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Biomedical subjects

R S Ledley

Publications and source records attributed to R S Ledley.

16 recordsLinked to original sources
PubMed1979

Application of the ACTA-scanner to visualization of the spine.

The development of a new computer program called VISUAL, designed to be applied to a series of cross-sectional ACTA scans of the body, makes possible the three-dimensional visulaization of spinal structure without the necessity of surgical exploration. With VISUAL, a molded three-dimensional image of the spine can be displayed on a CT scanner monitor from any of several angles, or from several angles successively, with the direction of illumination determined by the operator.

Computers↗
PubMed1978

Medical technology and cost containment: two applications of operations research.

The government proposes "common sense" regulations to help contain rising health costs due to the increasing use of high-technology procedures, such as computerized tomography scanning. Two illustrations are given showing that such ad hoc regulations may have the effect of increasing costs and are certainly far from the optimum obtained by known methods of operations research.

Computers↗
PubMed1978

Evaluation of calcium concentration in bones from CT scans.

Fresh cadaveric lumbar vertebrae from 28 subjects were obtained at autopsies and then analyzed by CT scans. An average CT number, calibrated against water and representing the relative x-ray attenuation coefficient of cancellous bone of each vertebra, was obtained. Calcium concentrations in milligrams per cubic centimeter for each vertebral specimen, calculated by physical methods, were plotted against the average CT numbers. The results suggest a linear relationship between the CT numbers and the calcium content of bone.

Adult↗
PubMed1977

Radiotherapy treatment planning using the ACTA-scanner.

Computerized tomography is useful in radiotherapy treatment planning in the following ways: (1) Its image provides the most accurate possible contour of the patient and demonstrates the internal structures in their proper relation to each other. (2) The tumor and its extension are accurately demonstrated. (3) Corrections for tissue heterogeneities can be accomplished in one of two ways, either by arbitrary assignment of densities to tissues or by direct scanning with a therapy source. This latter procedure is under investigation. (4) The computer can be programmed to demonstrate summations of dose delivered from multiple fields.

Dose-Response Relationship, Radiation↗
PubMed1977

A forthcoming cross-sectional atlas correlating CT scans with anatomical structures.

With the development of the whole-body CAT (computerized axial tomographic) scanner, a need has arisen for a cross-sectional anatomy book that correlates acutal CT scans with detailed anatomical structures. This article describes a forthcoming cross-sectional atlas using CT scans of normal living human volunteers. After a preliminary discussion of such considerations as some fundamental differences between cross-sectional anatomy and conventional anatomy and the relationship between cross-sectional anatomy and computerized tomography, there is an explanation of the textual format. This section includes a description of the presentations on the pages, the use of color in the scans, and the use of certain advanced features of the ACTA-Scanner, the scanner used for the atlas. The final part of the article illustrates sample scans and a diagram from the forthcoming test.

Anatomy↗
PubMed1975

Computerized axial tomography in syringomyelia.

The ACTA-scanner, a device for computerized axial tomography, permits cross-sectional radiographic study of the entire human body, including the spine. In the ACTA-scan, the spinal cord appears as a roundish formation surrounded by the less dense subarachnoidal cerebrospinal fluid. The spines of 18 patients with verified (nine cases) or suspected (nine cases) syringomyelia were studied by ACTA-scanning. In seven of the verified and in four of the nonverified cases, some evidence of cord cavitation was shown. The cystic part of a cervical-cord ependymoma was also demonstrated. ACTA-scanning is an easily performed, noninvasive, innocuous procedure. This technic, which complements other radiographic methods of evaluating the spinal cord, is particularly suitable for screening and follow-up study of patients with syringomyelia. The easily accomplished recognition of a possible associated hydrocephalus is an added advantage of ACTA-scanning.

Brain Diseases↗
PubMed1975

Early clinical experience with the ACTA scanner.

An alternative method of computed tomography has been devised employing a new instrument, the ACTA scanner. This is a total-body scanner which permits study of virtually all body parts, since a water medium is not employed. Early clinical experience with this new method is discussed, and normal and pathological scans are presented.

Brain Diseases↗
PubMedDate not supplied

Variation of ACTA scanner numbers with the physical properties of the scanned material.

An experiment has been carried out in which an ACTA computerized axial-transverse tomographic scanner was used in a series of scans on a polystyrene phantom. Cavities in the phantom contained distilled water and various concentrations of acetic acid or ferric nitrate in aqueous solution. It is shown that the ACTA numbers generated for the low-Z acetic acid solution are proportional to the electron density of the solution, but that such is not the case for the higher-Z ferric nitrate, where photoelectric absorption is significant. The correlation of scanner numbers with electron density rather than with mass density is discussed and, as an illustrative example, the electron densities of whole blood and blood cells are calculated and the relative value is compared with the relative mass densities of the materials.

Diagnosis, Computer-Assisted↗