RESUMO
Tandem systems usually comprise two detectors with different radiation energy responses and are utilized to determine the effective energy of unknown radiation beams. The aim of this paper was to evaluate the influence of absorbed dose on tandem curves obtained for different TL materials. In the studied dose interval, the results demonstrate that there is no significant influence of dose on the tandem curves. Therefore, the reliability of these systems for the determination of radiation beam effective energy was confirmed.
Assuntos
Algoritmos , Radioterapia Conformacional/métodos , Eficiência Biológica Relativa , Dosimetria Termoluminescente/instrumentação , Desenho Assistido por Computador , Desenho de Equipamento , Análise de Falha de Equipamento , Humanos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Raios XRESUMO
The main objective of this study was to carry out a direct performance comparison among some known types of TLDs-three types of CaSO(4):Dy pellets, sintered Al(2)O(3) pellets, LiF:Mg,Ti (Harshaw TLD-100), CaF(2):Dy (Harshaw TLD-200) and CaF(2):Mn (Harshaw TLD-400)-in the energy and dose ranges of diagnostic radiology beams. Several dosimetric characteristics were evaluated, such as reproducibility, sensitivity, calibration curves, lower dose limits and energy dependence.
Assuntos
Manufaturas/análise , Dosimetria Termoluminescente/instrumentação , Tomografia Computadorizada por Raios X/métodos , Desenho de Equipamento , Análise de Falha de Equipamento , Teste de Materiais , Doses de Radiação , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Raios XRESUMO
Tandem systems, each formed by a pencil ionization chamber with and without a specific covering, were developed and tested in standard radiation beams. These systems were designed to be used in computed tomography radiation beams, where the half-value layer (HVL) determination is not an easy task. The behaviour of the tandem systems in diagnostic radiology showed the possibility of their use to confirm HVL values previously determined by the conventional HVL measurement method in quality control programmes. These systems also have other advantages: low cost, easy application and quick measurement procedure.
Assuntos
Tomografia Computadorizada por Raios X/métodos , Alumínio/química , Calibragem , Cobre/química , Humanos , Polimetil Metacrilato/química , Controle de Qualidade , Doses de Radiação , Radiometria , Reprodutibilidade dos Testes , Tecnologia Radiológica , Raios XRESUMO
A special parallel-plate ionization chamber was developed. The motivation for the construction of this new chamber was mainly to fulfil the need of a reference system for computed tomography standard beams in the Calibration Laboratory of IPEN. However, the chamber was tested also in standard radiation beams of mammography and conventional diagnostic radiology. The chamber was manufactured at the institute workshop, as simply and cheaply as possible. Its design differs from the common ionization chambers used in dosimetric procedures of computed tomography equipment, because it is a parallel-plate chamber instead of a cylindrical chamber. However, its dimensions and sensitive volume are very similar to those of a commercial pencil ionization chamber. The new ionization chamber was submitted to several characterization and quality control tests, showing its very good performance.
Assuntos
Mamografia/métodos , Aceleradores de Partículas , Radiometria/métodos , Biofísica/métodos , Calibragem , Relação Dose-Resposta à Radiação , Íons , Imagens de Fantasmas , Doses de Radiação , Planejamento da Radioterapia Assistida por Computador , Radioterapia de Alta Energia/instrumentação , Tecnologia Radiológica , Terapia por Raios X , Raios XRESUMO
Pencil ionization chambers were recommended for use exclusively in the computed tomography (CT) dosimetry, and, from the start, they were developed only with this application in view. In this work, we studied the behavior of a pencil ionization chamber in various radiation beams with the objective of extending its application. Stability tests were performed, and calibration coefficients were obtained for several standard radiation qualities of the therapeutical and diagnostic levels. The results show that the pencil ionization chamber can be used in several radiation beams other than those used in CT.