Search results for " DOSIMETRY"
showing 10 items of 120 documents
Thermoluminescence Response of AlN+Y2O3 Ceramics to Sunlight and X-Ray Irradiation
2021
The present research has been sponsored by the Latvian Council of Science, Grant No. lzp-2018/1-0361. The Institute of Solid State Physics, University of Latvia as the Centre of Excellence has received funding from the European Union’s Hori-zon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-Teaming-Phase2 under grant agreement No.73950, project CAMART.2
Novel GTA-PVA Fricke gels for three-dimensional dose mapping in radiotherapy
2017
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…
Influence of the simultaneous calibration of multiple ring dosimeters on the individual absorbed dose
2021
Abstract Ring dosimeters for personal dosimetry are calibrated in accredited laboratories following ISO 4037-3 guidelines. The simultaneous irradiation of multiple dosimeters would save time, but has to be carefully studied, since the scattering conditions could change and influence the absorbed dose in nearby dosimeters. Monte Carlo simulations using PENELOPE-2014 were performed to explore the need to increase the uncertainty of H p 0 .07 in the simultaneous irradiation of three and five DXT-RAD 707H-2 (Thermo Scientific) ring dosimeters with beam qualities: N-30, N-80 and N-300. Results show that the absorbed dose in each dosimeter is compatible with each of the others and with the refere…
Application of the ESR spectrometry to evaluate the original dose in irradiated dried fruit
2008
The identification of irradiated dried fruit can be achieved by means of the electron spin resonance (ESR) spectrometry, as recommended by the European Community, since ionizing radiation induces free radicals in cellulose, a constituent of the shell. The aim of this work was to use the ESR spectrometry also as a quantitative procedure to evaluate the original dose in irradiated dried fruits, using the additive dose method. Little shell pieces, taken from nuts, chestnuts, peanuts and pistachios, were irradiated at original dose values in the range 1 to 8 kGy, and the ESR signal intensity was measured. Each specimen was then reirradiated with added doses of 1 kGy, and the ESR signal was me…
Study of the glow curves of TLD exposed to thermal neutrons.
2007
The glow curves of thermoluminescent dosimeters (TLD600, TLD700 and MCP), exposed to a mixed field of thermal neutrons and gamma photons are analysed. The fluence values of thermal neutrons used, comparable with those used in radiotherapy, allow one to define the reliability of the TLDs, in particular the most sensitive MCP, in this radiation field and to get information on the dose absorbed values. The glow curves obtained have been deconvoluted using general order kinetics and the observed differences for the different LET components have been analysed. In particular, the ratio of the n(0) parameter of two different peaks seems to allow to discriminate the different contributions of neutr…
Neutron ESR dosimetry through ammonium tartrate with low Gd content.
2014
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…
Calibration of a thermoluminescent dosimeter worn over lead aprons in fluoroscopy guided procedures
2018
Fluoroscopy guided interventional procedures provide remarkable benefits to patients. However, medical staff working near the scattered radiation field may be exposed to high cumulative equivalent doses, thus requiring shielding devices such as lead aprons and thyroid collars. In this situation, it remains an acceptable practice to derive equivalent doses to the eye lenses or other unprotected soft tissues with a dosimeter placed above these protective devices. Nevertheless, the radiation backscattered by the lead shield differs from that generated during dosimeter calibration with a water phantom. In this study, a passive personal thermoluminescent dosimeter (TLD) was modelled by means of …
MONTE CARLO SIMULATIONS OF THE RESPONSE OF ESR DOSIMETERS TO NEUTRON BEAMS
2009
Electron Spin Resonance (ESR) spectroscopy is extensively used in gamma photon dosimetry. It relies on the detection of the signal from free radicals (paramagnetic species) produced after sample irradiation. Organic materials, such as alanine and ammonium tartrate, are widely used for dosimeter preparation, thanks to the good photon sensitivity and tissue equivalence of such compounds. However, the low neutron cross section of their nuclei does not make them suitable for neutron dosimetry. Thanks to its very high neutron capture cross section and to the high Linear Energy Transfer of released particles, even small additions of gadolinium will yield large sensitivity enhancements of the dosi…
CHARACTERIZATION OF THE GAMMA DOSE COMPONENT IN THE NEUTRON FIELD OF A BNCT IRRADIATION FACILITY
2017
At the University of Pavia, a neutron irradiation facility has been constructed for preclinical in vitro and in vivo studies for BNCT. The facility is a wide channel (40 x 20 x 100 cm3) inside the graphite Thermal Column of the 250 KW research reactor TRIGA Mark II. The neutron field consists in a thermal component ranging from about 1010 and 109 cm-2s-1 along the longitudinal axis of the channel and it is uniform within 10% along the transversal axes. The fast neutron contamination (En > 1.58 keV) is more than 2 orders of magnitude lower. The gamma background coming from the core has been reduced with a 20 cm thick bismuth shield, however in the facility a gamma component is still prese…
Neutron dosimetry by means of electron spin resonance (ESR) tecnique
2012
Along with the Neutron Capture Therapy (NCT) development and with the use of thermal neutrons for radiotherapeutic purposes, many efforts have been devoted to the beam characterization in order to optimize the therapy procedures. Reliable dosimetric measurements should be able to determine the various components (neutronic and photonic) of the mixed beam usually employed for therapy. We have studied the effect of the additive such as gadolinium and 10B-boric acid on the neutron sensitivity of alanine ESR dosimeters exposed to a gamma and mixed (n, gamma) field mainly composed by thermal neutrons. We have chosen both this additive nuclei because of their very high capture cross section to th…