Biomedical subjects
Publications and source records attributed to R S Ledley.
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.
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.
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.
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.
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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.
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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.
The ACTA-Scanner has virtually unlimited potential in the evalution of any part of the body. The usefulness of the technique has already been shown in the appraisal of pathologies of the brain and cerebrospinal fluid cavities. The orbits and the eyeballs, the facial sinuses, and skull base lesions have also been elucidated. Tumors of the larynx, pharynx, thyroid, and parathyroid; lymphomas; and pathology of the spine and spinal cord are well within the reach of this new diagnostic methodology. Lung pathologies, such as emphysema, pneumonias, neoplasms, infarctions, pleural effusions and granulomatous diseases, and mediastinal pathology represent a challenging complex of lesions to be appraised by ACTA-scanning. For the heart, there is great potential for observing cardiac chamber size, hypertrophy of ventricular or atrial walls, and ventricular or aortic aneurysms, and possibly for recognizing the damaged myocardial tissue immediately after or some time after an infarction. The abdominal pathologies that can be studied are almost uncountable: gastric neoplasms, pancreatic cysts and stones, gallstones, neoplasms of the liver and pancreas, bowel tumors, abdominal aortic aneurysms, renal neoplasms and cysts, atrophy of the kidneys, bladder tumors, uterine tumors, ovarian cysts, and many more. Although bones and joints are adequately demonstrated by conventional x-ray techniques, there is no doubt that as the new technique is developed ACTA-grams will contribute significant information in the transverse plane, as well as in densitometric analyses. The impact of ACTA-scanning will not be limited to the diagnostic area, but will extend, at least indirectly, to general patient management and to some aspects of medical economics as well. Risk-laden, technically complex, and costly diagnostic procedures, sometimes requiring lengthy hospitalization, will in some cases be eliminated. The simple, innocuous, and noninvasive ACTA-scanning can be performed on an outpatient basis. Repeated follow-up examinations should be easily accepted by the patients, considering that this diagnostic test is carried out without discomfort. The entire field of diagnostic radiology is on the verge of revolutionary changes.
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