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16 recordsLinked to original sources
PubMed1975

A novel fast neutron dosemeter based on fission chambers. Part I: Principles of operation and theoretical response in neutron therapy radiation fields.

A novel method is proposed of accurately measuring fast neutron doses of interest in radiotherapy. The technique, which utilizes calculated neutron fluence-to-kerma conversion factors, is based upon the combination of measurements with calibrated neptunium-237 and uranium-238 pulse fission chambers to obtain a response which matches the variation of kerma with neutron energy. The theoretical performance of a practical instrument has been assessed for a variety of neutron spectra to evaluate the spectrum dependence of the dosemeter. The overall systematic uncertainty using this absolute method of determining the neutron dose under charged particle equilibrium conditions is comparable to that encountered with ionization chamber techniques.

Hot Temperature↗
PubMed1976

Bone resorption measurement with unusual bone markers: critical evaluation of the method in phosphorus-deficient and calcium-deficient growing rats.

An in vivo method to evaluate bone resorption in rats, by using unusual bone seekers not dependent on renal tubular transfer, is described and a critical evaluation of the method is made. In our experimental conditions, 85Sr and 177Lu are virtually exclusively localized in bone whereas 237Np remains unchanged in different soft organs, so that the concomitant use of these markers can be used for measuring bone resorption. If osteolysis occurs 21 days after the injection of these markers, under our experimental conditions, any increase in the urinary excretion of 177Lu and 237Np represents a rise in bone resorption, whereas an increase in Sr excretion reflects both and renal tubular events. According to our bone localization studies, the enhancement of Lu and Np excretion reflects primarily an increase in cortical bone resorption localized at the endosteal (Lu) and at the periosteal (Np) surfaces respectively. In addition, strontium is considered to be the marker of mineral resorption whereas Lu and Np, under our experimental conditions, would reflect the organic bone resorption. This method is tested in phosphorus-deficient rats and in calcium-deficient rats which exhibit disturbances of calcium metabolism at both the bone and kidney levels. In agreement with previous investigations, the use of these bone markers to evaluate osteolysis shows: (a) after a 1-week phosphorus deficiency, a slight increase in cortical bone resorption with a simultaneous fall in calcium and strontium renal tubular reabsorption, and (b) after a 1-week calcium deficiency, a high rise in cortical bone resorption with a simultaneous increase in the renal tubular reabsorption of calcium and strontium.

Animals↗
PubMedDate not supplied

Measurements of actinide gut-transfer factors in humans.

Measurements have been made of the gastrointestinal absorption in humans of 239Np and 242Cm administered together in citrate media. Using five volunteers, consistent results of (2.0 +/- 0.2) x 10(-4) and (1.7 +/- 0.3) x 10(-4) were obtained for Np and Cm respectively; the quoted uncertainties are the standard errors of the means. A progress report is given of work to measure the f1 value for Pu in humans. Early work suggests an f1 value of 2 x 10(-4).

Administration, Oral↗