Biomedical subjects
Publications and source records attributed to J D Horgan.
Laparoscopy has changed the treatment approach in the patient with a nonpalpable testis. We report a novel method of laparoscopy to diagnose an atrophic, intra-abdominal testis through a contralateral inguinal peritoneotomy.
Elderly patients with ureteropelvic junction obstruction present higher risks for operative repair than younger patients and may benefit from a less invasive approach. We review 18 patients older than 65 years who underwent endopyelotomy for a primary (8) or secondary (10) ureteropelvic junction obstruction. Average followup was 32 months (range 3 to 80). Average operating time, including cystoscopy and patient positioning, was 85 minutes. Average hospital stay was 6.3 days. No intraoperative complications were encountered. One failure occurred immediately postoperatively and the patient underwent corrective pyeloplasty. One patient has had intermittent pain but a negative Whitaker test with no evidence of obstruction. The success rate is 88%. Endopyelotomy can be considered a safe and satisfactory procedure for initial treatment of significant ureteropelvic junction obstruction in the elderly.
An improved computerized procedure involving minimal operator intervention has been developed for the automated quantitative evaluation of circumferential profiles of TI-201 myocardial perfusion scintigrams to diagnose coronary artery disease. The optimal criteria for evaluating the profiles of the left anterior oblique and anterior views have been empirically determined for both immediate and delayed scintigrams. Information from both views is combined to determine values for sensitivity and specificity. In this study, 29 patients underwent both TI-201 scintigraphy and contrast coronary angiography. The computerized quantitative procedure to interpret TI-201 scintigrams was tested against the results of coronary angiography. The values of 95% for sensitivity and 100% for specificity compare well with the results of other methods and are free of most of the variables associated with visual interpretation or operator intervention on the computer.
A computerized procedure has been developed for the generation, graphic presentation and quantitative evaluation of circumferential profiles of thallium-201 myocardial perfusion. The computer data are first filtered using a two-dimensional fast Fourier transform. The optimum criteria for evaluating the profiles of the left anterior oblique (LAO) view have been empirically determined for both rest and stress. The sensitivity of 89 percent and specificity of 75 percent compare well with the results of other methods and are free of the variables of visual interpretation.
Methods have been developed for on-line computer enhancement of a scintillation camera's myocardial images and for a graphical presentation showing relative thallium-201 activity in the myocardium. Enhancement uses fast Fourier transform techniques. The methods have been applied to multiple images obtained after stress and 4--5 hr rest. Patients with myocardial infarction and/or transient ischemia were evaluated and typical examples are presented.
Minicomputer methods were developed to enhance lesions in scintillation camera images. This study was directed towards improving the diagnostic quality of liver images. A PDP-12 digital computer was interfaced to a Pho/Gamma HP III scintillation camera and programmed to carry out two-dimensional frequency-domain analysis and processing as an on-line operation. A two-dimensional frequency spectrum is produced. An interactive program allows the operator to construct graphically a frequency-domain filter and apply it to the data matrix. The filter is optimized using the image of a known phantom and then applied unchanged to the clincial liver image. An inverse Fourier transform produces an enhances image in the spatial domain. Significant enhancement of both phantom and liver images has been obtained.
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The dynamic relationship between the follicle stimulating hormone of the hypophysis and the estrogenic hormone of the ovaries is investigated. A mather matical model for this system is proposed, which unlike previous models, includet the growing follicle as an explicit part of the model. The size of this estrogen-producing follicle is postulated as a determining factor in the periodicity of the system. Simulation of this simplified piece-wise linear model yields solutions which are persistent and periodic. In addition, the results are in good agreement with known physiological data. The results also suggest that the modeling approach is extremely useful in understanding the changes in the system's behavior caused by alterations in its parameters, whether produced by disease or therapeutic measures.
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The dynamic relationship between respiratory muscle effort and the consequent changes in lung volume is investigated. A mathematical simulation based on the structures that form the connection between these two variables makes it possible to lump the contribution from all respiratory muscles into a single time-varying driving force. When this force is applied to the system model, the appropriate lung volume pattern results. The simulation results indicate the accuracy of the model and the validity of the lumped muscle force assumption. In addition, the system model adequately describes abnormal conditions such as decreased lung compliance and increased airway resistance. The results of this simulation suggest that the modeling technique is extremely useful in describing and analyzing complex respiratory system interactions.
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The respiratory control system is treated as linear with a transmission delay between ventilation and sensing points (chemoreceptors). To the accepted variables involving body gas stores, ventilatory effects, transmission effects, and steady state pH, P(CO2), P(O2) chemoreceptor response, certain detailed analysis of the central receptors have been added. By construction of a model for medullary CO(2) receptor utilizing expected values of CNS (central nervous system) circulation, CO(2) production, and tissue-buffering effects, results of experimental observation of the effects of alteration of CSF were simulated. The inclusion of CSF effects also allowed simulation of the response to alteration in inspired CO(2), hyperventilation, and the periodic breathing with prolongation of circulation time.