Calibration of alanine dosimeters

Abstract

In all kinds of radiation therapy it is of crucial importance to thoroughly determine the absorbed dose in the tumour, in surrounding normal tissue and in risk organs. This is done using various types of dosimeters, all with their advantages and disadvantages for different situations. Measurements of the dose distribution in a volume in terms of absolute absorbed dose are needed, for example to verify Monte Carlo calculations or clinical dose plans experimentally. To make such absolute dose measurements possible, the dosimeter requires calibration towards a dosimeter with a calibration factor that is traceable to a primary standard dosimetry laboratory. To not put the outcome of a radiation treatment at risk, the uncertainty in the absorbed dose determination at points of interest must not be higher than 5% (1 standard deviation) according to the ICRU (1976). The aim of this report is to indicate a way of calibrating two types of L-a-alanine dosimeters, an alanine/agarose gel and thin alanine films. The influence of some factors on the ESR signal from the alanine dosimeters is investigated, and suggestions are made on how to take these factors into account