Full scale applications of ESR/alanine dosimetry

The evaluation of the radiation induced free radical concentration in alanine by electron spin resonance (ESR) technique is the basis of the alanine/ESR dosimetry system. Many favourable properties such as linear response, high precision, high signal stability, nearly tissue equivalence, absence of energy and dose-rate dependence in a wide range, non destructive read-out procedure make this system not only very suitable in the high dose range applications, but also very attractive in radiotherapy. The main problem that must be solved for a wider acceptance of alanine dosimetry is related to precision which, at low doses, is dose-dependent and goes approximately from 1.5% at 5 Gy to 5% at 1 Gy. Despite this limitation, there are many cases in which alanine could be especially suitable in radiotherapy, both for patient skin dose evaluation during a treatment and for phantom studies (penumbra analysis and depth dose distribution, for instance). The Istituto Superiore di Sanita in Italy has long been active in the field of alanine dosimetry, especially for what concern its possible use in radiotherapy. In this paper some examples of application of alanine for in vivo and clinical dosimetry in photon and electron beams will be given. Some space will be also devoted to alanine dosimetry of clinical proton beams, a field in which there is nowadays much interest, due to the more and more increasing use world-wide of this new technology