Plane-strain finite-element analysis of reconstructed diastolic left ventricular cross section.
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Animals↗
Biomedical subjects
R A Robb
Publications and source records attributed to R A Robb.
Biplane videoroentgenographic analysis of dynamic regional lung strains in dogs.
A method is described for determining the spatial distribution of pulmonary parenchymal strains in the intact canine thorax, using measurements of displacement of metallic (1-mm-diam)) markers percutaneously implanted throughout the parenchyma of the right lung. Dogs are supported head up or head down in a water-immersion respirator with the animal's airway connected to ambient air. Tracking of the parenchymal markers is accomplished by stereo biplane videoroentgenographic recordings, which allow high temporal (60/S) and spatial (+/- 1.5 mm) resolution measurements of the "tagged" lungs during various respiratory maneuvers. After transferring the video information to a stop-action video disc, an operator-interactive computer program is used to input the geometric coordinates of the markers into the computer. The true spatial coordinates are then determined after correction for pincushion and magnification distortions. Spatial and temporal distributions of regional parenchymal strains are obtained by determining the distance between markers on a frame-by-frame basis over the extent of the respiratory cycle. Data indicate nonuniformity in regional lung parenchymal strains.
Animals↗
Dynamic computer-generated displays of data from biplane roentgen angiography for study of the left ventricle.
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Angiocardiography↗
Three-dimensional visualization of the intact thorax and contents: a technique for cross-sectional reconstruction from multiplanar x-ray views.
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Analog-Digital Conversion↗
Dynamic three-dimensional reconstruction of beating heart and lungs from multiplanar roentgen-television images.
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Absorptiometry, Photon↗
The problem of accurate measurement of left ventricular shape and dimensions from multiplane roentgenographic data.
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Adult↗
A workstation for multi-dimensional display and analysis of biomedical images.
The capability to extract objective and quantitatively accurate information from 3-D radiographic biomedical images has not kept pace with the capabilities to produce the images themselves. This is rather an ironic paradox, since on the one hand the new 3-D and 4-D imaging capabilities promise significant potential for providing greater specificity and sensitivity (i.e. precise objective discrimination and accurate quantitative measurement of body tissue characteristics and function) in clinical diagnostic and basic investigative imaging procedures than ever possible before, but on the other hand, the momentous advances in computer and associated electronic imaging technology which have made these 3-D imaging capabilities possible have not been concomitantly developed for full exploitation of these capabilities. Therefore, we have developed a powerful new microcomputer-based system which permits detailed investigations and evaluation of 3-D and 4-D (dynamic 3-D) biomedical images. The system comprises a special workstation to which all the information in a large 3-D image data base 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 system, as well as some of the rationale, background, theoretical concepts, and practical considerations related to system implementation.
Computer Systems↗
Analyze: a comprehensive, operator-interactive software package for multidimensional medical image display and analysis.
A comprehensive software package, called ANALYZE, has been developed (1) which permits detailed investigation and evaluation of multidimensional biomedical images. ANALYZE can be used with 3-D imaging modalities based on x-ray computed tomography, radionuclide emission tomography, ultrasound tomography, and magnetic resonance imaging. The software is written entirely in "C" and runs on standard UNIX workstations. The ANALYZE package features integrated, complimentary tools for fully interactive display, manipulation and measurement of multidimensional image data. The software architecture permits systematic enhancements and upgrades which has fostered development of a readily expandable package. It provides an effective shell for custom software prototyping and turnkey applications. This paper provides a general description of this software as well as specific details on the methodology employed to develop it, both conceptual and technical. Applications of the software are illustrated.
Image Processing, Computer-Assisted↗
Virtual endoscopy: development and evaluation using the Visible Human datasets.
Virtual endoscopy (VE) is a new method of diagnosis using computer processing of 3D image datasets (such as CT or MRI scans) to provide simulated visualizations of patient specific organs similar or equivalent to those produced by standard endoscopic procedures. Conventional endoscopy is invasive and often uncomfortable for patients. It sometimes has serious side effects such as perforation, infection and hemorrhage. VE visualization avoids these risks and can minimize difficulties and decrease morbidity when used before actual endoscopic procedures. In addition, there are many body regions not compatible with real endoscopy that can be explored with VE. Eventually, VE may replace many forms of real endoscopy. There remains a critical need to refine and validate VE visualizations for routine clinical use. We have used the Visible Human Dataset from the National Library of Medicine to develop and test these procedures and to evaluate their use in a variety of clinical applications. We have developed specific clinical protocols to compare virtual endoscopy with real endoscopy. We have developed informative and dynamic on-screen navigation guides to help the surgeon or physician interactively determine body orientation and precise anatomical localization while performing the VE procedures. Additionally, the adjunctive value of full 3D imaging (e.g. looking "outside" of the normal field of view) during the VE exam is being evaluated. Quantitative analyses of local geometric and densitometric properties obtained from the virtual procedures ("virtual biopsy") are being developed and compared with other direct measures. Preliminary results suggest that these virtual procedures can provide accurate, reproducible and clinically useful visualizations and measurements. These studies will help drive improvements in and lend credibility to VE procedures and simulations as routine clinical tools. VE holds significant promise for optimizing endoscopic diagnostic procedures, minimizing patient risk and morbidity, and reducing health care costs.
Anatomy, Cross-Sectional↗
Parametric display of myocardial function.
Quantitative assessment of regional heart motion has significant potential to provide more specific diagnosis of cardiac disease and cardiac malfunction than currently possible. Local heart motion may be captured from various medical imaging scanners. In this study, 3-D reconstructions of pre-infarct and post-infarct hearts were obtained from the Dynamic Spatial Reconstructor (DSR)[Ritman EL, Robb RA, Harris LD. Imaging physiological functions: experience with DSR. Philadelphia: Praeger, 1985; Robb RA, Lent AH, Gilbert BK, Chu A. The dynamic spatial reconstructor: a computed tomography system for high-speed simultaneous scanning of multiple cross sections of the heart. J Med Syst 1980;4(2):253-88; Jorgensen SM, Whitlock SV, Thomas PJ, Roessler RW, Ritman EL. The dynamic spatial reconstructor: a high speed, stop action, 3-D, digital radiographic imager of moving internal organs and blood. Proceedings of SPIE, Ultrahigh- and High-speed Photography, Videography, Photonics, and Velocimetry 1990;1346:180-91.] (DSR). Using functional parametric mapping of disturbances in regional contractility and relaxation, regional myocardial motion during a cardiac cycle is color mapped onto a deformable heart model to facilitate appreciation of the structure-to-function relationships in the myocardium, such as occurs in regional patterns of akinesis or dyskinesis associated with myocardial ischemia or infarction resulting from coronary artery occlusion.
Animals↗
Validation of three-dimensional reconstructions of knee anatomy: CT vs MR imaging.
This is the first investigation to validate the accuracy of spatial measurements based on computer-generated three-dimensional (3D) reconstructions of CT and magnetic resonance (MR) scans. Standard 3D reconstructions of one fresh frozen cadaveric knee specimen with implanted stereotactic reference markers were created. These reconstructions were based on the data from CT and MR scans performed before and after the resection of extraosseous soft tissues. The distances between the stereotactic reference markers in the 3D reconstructions were compared with the same measurements of the specimen using a Bridgeport milling machine as a precision 3D digitizer. The accuracy of intermarker distance measurements averaged 99% for CT-based reconstructions compared with 97.5% for MR-based reconstructions. Planar slices at a predetermined level and orientation through the femoral condyles were created by sequential milling of the specimen and were compared with reconstructed oblique planar CT and MR slices at the same level and orientation. The accuracy of condylar dimensional measurements was 94% for CT and 93% for MR compared with measurements of the milled slices. Three-dimensional reconstructions based on CT and MR scan data were of equally high quality and were unaffected by the status of the soft tissues.
Computer Simulation↗
Analysis of periprosthetic tissue formation around a porous titanium endoprosthesis using CT-based spatial reconstruction.
OBJECTIVE: Reformatted CT-based image data may be of use in evaluation of new bone formation around massive bone replacement implants, but the impact of metal-induced artifacts on the accuracy of image reconstruction is unknown. This study was designed to evaluate the accuracy and precision of quantitative image reconstruction in the presence of a titanium implant. MATERIALS AND METHODS: Model porous-coated titanium implants were harvested from 23 dogs 12 weeks after surgical implantation. Contiguous 1.5 mm transverse CT scans were done first with the titanium implant in place, then repeated after replacement of the implant with an acrylic spacer. Microradiographs of sections cut at defined locations were used to establish gray level thresholds for image reconstruction and to validate the accuracy of CT-based image data. Reformatted image data were used to determine periprosthetic bone volume (mm3) and area of interfacial contact between bone and implant (mm2). RESULTS: The CT-based data derived with either implant material had an accuracy of 83-88% and a precision coefficient of variation (CV) of 2-4% for both volume and contact area variables. Presence of titanium did not seriously affect the quality of images obtained, and results were strongly correlated with those obtained with acrylic. CONCLUSION: Accurate volumetric data derived from CT-based images of periprosthetic new bone formation can be obtained in the presence of a titanium endoprosthesis. Improved demonstration of spatial relationships of bone and implant may improve postoperative evaluation.
Animals↗
Mayo Clinic and Medical School Biodynamics Research Unit.
The facilities that make up the Mayo Biodynamics Research Unit include the dynamic spatial reconstructor (DSR), which when fully operational will generate raw data at 200 million samples per second. Processing of these data will require a computer capable of several billion arithmetic operations per second.
Biomechanical Phenomena↗
Noninvasive numerical vivisection of anatomic structure and function of the intact circulatory system using high temporal resolution cylindrical scanning computerized tomography.
A high temporal resolution cylindrical scanning computerized tomographic system (DSR) is being built for study of anatomic structural/functional relationships of heart, lungs, vascular anatomy, and circulatory dynamics in any region of the body. Unlike current commercial CT scanners which scan only one or, at most, a few cross sections at a time, cylindrical scanners such as the current Mayo SSDSR and upcoming DSR scan nearly 250 cross sections simultaneously. Twenty-eight or more multiplanar images over a range of 160 or more degrees of an entire rapidly moving structure such as the heart or a segment of the circulation will be recorded in periods as short as 10 msec by the DSR at 60/sec rates and stored in computer memory. The scanned volumes can then be sectioned mathematically in any direction at will, including zooming in on regions of interest to problems at hand (e.g., clinical diagnoses). Progression from biomedical investigation to practical clinical and health care uses requires development of special-purpose, readily replicable, economical (but very high speed and volume) data handling and computational devices. The ultimates overall objective is to quantitatively characterize the performance of the human cardiopulmonary and circulatory systems utilizing pertubations associated with various types of physiologic stress and congenital or acquired disease processes including neoplasia.
Animals↗