GEL DOSIMETERS FOR RADIOTHERAPY APPLICATIONS: RESULTS OF A “RESEARCH PROJECT OF NATIONAL INTEREST” (PRIN)

Introduction: Gel dosimeters for three-dimensional mapping of radiotherapy doses were introduced at Yale University in the mid-1980’s. Soon after, research and development in this field also started in Italy. Early work was done at the Istituto Superiore di Sanità and at the Universities of Pisa and Milan. Several institutes now collaborate on this topic with the goal of developing new formulations of hydrogel matrices with improved characteristics of stability, sensitivity and spatial resolution compared to those of earlier Fricke-gel and polymer-gel systems. Materials and methods: Contrary to earlier gels based on natural gelling agents, such as porcine skin gelatin and/or agarose, which …

EPR/ALANINE PELLETS WITH LOW Gd CONTENT FOR NEUTRON DOSIMETRY

This paper reports on results obtained by electron paramagnetic resonance (EPR) measurements and Monte Carlo (MC) simulation on a blend of alanine added with low content of gadolinium oxide (5 % by weight) to improve the sensitivity to thermal neutron without excessively affecting tissue equivalence. The sensitivity is enhanced by this doping procedure of more an order of magnitude. The results are compared with those obtained with the addition of boric acid (50 % by weight) where boron is in its natural isotopic composition in order to produce low-cost EPR dosemeters. The gadolinium addition influences neutron sensitivity more than the boron addition. The presence of additives does not sub…

EPR RESPONSE OF PHENOLIC SOLID STATE PELLETS FOR DOSIMETRY OF RADIO- THERAPEUTIC PHOTON AND ELECTRON BEAMS

Neutron ESR dosimetry through ammonium tartrate with low Gd content.

This paper continues analyses on organic compounds for application in neutron dosimetry performed through electron spin resonance (ESR). Here, the authors present the results obtained by ESR measurements of a blend of ammonium tartrate dosemeters and gadolinium oxide (5 % by weight). The choice of low amount of Gd is due to the need of improving neutron sensitivity while not significantly influencing tissue equivalence. A study of the effect of gadolinium presence on tissue equivalence was carried out. The experiments show that the neutron sensitivity is enhanced by more than an order of magnitude even with this small additive content. Monte Carlo simulations on the increment of energy rele…

ESR response of phenol compounds for dosimetry of gamma photon beams

Abstract In the present paper we investigate the features of IRGANOX® 1076 phenols as a material for electron spin resonance (ESR) dosimetry. We experimentally analyzed the ESR response of pellets of IRGANOX® 1076 phenols irradiated with 60Co photons. The best experimental parameters (modulation amplitude and microwave power) for dosimetric applications have been obtained. The dependence of ESR signal as function of γ dose is found to be linear in the dose range studied (12–60 Gy) and the lowest measurable dose is found to be of the order of 1 Gy. The signal after irradiation is very stable in the first thirty days. From the point of view of the tissue equivalence, these materials have mass…

Novel GTA-PVA Fricke gels for three-dimensional dose mapping in radiotherapy

Abstract One of the most recent and promising developments in radiotherapy dosimetry was the introduction of 3D radiation-sensitive gels. These gels present tissue equivalent composition and density, so they also serve as phantoms, and their response is largely independent of radiation quality and dose rate. Some gels are infused with ferrous sulfate and rely on the radiation-induced oxidation of ferrous ions to ferric ions (Fricke-gels). These formulations suffer from spontaneous-oxidation and diffusion of ferric ions after irradiation; chelating agents such as xylenol-orange significantly reduces the latter. Other gel types consist of dispersed monomers, and rely on radiation-induced cros…

126. Dosimetric analysis of phenolic solid state pellets exposed to radio-therapeutic photon and electron beams through electron spin resonance technique

Abstract 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…

Study of the response of phenol compounds exposed to thermal neutrons beams for Electron Paramagnetic Resonance dosimetry

Abstract This paper reports the results regarding a new organic compound (IRGANOX ® 1076 phenols) with and without low content (5% by weight) of gadolinium oxide (Gd 2 O 3 ) for Electron Paramagnetic Resonance (EPR) dosimetry of neutron beams. The dependence of EPR signal as function of neutron dose was investigated in the fluence range studied between 10 11  cm −2 to 10 14  cm −2 . We evaluated also the effect of gadolinium on 60 Co gamma photon sensitivity of this organic compound. Our analysis showed that a low concentration of gadolinium oxide (of the order of 5% of the total mass of the dosimeter) can enhance the thermal neutron sensitivity more than 10 times with a small reduction of …