Electron Spin Resonance (ESR) dosimetry for clinical radiation beams.

In the last two decades the electron spin resonance (ESR) technique has been widely adopted for dosimetry of the radiation beams used in radiation therapy. In particular, alanine dosimtery is nowadays recognized as an international standard system for transfer dosimetry and for high doses. This is because among the various solid-state dosimeters the alanine ESR detectors present several advantages such as: tissue equivalence, linearity of its dose-response over a wide range, high stability of radiation induced free radicals, no destructive read-out procedure, no sample treatment before EPR signal measurement. In this presentation the main applications of ESR dosimetry for the characterization of various radiation beams used in clinical applications (such as photons, electrons, protons, charged ions and neutrons) will be reported. The possibility of improvement of ESR sensitivity to various radiation beams achieved through the use of additives will be discussed by considering the features of suitable dopants. Furthermore, since the ESR techniques is able to detect the interactions between free radicals produced by various types of radiations, recently this technique has been applied to provide information about the the linear energy transfer (LET) of the beams. These applications aimed at discriminating different radiation beams will be outlined.