External radiotherapy dosimetry in nonstandard fields

Abstract

The dosimetry of the small and intensity modulated elds employed in radiotherapy, with high dose gradients involved, is a quite demanding task. The need for reliable measurements in these beams responds not only to quality assurance requirements, but also to the legal regulations of Radiotherapy (in Spain, Real Decreto 1566/1998 sobre Criterios de Calidad en Radioterapia, and also EURATOM 97/43). The complexity of modern radiotherapy techniques led to an extensive incorporation of thorough treatment dosimetric veri cation in the hospital quality assurance programs. This veri cation, previous to the treatment, is performed in order to check that the dose distributions delivered by the radiotherapy machine match the corresponding planned dose distributions within the required tolerances. One work performed in this thesis project consists in the study of di erent commercial detector arrays, devices widely employed for dosimetric treatment veri cation. The response of the detectors involved in these devices is determined in order to study the impact of the detector size, technology and layout on the measurement of intensity modulated dose distributions. The capabilities of detector arrays for the detection of uence variations is also studied, as this is one of the main objectives of treatment verication.