ESR/alanine dosimetry of high-energy electrons in radiotherapy.

Dosimetry with detectors of organic material and electron spin resonance (ESR) spectroscopy for readout has been developed metrologically at GSF for high-level photon radiation. The tissue-equivalent probes also appear appropriate for therapy-level dosimetry. Here, results of dose measurements are reported which were performed in a water phantom using high-energy electrons as produced by a linear accelerator. Firstly, the dose range of the ESR/alanine dosimetry system had to be extended down to around 1 Gy. On this basis the response of the alanine dosimeters was determined for electrons at different therapeutic dose levels from less than 0.5 Gy to 10 Gy. Finally depth-dose measurements were carried out for electrons with initial energies up to 21 MeV. Comparisons between ESR/alanine and ion chamber dosimetry were made performing depth-dose measurements in a water phantom to examine the agreement of both methods under field conditions