Search results for "Xylenol orange"

The impact of self-oxidation on the dosimetric performance of ferrous-sulfate/xylenol-orange gels

2015

Since their introduction in the 1980’s, most of the research on ferrous-sulfate gel dosimeters has aimed at minimizing the ferric ion diffusion phenomena that blur the 3D distribution of the signal. However, equally important are the spontaneous oxidation effects, which alter the sensitivity of the gels over time. In some gels, this effect is very pronounced and must be accounted for even when production, calibration and use of the gels are separated by just a few days. In other cases, the effect is much milder, but should still be properly accounted for when gels are used over a long period a time, such as in the proposed monitoring of adaptive radiotherapy treatments. Our work examined an…

Analysis of the response of PVA-GTA Fricke-gel dosimeters with clinical magnetic resonance imaging

2018

Abstract Fricke gel dosimeters produced with a matrix of Poly-vinyl alcohol (PVA) cross-linked with glutaraldehyde (GTA) were analyzed with magnetic resonance imaging (MRI). Previous studies based on spectrophotometry showed valuable dosimetric features of these gels in terms of X-ray sensitivity and diffusion of the ferric ions produced after irradiation. In this study, MRI was performed on the gels at 1.5 T with a clinical scanner in order to optimize the acquisition parameters and obtain high contrast between irradiated and non-irradiated samples. The PVA gels were found to offer good linearity in the range of 0–10 Gy and a stable signal for several hours after irradiation. The sensitivi…

Sviluppo e Applicazioni di nuovi materiali per la dosimetria delle radiazioni ionizzanti

The Research Activities carried out during the Three-year International PhD Course in Applied Physics of the candidate Salvatore Gallo had two main topics related to dosimetry of ionizing radiations (IR): the analysis of 3D gel dosimeters and the analysis of solid state dosimeters through electron spin resonance. Both these activities are focused on a careful study of new materials for the IR Dosimetry, both in terms of physical characterization of these new materials and of the optimization of readout methods for dosimetric measurements. The study performed through various techniques such as UV-Vis absorption spectroscopy, NMR Relaxometry, Magnetic Resonance Imaging (MRI) and Electron Spin…

Gel dosimeters for radiotherapy applications

2014

Study of optical absorbance and MR relaxation of irradiated Fricke Xylenol Orange Gel Dosimeters

2016

Studies on the optical absorbance spectra of Fricke xylenol orange gel dosimeters were performed, in the wavelength range from 300 nm to 800 nm, in order to highlight some particular characteristics that can affect the achievable precision. The spectra are different mainly due to the different types of xylenol orange that was used and to a lower extent due to the different gelling agents (agarose or gelatine). The characteristic of variation of absorbance spectra versus dose, however, are similar in the various cases and can explain some peculiarities, as apparent effects of dose threshold. Changes of spectral shapes appear over the time after irradiation. Magnetic resonance measurements pe…

Study of optical absorbance and MR relaxation of Fricke xylenol orange gel dosimeters

2017

Abstract Studies on the optical absorbance spectra of Fricke xylenol orange gel dosimeters were performed, in the wavelength range from 300 nm to 800 nm, in order to highlight some particular characteristics that can affect the achievable precision. The spectra are different mainly due to the different types of xylenol orange that was used and to a lower extent due to the different gelling agents (agarose or gelatine). The characteristic of variation of absorbance spectra versus dose, however, are similar in the various cases and can explain some peculiarities, as apparent effects of dose threshold. Changes of spectral shapes appear over the time after irradiation. Magnetic resonance measur…

LOW DOSE CHARACTERIZATION OF FRICKE GEL DOSIMETERS BY OPTICAL ABSORBANCE AND MR RELAXATION METHODS

2016

Introduction Fricke gel dosimeters allow measurements of 3D dose distributions and can be an effective tool for dosimetry verifications in radiotherapy. Various authors have reported drawbacks of the gels affecting the accuracy in case of low dose measurements. Purpose This study aims at investigating such drawbacks and at establishing the conditions for an optimal use of the gels. Materials and methods Our dosimeters consist of gels infused with a Fricke ferrous sulphate solution combined with xylenol orange (XO). Two kinds of xylenol orange (XO) and two different gelling agents (gelatin from porcine skin and Agarose) were utilized. Gels are red out by light absorption techniques: images o…