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Biomedical subjects

S Jayaraman

Publications and source records attributed to S Jayaraman.

139 records · Page 8Linked to original sources
PubMedDate not supplied

A Sensate Liner for personnel monitoring applications.

This program develops and demonstrates technologies useful for implementing a manageable cost effective systems approach to monitoring the medical condition of personnel by way of an instrumented uniform hereafter referred to as a Sensate Liner (SL). The SL consists of a form fitting garment which contains and interconnects sensing elements and devices to an electronics pack containing a processor and transmitter. The SL prototype requires fiber, textile, garment and sensor development. The SL textile consists of a mesh of electrically and optically conductive fibers integrated into the normal structure (woven or knitted) of fibers and yarns selected for comfort and durability. A suite of SL garment compatible embedded biological and physical sensors are then integrated into the SL. The initial SL sensor suite is selected to improve triage for combat casualties. Additional SL sensor concepts for medical monitoring will be discussed.

Aerospace Medicine↗
PubMedDate not supplied

Relationship between serum and seminal plasma prolactin in bonnet monkeys.

The relationship between serum and seminal plasma concentration of prolactin were investigated in four adult bonnet monkeys. Hyperprolactenemia induced by acute and chronic treatment with chlorpromazine showed significantly higher prolactin levels in seminal plasma on 8th and 16th day respectively, by which time the serum prolactin levels have already reached pretreatment levels. The study suggests that it may be possible to affect the sperm fertilizing capacity by pharmacologically affecting serum prolactin concentrations.

Animals↗
PubMedDate not supplied

Effect of chronic administration of Tamoxifen on fertility in male bonnet monkeys (Macaca radiata).

Administration of Tamoxifen via the Alzet pump at a rate of 50 micrograms hr-1 for 90 days in the adult male bonnet monkeys Macaca radiata had no effect on the serum testosterone concentration determined at 10 AM and 10 PM as well as total sperm count determined at 15-day intervals over a period of 260 days. However, a significant reduction in sperm motility was observed beyond 90 days up until the 225th day. Breeding studies conducted from day 90 to 260 revealed that these males were infertile.

Animals↗
PubMedDate not supplied

Influence of surface shape on tissue-air ratio for cobalt-50.

The shape of the surface of incidence could affect the scatter and change the effective tissue-air ratio (TAR) value. The curvature of the body is considerable within the large beams used for total body irradiation. The effect of the surface curvature on the effective TAR value was studied using a computational approach that sums up the differential scatter air ratios from elemental beams. It was observed that the difference between the effective TAR and the standard flat surface TAR increased with depth to reach a maximum value of about 2% around 8--11 cm depth. It decreased for larger depths, and the effect of surface shape was not perceivable beyond 18 cm depth.

Cobalt Radioisotopes↗
PubMedDate not supplied

Product representations of teletherapy dose distributions.

Product representations are frequently used for teletherapy dose distributions. For example, the dose in a central plane is often written as the product of two factors, one dependent on the depth and the other on the transverse variable. We have answered the following question: given a (two-dimensional) set of data, how closely is it possible to represent these data by a product of two such factors, and what factors would give a best-fit representation? We thus have developed a quantitative test with which to judge any proposed product representation, for a given set of data. As an example, we have applied our method in analyzing the accuracy of a model proposed by van de Geijn for representing central-plane Cobalt-60 dose data through a product representation on decrement lines intersecting the source.

Humans↗
PubMedDate not supplied

An overview of errors in line source dosimetry for gamma-ray brachytherapy.

The generally used approach for routine brachytherapy dosimetry depends on a value of source strength provided by the source supplier, the theoretical concept of exposure rate constants for different nuclides, and the applicability of inverse square law to point sources. Corrections for filtration of the radiation within the capsule of the source and attenuation in tissue medium are effected based on attenuation coefficients and data published in the literature. Therefore there is no unique or ideal way of selecting the required data and there could be a spread in the dose values derived by different users. The errors inherent in the current practice of dosimetry of linear sources in brachytherapy are discussed. If the brachytherapy sources are specified in terms of exposure rate at a distance from the source by the source suppliers, the overall uncertainty in the dosimetry at regions of clinical interest around the source could be limited to about +/- 6%.

Brachytherapy↗
PubMedDate not supplied

Can the AAPM Task Group 21 protocol lead to optimum ion chamber designs?

The recently published AAPM Task Group 21 protocol for high-energy dosimetry is complicated in that it requires the physicist to obtain the values of about a dozen different physical variables by looking them up in tables or graphs. This should be compared with the procedure of earlier protocols using the concept of a single multiplier C lambda. We have investigated how the physical principles outlined in the improved AAPM protocol could be utilized for the redesign of the therapy-level ion chambers in such a way that one can reduce the number of factors that need to be looked up in tables or graphs for the calibration of high-energy teletherapy photon beams. In our analysis presented in this paper we found that one such design could be for an ion chamber having a wall acrylic or Bakelite of a thickness not exceeding 0.1 g/cm2 and having an inner diameter of 6 mm, and used in conjunction with a cobalt-60 buildup cap of thickness 0.35 g/cm2 made of acrylic, Bakelite, or Tufnol. If a chamber of such a design is used in a water phantom, the dosimetry practically reduces to the simplicity of the former protocols of depending on a single value of energy-dependent multiplier to be obtained from a table. With the above design parameters, it becomes possible to eliminate the explicit need to incorporate the factors Pwall, Prepl, Awall, beta wall, and the variable alpha, representing the fraction of ionization due to electrons from the wall material of the chamber.

Animals↗
PubMedDate not supplied

Anterior mediastinal teratoma presenting as cardiac tamponade.

Anterior mediastinal teratoma presenting clinically as cardiac tamponade is unusual. We report the case of a 58-year-old woman, with an unremarkable prior history, who was admitted with cardiac tamponade. Emergency pericardial aspiration showed a thick, yellow fluid. Computed tomography scan of the chest was suggestive of anterior mediastinal teratoma rupturing into the pericardium. Within 24 hours, just before the planned surgery could be performed, it re-ruptured, warranting emergency surgery. Histopathology confirmed the diagnosis of a teratoma. Early surgery is recommended for even asymptomatic benign mediastinal teratomas to avoid this potentially lethal complication of rupture into the pericardial cavity, and cardiac tamponade.

Cardiac Tamponade↗
PubMedDate not supplied

Role of inhibin in polycystic ovarian syndrome.

The possible role of inhibin in the etiology of polycystic ovarian syndrome (PCO) was studied. In rats PCO was induced by thiouracil and human chorionic gonadotropin (hCG). These animals were grouped under different treatment schedules: inhibin; antibodies to inhibin; ovine follicle stimulating hormone (FSH). In rats treated with antibodies to inhibin, there was a decrease in ovarian weight concomitant with specific increase in serum FSH levels. No changes in serum luteinizing hormone (LH) and prolactin levels were observed. However, testosterone levels were significantly decreased. Histological examination of the ovaries showed a marked arrest in the cyst formation with new growing follicles. In animals treated with inhibin, testosterone levels increased without any accompanying changes in ovarian weight. The circulating levels of prolactin and LH were unaffected. A decrease in serum FSH levels was accompanied by an increase in the number of cysts. The study corroborates the hypothesis that inhibin is involved in the development of PCO syndrome. Hence, an antagonist to inhibin may prove useful for the treatment of women with this condition.

Animals↗