Dosimetric analysis of phenolic solid state pellets exposed to radio-therapeutic photon and electron beams through electron spin resonance technique=Analisi dosimetrica di composti fenolici irradiati con fasci clinici di fotoni ed elettroni tramite spettroscopia di risonanza di spin elettronico

Purpose: Among the various dosimetric techniques used for characterizing the radiation beams used in radiation therapy, the electron spin resonance (ESR) arouses increasing interest for applications in various therapy procedures. In this work we report the ESR investigation of particular phenol compounds exposed to clinical photon and electron beams [1]. Materials and methods: Pellets were produced by mixing Phenol (IRGANOX 1076® Sigma Aldrich) and paraffin (10% by weight). The irradiations of dosimeters were performed with photon and electron beams with absorbed doses ranging from 0 to 13 Gy. Basic dosimetric properties of phenolic dosimeters, such as reproducibility, dose-response, sensitivity, linearity and dose rate dependence were investigated. Finally, the dosimeters were tested by measuring the depth dose profile of a 6 MV photon beam. ESR measurements were performed through an X band spectrometer. Readout parameters were optimized to maximize the signal without excessive spectrum distortions. Results: .A satisfactory intra-batch reproducibility of the ESR signal of the manufactured dosimeters was obtained. The analysis of the ESR signal as function of absorbed dose highlights that the response of this material is linear in the investigated dose range and is independent of the beam energy. Reliable and accurate assessment of the dose was achieved, independently of the dose rate. The minimum detectable dose was evaluated equal to approximately 0.6 Gy as effect to the presence of a no-negligible background signal that deserves further investigations. Conclusion: The observed features, along with the tissue-equivalence of IRGANOX 1076® and the stability of the ESR signal, make these dosimeters promising materials for ESR dosimetric applications in radiotherapy.