RESUMO
The physical responses of LiF, film and a chemical dosemeter in high energy photon and electron beams has been studied. It is shown that the response for film and the chemical dosemeter does not change significantly up to 42 MeV, while for LiF it decreases by about 10%. Analysis of calculations and measurements showed that this decrease could not be explained by existing theories.
Assuntos
Radiometria/instrumentação , Elétrons , Partículas Elementares , Dosimetria Fotográfica , Fluoretos , Lítio , Dosimetria TermoluminescenteRESUMO
L929 cells were irradiated by cyclotron-produced neutrons and by 14.8 MeV monoenergetic neutrons. For comparison cells were also irradiated by 60Co gamma rays. Following irradiation cells were treated by an equimolar solution of deoxyribonucleosides, and the effect on cell survival measured. Results show that nucleoside treatment was efficient after low-LET irradiation: gamma ray survival curves were altered by deoxyribonucleosides in terms of significantly increased extrapolation numbers only, but without Do change. Cells irradiated by neutrons from either of the two sources did not respond to nucleoside treatment, and consequently their survival curves remained unaltered. These results show that the nucleoside effect does occur after low-LET irradiation, but apparently not following high-LET irradiation. Since deoxyribonucleosides as well as other cell breakdown products are released in irradiated and necrotic tumours due to massive cell destruction, such a nucleoside effect could possibly enhance the cell survival and thus effect the result of radiotherapy. Absence of the nucleoside effect in case of high-LET irradiation may therefore be an additional potential gain from neutrons in radiotherapy.
Assuntos
Sobrevivência Celular/efeitos da radiação , Desoxirribonucleosídeos/farmacologia , Células L/efeitos da radiação , Nêutrons , Animais , Sobrevivência Celular/efeitos dos fármacos , Nêutrons Rápidos , Raios gama , Células L/efeitos dos fármacos , Camundongos , Neoplasias/radioterapia , Nêutrons/uso terapêutico , Eficiência Biológica RelativaRESUMO
We report on an investigation of the (pi(-),pi(0)pi(0)) reaction by means of measurements of the pi(0)pi(0) invariant mass distributions from pi(-) interactions on H, D, C, Al, and Cu targets at p(pi(-)) = 0.408 GeV/c. The sharp, strong peak in the pi(+)pi(-) invariant mass near 2m(pi) reported by the CHAOS Collaboration is not seen in our pi(0)pi(0) data. However, we do observe a change in the shape of the pi(0)pi(0) invariant mass spectrum for the different targets, indicating that the pi(0)pi(0) interaction diminishes in the nuclear medium as represented by nuclei D, C, Al, and Cu, compared to hydrogen.