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Biomedical subjects

R G Thomas

Publications and source records attributed to R G Thomas.

At least 127 records · Page 7Linked to original sources
PubMed1977

Cost analysis of a laboratory information system (LIS).

The cost of building, installing, and maintaining a full hospital laboratory communication system is expensive. Using an outside accountant, our books were audited to determine the expenses in each of our major cost centers. These data are tabulated along with services provided. Although the initial expenditures are high, the actual cost per test for full service capability is somewhere between 13 and 17 cents. If viewed as a cost per patient day, the price ranges between 59 and 85 cents.

Computers↗
PubMed1977

200 kV xeroradiography in occupational exposure to silica and asbestos.

Some details of the physics of xeroradiography, and the bearing these have on films of the lung obtained by this technique, are discussed. In experiments designed to obtain useful films with a minimum of radiation exposure it was found that an exposure range of 10-30 mas at 200 kV at 1.35 m (4 1/2 ft) without a grid or air gap gave very satisfactory results. The positive model of development was considered to give more information than the negative mode. One hundred and fourteen miners who had been exposed to silica dust, asbestos dusts or both, were examined by this technique. The xeroradiographs were compared with silver halide films taken at 200 kV. The xeroradiographs were considered to be superior in several respects, especially in the delineation of vascular shadows, normal and abnormal linear opacities. Linear opacities in asbestos-exposed subjects were better shown on the xeroradiographs and were occasionally seen on these films when the 200 kV conventional film was entirely normal. Small rounded opacities of silicosis were very poorly shown on the xeroradiographs. Pleural thickening and pleural plaques may be very well demonstrated.

Asbestosis↗
PubMed1975

Accumulation and retention of 137Cs-labelled fused aluminosilicate particles by beagle dogs after repeated inhalation exposures.

A group of 12 beagle dogs was given weekly, individual, 10-min inhalation exposures to aerosols of 137Cs-labelled, fused aluminosilicate particles (AMAD approximately equal to 1.8 micron, sigmag approximately equal to 1.6). Whole-body counting was used to assess the pulmonary deposition associated with each exposure and the long-term retention after exposures. Groups of four dogs were removed from further exposures at the end of 10, 20 and 40 exposures, respectively. Two dogs in each group were sacrificed and the other two maintained for long-term retention measurements. The inhaled material was relatively insoluble in body fluids. In each of the sacrificed dogs, approximately equal to 96% of the body burden was in the lung and approximately equal to 1% in the tracheobronchial lymph nodes. The average pulmonary deposition was approximately equal to 20% of the inhaled aerosol for 10, 20 or 30 exposures, a value which was in agreement with previously reported single exposure data. Lower values observed for exposures 31 to 40 were apparently related to differences in respiratory patterns. The long-term, whole-body retentions appear to have effective half-lives ranging from 1200-1800 days in contrast to approximately equal to 400 days seen in singly exposed dogs. Possible reasons are discussed.

Aerosols↗
PubMed1975

Lung response to localized irradiation from plutonium microspheres.

Uniform spherical 10-micrometer diameter particles of ZrO2 ceramic, containing various concentrations of PuO2, have been injected into the jugular vein of Syrian hamsters with subsequent permanent lodgement in the lung capillaries. The number of particles injected has varied from 2000 to 2 000 000 and the specific activity has been from 0.16 to 59 pCi/sphere so that lung burdens range from 0.2 to 700 nCi. To date, approximately 3000 hamsters have been committed to the experiment and two-thirds have died--the expected rate for normal animals. Little biological damage has been observed, and only five primary lung tumours have been found that may be due to radiation delivered to the lung. To provide a comparison to more uniform radiation, soluble polonium has also been instilled intratracheally. Results from the microspheres suggest that localized lung irradiation alone is not sufficient cause for tumour induction and is much less hazardous than diffuse exposure.

Animals↗