Search results for "Gel dosimeter"
showing 6 items of 6 documents
Diffusion coefficient of PVA Fricke gel dosimeters
2015
Fricke gel dosimeters based on various matrix has been studied for a long time as 3D dosimetric system for radiotherapy. Selfoxidation and loss of spatial resolution due to diffusion have been the main issues that have impaired the affirmation of this technique so far. As part of an Italian nation-wide research program, we were interested in develop new gel formulations that are simple, reproducible and non toxic. We studied the one dimensional diffusion coefficient of Fe3+ ions inside Fricke gel dosimeters based on a matrix of PVA cross-linked with a di-aldehyde. With a spectrophotometer equipped with a moving tray we were able to collect absorbance measurements at different positions of t…
PVA-GTA Fricke gel dosimeters exposed to clinical photons beams: Nuclear Magnetic Resonance Relaxometry and Imaging
2016
Fricke Gel (FXGs) dosimetric system is based on the radiation induced oxidation of ferrous to ferric ions. The application of Fricke gels for ionizing radiation dosimetry is continuously increasing worldwide due to their many favorable properties. However, one of their shortcomings is that ferrous and ferric ions diffuse in the gel matrix. To maintain the spatial integrity of the dose distribution, Fricke gels must be undergoing measurement within a few hours of their irradiation, so that ferric ions remain close to their point of production. Thus, the spatial integrity of the dose distribution in the Fricke gel is maintained (Schreiner, 2015). The gel matrix also contributes to the oxidati…
Correlation between ferrous ammonium sulfate concentration, sensitivity and stability of Fricke gel dosimeters exposed to clinical X-ray beams
2014
Abstract This work describes the characterization of various Fricke-Agarose-Xylenol gels (FXG) dosimeters using NMR relaxometry and MRI analysis. Using X-rays from a clinical linear accelerator (LINAC), the gels were irradiated in the dose range from 0 Gy to 20 Gy. The photon sensitivity of the FXGs was measured in terms of NMR relaxation rates; its dependence on radiation dose was determined as a function of ferrous ammonium sulfate contents (from 0.5 mM to 5 mM). Furthermore, the stability of the NMR signal was monitored over several days after irradiation. These measurements were aided by Magnetic Resonance Imaging (MRI) scans which allowed three-dimensional (3D) dose mapping. In order t…
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…
NMR relaxometry measurements of Fricke gel dosimeters exposed to neutrons
2014
Fricke infused gel matrices offer several features making them suitable for dosimetric applications; among the set here are tissue equivalence, low cost and ease of preparation. Their nuclear magnetic resonance (NMR) relaxation properties can be used as a radiation detector for the dosimetry of beams used in cancer therapy. In recent years neutron capture therapy has been resumed for the treatment of various types of cancer and it requires three-dimensional mapping of the neutron fields. In this work, we investigated this particular application through NMR relaxometry and MR imaging of Fricke gels exposed to neutrons. We analyzed both the R1 and R2 relaxation rates, which relate to the long…
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…