Biomedical subjects

S R Domen

Publications and source records attributed to S R Domen.

4 recordsLinked to original sources

PubMed1990

Absorbed dose in water. Comparison of several methods using a liquid ionization chamber.

In the present investigation a liquid ionization chamber has been used as a transfer instrument for the quantity absorbed dose in water in a cobalt-60 gamma-ray beam. The characteristics of the liquid ionization chamber are described. The transferred dosimetric information has been compared with absorbed-dose determination using air-ionization-chamber dosimetry, water calorimetry and ferrous-sulphate dosimetry. The agreement between the different measured absorbed-dose values is very good, i.e. within 0.2%. This is an indication that the consistency in the methods used to determine absorbed dose in water is good. The impact of the new standard for air kerma in air, introduced in 1986 by the BIPM, on the air-ionization-chamber dosimetry is investigated. It is shown that any differences in the dosimetry when using the old or the new set of data cancel out for the cobalt-60 beam. The investigation also shows that the value of epsilon mG for the ferrous-sulphate dosimeter recommended in ICRU 35 for electrons can be used also in cobalt-60 beams.

Calibration↗

PubMed1980

Thermal diffusivity, specific heat, and thermal conductivity of A-150 plastic.

Some thermal properties of A-150 tissue-equivalent plastic have been determined. The results are: thermal diffusivity, 2.72 x 10(-3) cm2s-1 +/- 0.4%; specific heat, 1.72 J g-1 K-1 +/- 1.3%; and thermal conductivity, 5.3 x 10(-3) WK-1 cm-1 +/- 1.4%. The significance of the measurements for the design of a calorimeter core calibration heater is briefly described.

Calcium Fluoride↗

PubMedDate not supplied

Comparisons of calorimetric and ionometric measurements in graphite irradiated with electrons from 15 to 50 MeV.

Extensive experimental comparisons of calorimetric and ionometric measurements have been made that cover a broader range of electron energies and depths in graphite than previously reported. Electron beams of 15, 20, 25, 30, 40, and 50 MeV were used. Calorimetric absorbed-dose measurements and ionometric specific-charge measurements in air were compared in graphite at depths from 1 to 51 g/cm2. The medium was irradiated with uncollimated electron beams produced by scattering after passing through a 0.1-g/cm2 aluminum vacuum window, various thicknesses of lead foils, and air. The variation in the quotient of the two measurements was studied as a function of lead-foil thickness, depth in the medium, beam energy, foil-to-detector distance, and off-axis distance. These studies permitted the measurements to be corrected and compared with theoretical calculations that assume a broad medium irradiated with broad, parallel, monoenergetic electron beams. The overall experimental uncertainty is estimated to be 1%. The results are generally in good agreement with theoretical and experimental results of other investigators. The calorimeter received close to 1 Mrad during preliminary measurements and from 1 to 2 Mrad during the measurements reported. The results showed no detectable heat defect in graphite after prolonged periods of exposing the calorimeter to air at atmospheric pressure.

Calorimetry↗

PubMedDate not supplied

Absorbed dose water calorimeter.

Advantage was taken of the low thermal diffusivity of water and the imperviousness of polyethylene film to water to construct a calorimeter for directly measuring absorbed dose in that medium. An ultrasmall bead thermistor was sandwiched between two thin films stretched on polystyrene rings and immersed in an unregulated water bath. Ten cobalt-60 irradiation runs were made with a precision of 0.5% mean error of the mean at a dose rate of 66 mGy/s. Further development is directed toward a standard instrument that can be used in a medical therapy beam.

Calorimetry↗