RESUMEN
A linear energy transfer (LET) spectrometer based on the evaluation of particle track parameters in a chemically etched polyallyldiglycolcarbonate (PADC) track detector has been developed at our laboratory. It permits us to determine LET spectra between 10 and 700 keV microm(-1) in tissues. The LET spectra obtained permit us to calculate total dose and dose equivalent corresponding to particles with etchable tracks also. We have recently been able to verify the calibration curves used by using C, Mg, Ne, Si and Fe ion beams with different energies. The calibration curves obtained are presented and compared with those originally used, and a good correlation is found. The LET spectrometer with new calibration was used to analyse the radiation quality of the radiotherapy proton beam at the Joint Institute for Nuclear Research (JINR). The radiation quality was studied along the proton's range, particular attention being devoted to the region of the Bragg peak. It was found that the biologically weighted effective dose (BWE) reaches a value of about 1.25 at the Bragg peak region. At the beam entrance this value increases to about 1.02 due to secondary particles created through primary proton nuclear reactions in tissues.
Asunto(s)
Transferencia Lineal de Energía , Terapia de Protones , Protección Radiológica/instrumentación , Radiometría/instrumentación , Planificación de la Radioterapia Asistida por Computador/instrumentación , Radioterapia Conformacional/instrumentación , Análisis Espectral/instrumentación , Algoritmos , Carga Corporal (Radioterapia) , Diseño de Equipo , Análisis de Falla de Equipo/métodos , Humanos , Protección Radiológica/métodos , Radiometría/métodos , Dosificación Radioterapéutica , Planificación de la Radioterapia Asistida por Computador/métodos , Radioterapia Conformacional/métodos , Efectividad Biológica Relativa , Reproducibilidad de los Resultados , Medición de Riesgo/métodos , Sensibilidad y Especificidad , Análisis Espectral/métodosRESUMEN
Stacks consisting of thin CR-39 sheets sandwiched between thick lucite and water absorbers were perpendicularly bombarded by 12C ions at 200 and 244 MeV/u. Track radius distributions representing the charge composition of the fragmented beams were automatically measured by a particle track analysis system. After analysis of the nuclear charge distributions, the total charge removal cross-sections and elemental production cross-sections of fragments with atomic numbers from 5 to 3, were obtained down to the lower energies (approximately 50 and 100 MeV/u, respectively). It has been found that the measured total charge removal cross-section agrees with theoretical predictions within approximately 10% and very well with previous experiments in corresponding energy regions. Two model calculations for production of B fragment are in good agreement with our measured data while a third model overestimates it by approximately 12%. Theoretical cross-sections for Be and Li fragments differ strongly among the different models and from measured values.