An analysis of patient return times for a V.A. hospital radiology department.
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Biomedical subjects
Publications and source records attributed to D E Raeside.
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Fourier analysis has been applied to the analysis of echocardiograms, with the result that anterior mitral leaflet waveforms have been classified in a manner which is unambiguous and which lends itself easily to present-day automated technology.
Chevrot's method for determining the angle between the axis of the femoral shaft and the axis of the femoral neck (the cervico-diaphyseal angle), and the angle between the axis of the femoral neck and the diacondylar plane (the anteversion angle) has been investigated and generalized. Mathematical formulae giving the anteversion and cervico-diaphyseal angles in terms of two x-ray tube angles and two measured projections of the cervico-diaphyseal angle have been derived. These formulae facilitate preparation of computer programs and tables for the routine clinical determination of the anteversion and cervico-diaphyseal angles.
Thermoluminescent dosimeters were used to estimate the dose to the thyroid and the eye for routine clinical computed tomography of the brain using an EMI CT5005 scanner (20-sec data acquisition mode, bolus covering the head). The data can be summarized by the linear relations Dt = (7.5 +/- 0.8)N millirads (8 less than or equal to N less than or equal to 18) and De = (39 +/- 5)N + (1400 +/- 200)n millirads (8 less than or equal to N less than or equal to 20, 0 less than or equal to n less than or equal to 6) where Dt is the dose to the tissue anterior to the thyroid, De is the dose to the anterior tissue of the eyelid, N is the total number of CT cuts, and n is the number of cuts in which the globe of the eye is imaged.
Schemes applicable to the automated classification of disease states identifiable through echocardiography are being studied. Initial success has been achieved in the classification of anterior mitral leaflet wave forms associated with mitral stenosis and mitral valve prolapse. These two categories were found to be readily distinguished from the normal state in a Fourier analysis framework.
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Central axis percentage depth dose values and isodose curves for the bremsstrahlung beam from a 2.5 MV Van de Graaff generator were measured with a water phantom at 100 cm target-to-surface distance. Tissue-air ratios were calculated from the central axis depth dose data. Use of the 2.5 MV percentage depth dose values are necessary for treatment planning since they are substantially larger than the values given in compilations for 2.0 MV beams.
Pattern recognition techniques have been applied to the analysis of metacarpophalangeal lengths obtained from hand radiographs. A data base consisting of healthy subjects, and subjects exhibiting achondroplasia, Down's syndrome, and Turner's syndrome was studied. A classification technique was found which effectively separates these conditions. The technique is suitable for computer automation.
An overview of Bayesian statistical decision theory is presented in the tutorial spirit. A section on fundamental principles is followed by selected applications of the Bayesian approach to parameter estimation, pattern recognition, image processing, computer-aided medical diagnosis, optimal diagnostic test selection, and radiotherapy treatment planning.
Echocardiogram analysis is treated in a pattern recognition framework. Anterior mitral leaflet waveforms are classified for the four-class problem consisting of the classes "normal," "mitral stenosis," "mitral valve prolapse," and "idiopathic hypertrophic subaortic stenosis." In addition, aortic root waveforms and left ventricular wall waveforms are classified for the two-class problem consisting of the classes "normal" and "idiopathic hypertrophic subaortic stenosis." One common method of analysis (Fourier analysis) underlies each classification scheme. Classification accuracy is sufficiently good to warrant the inference that successful automated decision-making based on the algorithms investigated is feasible.
The generation of long, high quality random number sequences for Monte Carlo simulations using minicomputers is considered. The importance of the thorough testing of Monte Carlo random number generators is emphasized. A recommendation is given to authors of Monte Carlo papers to specify their random number generator and to describe the randomness testing which that generator has undergone.
Electron-beam treatment planning for retinoblastoma was investigated and an optimal treatment plan was devised for a particular case using a new three-dimensional Monte Carlo-based treatment planning system known to be capable of correctly predicting dose perturbations caused by body surface obliquities and tissue heterogeneities. Computed tomography (CT) data files were used to construct a three-dimensional eye phantom representing the anatomy of a child's orbit. Dose distributions in sagittal, transverse, and coronal planes were predicted with 1-mm resolution. Study of these distributions led to an optimal treatment plan consisting of an anterior-lateral pair, with the anterior field being a 10-MeV, 30-mm-diam circular field, centrally blocked by a 10-mm-diam lucite lens shield and the lateral field being a 16-MeV, 30 x 25-mm D-shaped field. The anterior field delivers a therapeutic dose to the ora serrata, but it underdoses the posterior retinal surface behind the lens shield; the lateral field provides the necessary boost dose to the posterior retinal surface. An equally weighted combination of the two fields produces a dose distribution in which the entire retinal surface receives a therapeutic dose, with less than 10% of that dose being delivered to the lens, brain, and the contralateral orbit.