RESUMO
The aim of radiotherapy treatment of cutaneous T-cell lymphoma is to irradiate the skin with an appropriately homogeneous dose distribution up to a few millimetres in depth. This can be achieved by applying one of the total skin electron irradiation techniques. An aluminium/polystyrene foam electron scattering filter was designed so that the incident beam is broadened and degraded sufficiently to achieve a mean dose uniformity in a rectangular field of 180 cm height and 40 cm width. This paper reports on the development and construction of the electron scattering filter for use with a Varian 2100C accelerator, without MLCs, with a dose uniformity, over a useful field dimension of 180 cm height and 40 cm width, of +/- 7% about the mean, and an x-ray contamination of less than 2.4% beyond a depth of 3 cm.
Assuntos
Elétrons/uso terapêutico , Filtração/instrumentação , Aceleradores de Partículas/instrumentação , Radioterapia Conformacional/instrumentação , Neoplasias Cutâneas/radioterapia , Desenho de Equipamento , Análise de Falha de Equipamento , Humanos , Radioterapia Conformacional/métodos , Rotação , Espalhamento de RadiaçãoRESUMO
The leakage radiation from electron applicators used with our linear accelerator has been measured. For the applicators 6 X 6 to 25 X 25 cm size, the leakage was measured in the plane of the patient and on the sides of the applicators with the available electron energies of 6, 9, 12, 15 and 18 MeV. The levels were significant. The highest leakage on the side was for the combination of 6 X 6-cm applicator and 9-MeV electrons (32%) and in the plane of the patient for 25 X 25-cm applicator with 18 MeV (10%) relative to the peak dose. Adding lead 1-2 mm, at appropriate locations inside the applicators has reduced the leakages to acceptable levels without affecting the beam parameters.
Assuntos
Elétrons , Aceleradores de Partículas/instrumentação , Proteção Radiológica/instrumentação , Fenômenos Biofísicos , Biofísica , Humanos , Lesões por Radiação/prevenção & controle , Radioterapia de Alta Energia/efeitos adversos , Espalhamento de RadiaçãoRESUMO
The article discusses how to use the standard utility program on Theraplan to create physical wedges which are equivalent to each of the enhanced dynamic wedges. The user must first create segmented treatment tables for each wedge, using a spreadsheet, and then convert these tables to equivalent thicknesses of an arbitrary wedge material. These thicknesses are then supplied to Theraplan. The paper discusses the agreement achieved between Theraplan and measured data, and the quality assurance procedures which should be adopted.