections over the entire axial extent of the thorax. A three-dimensional surface-detection algorithm was used to generate shaded surface displays of the in situ lungs. The number of voxels (volume picture elements) of known dimensions contained within the three-dimensional image of the lung was summed to estimate total lung volume. Lung volumes calculated from the in vivo images ranged from -3.4 to +2.3% of the lung volume determined in vitro. The mean difference was 1.38 +/- 0.07% (SE). Regression analysis yielded an r value (correlation) of 1.00, a slope of 0.99, and an intercept of -4.35 ml. Multiple lung inflation steps scanned and analyzed in one dog showed similar accuracy. This technique is applicable to subjects with thorax dimensions up to 42 cm in cephalocaudal height and 39 cm in ventrodorsal and transverse diameters.

Animals↗
PubMed1983

Pharmacy department costs and patient charges associated with a home parenteral nutrition program.

The pharmacy department costs of a home parenteral nutrition (HPN) program were identified, and the patient charges for HPN were compared with the charges for hospitalization for parenteral nutrition. Ten patients were randomly selected from 55 patients active in the HPN program at the University of Washington Hospital. Cost identification included quantification of supplies, personnel, equipment, freight, miscellaneous, and indirect costs. Patient charges were identified through billing documents. Charges included clinic visits and laboratory tests. Inpatient charges were identified in a similar manner and included a standard daily hospital charge. Average yearly costs to the pharmacy department were nearly +9000 per HPN patient. Patient charges for HPN were +48.19 per infusion day compared with +205.68 per infusion day for the hospitalized patient. The cost savings of HPN to the patient and the hospital were clearly demonstrated.

Costs and Cost Analysis↗
PubMed1983

Subjective assessment of patient outcomes of home parenteral nutrition.

The medical, financial and psychosocial impact of home parenteral nutrition (HPN) therapy on patients' lives was assessed. A questionnaire that solicited patient characteristics and therapeutic outcomes of HPN therapy, such as number of hospital admissions, physiological complaints, and psychosocial interferences, was sent to 49 patients currently participating in a HPN program based at a university hospital. Questionnaires were returned by 42 patients. HPN-related complications were responsible for 39% of all reported hospital admissions during the previous year; of these, 27% were related to HPN catheters. Patients reported few physiological complaints, except for cramping in the hands and feet. Patients who complained of diarrhea had significantly more physiological complaints and psychosocial interferences than those who did not. The majority of patients had medical insurance coverage, but 26% had to pay at least part of the costs of HPN therapy. Only 25% of patients who were able to work did so. Most patients believed that HPN therapy had a very positive effect on their lives. The majority of patients in this HPN program appear to have a reasonable quality of life.

Adult↗
PubMed1982

Dynamic volume imaging of moving organs.

The Dynamic Spatial Reconstructor system has been developed to dynamically (up to 60/sec) image the entire 3-D volume (up to 240 adjacent 1-mm-thick transverse sections) encompassing moving organs of the body, particularly the heart and lungs, or the circulation in any organ. This capability permits accurate regional and global measurements to be made of the important relationships between structure and function within and among these organs, which in turn facilitates achievement of new insights into the basic physiological processes of these organs, and promises increased sensitivity and specificity in the diagnosis of pathology that affects normal organ function. This article explains the biomedical and technological rationale for development of the DSR, describes the design concepts and practical operation of the system, and presents preliminary results obtained with the system, including initial data from one of the first patient studies.

Animals↗
PubMed1982

Three-dimensional spatial, density, and temporal resolution of the dynamic spatial reconstructor.

Spatial, density, and temporal resolution of the dynamic spatial reconstructor (DSR), a multiple X-ray source, high speed, computed tomography scanning system, are evaluated. Hole-pair resolution was evaluated in a stationary phantom surrounded with air, 15 cm of water, or 20 cm of water. Temporal resolution was evaluated by rotation of one of the resolution phantoms during the scan, and with a balloon inflated to a known volume and at a known rate to approximate a typical left ventricular chamber volume and filling rate. These studies confirmed that the spatial resolution is essentially the same in the transverse and axial directions, and that retrospective manipulation of the image data is important for maximization of spatial and density resolution in any structure under examination by obtaining a tradeoff with partial-volume and motion-blurring effects. Maximum spatial resolution in the scanned volume was shown, under ideal conditions, to be greater than five hole pairs per centimeter. Under conditions of intravenous injection of contrast agent, the resolution of blood vessels in an experimental animal approximately 25 kg in weight is expected to be on the order of three hole pairs per centimeter; and in an adult human weighting approximately 60 kg, a resolution of about two hole pairs per centimeter is to be expected.

Angiography↗
PubMed1982

X-ray computed tomography: an engineering synthesis of multiscientific principles.

The discovery of X-rays in 1895 heralded a new era in the practice of medicine-visualization into the body without painful and often life-threatening surgery. The discovery was almost immediately recognized and accepted for its potential as a new medical diagnostic technique, a methodology which has been characterized by many evolutional improvements during the intervening 85 years. These advances have been perpetuated by development of more sophisticated and powerful instruments which have broadened and refined the utilization of X-rays for medical imaging. However, not until the early 1970s did any new implementation of X-ray imaging have revolutionary impact on the practice of medicine. In 1971 an X-ray scanner was developed which produced cross-sectional images of the brain by employing several different scientific concepts, some known for over 50 years. The reduction of these concepts to practice was a significant scientific achievement, and was based on a precisely engineered instrument which transmitted X-rays through the body and recorded their attenuation around 180 degrees, providing the data for computation and display of cross-sectional images of the body. Although the decade of the 1970s has seen this new technology-called X-ray computed tomography (CT)-develop and expand into several areas of application, the foremost of these remains in medical imaging whereas phenomenal evolution in capabilities of CT scanners has occured. However, the trend toward faster scanners with concomitant improvements in imaging accuracy holds promise for significant applications in basic biomedical and physiological research as well, with capabilities for quantitative analysis of anatomic-physiologic relationships and for noninvasive diagnostic body tissue examination and determination of tissue characteristics which have heretofore been possible only by surgical procedures, histological techniques, and/or pathological dissection at autopsy. This review chronicles the relatively short history of X-ray computed tomography and attempts to put in perspective the fundamental reason for its remarkable success, namely that it derives from an ingenious engineering synthesis of several well-founded principles in the basic and applied sciences.

Humans↗
PubMed1982

Integrated calculator programs for pharmacokinetic calculations.

A package of integrated programs for calculating pharmacokinetic variables and drug-dosing regimens using a hand-held programmable calculator is described. Twelve pharmacokinetic programs, which were based on previously published pharmacokinetic equations, were developed for use in a HP-41C hand-held calculator (Hewlett-Packard). The programs perform, pharmacokinetic calculations for many drugs, including digoxin, theophylline, phenytoin, nd the aminoglycosides. Also programs for ideal body weight, body surface area, and creatinine clearance calculations are included. Eleven of the 12 programs can be stored in the calculator at any time. Values generated in one program are stored in memory registers and can be recalled directly for use in other programs. The calculator has a continuous memory; therefore, all stored data, programs, and functions are maintained when the calculator is turned off. The integrated calculator programs provide a quick and reliable means of applying pharmacokinetic principles to everyday hospital pharmacy practice.

Computers↗