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Biomedical subjects

P Dev

Publications and source records attributed to P Dev.

26 records · Page 2Linked to original sources
PubMed1986

Perspective: three-dimensional imaging of the musculoskeletal system.

An evaluation of musculoskeletal disorders in 202 patients using three-dimensional CT displays has revealed the usefulness of the technique, especially in patients with fractures of skeletal areas with complex anatomy, articular disorders of the hip, and spinal stenosis. In some cases, plastic models of diseased areas have been created from the CT data and are reasonably accurate, providing a graphic representation of the disease and the ability to perform rehearsal surgery. A preliminary investigation of three-dimensional displays of MR images indicates that the technique is feasible, although its clinical practicality requires further analysis.

Fractures, Bone↗
PubMed1986

Three-dimensional imaging of bone from computerized tomography.

An automatic computer technique was designed to produce three-dimensional (3D) images of bony anatomy on a cathode ray tube (CRT) from computerized tomography (CT) data. The authors transferred CT scan data of a cadaver and 11 patients to a computer system via magnetic tape. An automatic edge extraction algorithm generated an outline of bone specified by a range of CT numbers for each scan slice. These outlines were stacked in the computer and various graphics options used to represent the 3D anatomy of bone on a high-resolution CRT screen. The 3D image data were interfaced with a three-axis computer numerically controlled milling device to produce solid models of these bone images. Comparison of the dimensions of the solid models of the femur, hemipelvis, and femoral medullary canal to the actual cadaver specimen demonstrated that the models were accurate in size to within 1-3 mm. These 3D images and solid models will be helpful for preoperative diagnosis, surgical planning, and customized prosthesis manufacture in complex orthopaedic cases.

Bone and Bones↗
PubMed1985

Three-dimensional imaging of the ankle joint from computerized tomography.

A computer system was developed to rapidly reconstruct three-dimensional (3D) images of bone from computerized tomography scans of the ankle joint. Solid models of the bones were produced from the 3D image data through the use of a computer numerically controlled milling machine. A cadaver ankle joint was scanned, and models of the distal tibia and fibula and dome of the talus were made and compared to the actual bone specimens. The measurements of the models were within 3 mm or less of the bones in all three planes (average, 1.2 mm or 5.5%). These 3D images and models of bone should allow better visualization of joint pathology and a system for preoperative planning on exact bone models to optimize the results of surgery.

Ankle Joint↗
PubMed1985

Three dimensional imaging of bone from analysis of computed tomography data.

A computer system was developed to reconstruct three dimensional images of bone from analysis of computed tomography data. Images of bone can be made within minutes and rotated for viewing from any direction. An editing process allows visualization of the articular surfaces of any joint. Solid models of the bone images can be produced with an accuracy of 1 mm to 3 mm by interfacing the image data with a computer numerically controlled milling machine. This technology will provide better information to the surgeon for preoperative diagnosis and planning and for the design of customized implants.

Adult↗
PubMed1984

Preliminary study of the upper limb with the use of ultrasound transmission imaging.

A biologically safe, noninvasive method for visualizing bone and soft tissue relationships has been developed recently. Termed the ultrasonic transmission imaging system, its advantages include visualization of soft tissues in real time while motion is underway. The image can be correlated to standard x-ray films, but since no ionizing radiation is involved, repeated risk-free visualization of extremities for either diagnostic assessment or biomechanical studies is permitted. Resolution of 1 mm and a depth of field of 8 mm are adequate for visualization of neurovascular bundles, tendons, ligaments, bones, and joints. The image can be digitized and stored for later analysis on computer graphic systems. Pilot studies have correlated the ultrasonic anatomy of normal and abnormal living and cadaver hands with known anatomic structures. The benefits to biomechanical analysis include the ability to visualize and accurately measure in a noninvasive manner the in vivo changes of position of tendons and other structures during movement. These initial efforts indicate the growing diagnostic and analytic capabilities of this instrument.

Evaluation Studies as Topic↗
PubMed1978

Effect of load disturbances during centrally initiated movements.

1. We have investigated the relative contributions of mechanical and reflex mechanisms in generating the forces produced by the neck muscles when loads were unexpectedly applied during centrally programmed head movements in monkeys. These movements, subserved by muscles well endowed with muscle spindles, are part of the coordinated eye-head response to the appearance of a stimulus in the animal's visual field. Our preparation was a chronically vestibulectomized monkey trained to make a visual discrimination. 2. Two procedures were used to evaluate the torque generated by the neck musculature when an unexpected load disturbance was applied: first, by surgically interrupting the afferent loop subserving the reflex action (section of cervical dorsal roots) and second, by building a mathematical model of the head-neck system and carrying out a process of simulation. 3. Our results indicated that the compensatory torque of reflex origin stimulated by the application of an opposing force was less than 10--30% of that required for perfect compensation, and the larger fraction of the observed compensation was due to the mechanical properties (inertial, viscous, and elastic) of the neck musculature. The combined action of reflex and mechanical processes never completely compensated for the disturbance.

Animals↗
PubMed1976

Electrotonic processing of information by brain cells.

In contrast to well-studied through-protection neurons that propagate information from one region to another in the central nervous system, short-axon or axonless neurons form local circuits, transmitting signals through synapses and electrical junctions between their dendrites. Interaction in this dendritic network proceeds without spike action potentials. Interaction is mediated by graded electrotonic changes of potential and is transmitted through high sensitivity (submillivolt threshold) synapses rather than by lower sensitivity (20 to 100-mv threshold) synapses typical of projection neurons. A crucial feature of local circuits is their high degree of interaction both through specialized junctional structures and through the extracellular fields generated by local and more distant brain regions. The anatomical evidence for the nature and distribution of neuronal local circuits in the nervous system is surveyed. Bioelectric mechanisms are discussed in relation to the special properties of local circuits, including dendrodendritic synapses, synaptic sensitivity, electrotonic coupling, and field effects. Intraneuronal and interneuronal transport of various types of substances suggests that the biochemical and the bioelectrical parameters are functionally interwoven. Through such interactions neuronal local circuits, with their distinctive properties, may play an essential role in higher brain function.

Action Potentials↗