Search results for "Dosimeter"
showing 10 items of 96 documents
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…
Improvement of ESR dosimetry for thermal neutron beams through the addition of gadolinium.
2007
In this paper, the addition of gadolinium is proposed as a useful tool to enhance the electron spin resonance (ESR) sensitivity of organic compounds to thermal neutrons. The target of this work is the detection, through the ESR technique, of the thermal neutron fluence in a mixed field of photons and neutrons. Gadolinium was chosen because it has a very high capture cross section to thermal neutrons; its nuclear reaction with thermal neutrons induces complex inner shell transitions that generate, besides other particles, Auger electrons, which in turn release their energy in the neighborhood (only several nanometers) of the place of reaction. Gadolinium was added to two organic molecules: a…
Power saturation of ESR signal in ammonium tartrate exposed to 60Co gamma-ray photons, electrons and protons.
2006
Abstract Marrale, M., Brai, M., Triolo, A., Bartolotta, A. and D'Oca, M. C. Power Saturation of ESR Signal in Ammonium Tartrate Exposed to 60Co γ-Ray Photons, Electrons and Protons. Radiat. Res. 166, 802–809 (2006). In this paper we present an investigation of the electron spin resonance (ESR) line shape of ammonium tartrate (AT) dosimeters exposed to radiation with different linear energy transfer (LET). We exposed our dosimeters to γ-ray photons (60Co), 7 MeV and 14 MeV initial energy electrons, and 19.3 MeV initial energy protons. The differences in the power saturation behavior of ESR spectra of AT irradiated with photons, electrons and protons could be correlated to the effective LET o…
Sensitivity of alanine dosimeters with gadolinium exposed to 6 MV photons at clinical doses.
2011
In this study we analyzed the ESR signal of alanine dosimeters with gadolinium exposed to 6 MV linear accelerator photons. We observed that the addition of gadolinium brings about an improvement in the sensitivity to photons because of its high atomic number. The experimental data indicated that the addition of gadolinium increases the sensitivity of the alanine to 6 MV photons. This enhancement was better observed at high gadolinium concentrations for which the tissue equivalence is heavily reduced. However, information about the irradiation setup and of the radiation beam features allows one to correct for this difference. Monte Carlo simulations were carried out to obtain information on …
Study of reliability of TLDs for the photon dose mapping in reactor neutron fields for BNCT
2008
Abstract Photon dose measurements in radiation fields having the proper characteristics for boron neutron capture therapy (BNCT) present several troubles. The thermal neutron flux is very high and produces a significant contribution to the response of most dosimeters. The consistency of photon dose measurements with CaF 2 :Tm and LiF:Mg, Ti thermoluminescent dosimeters has been studied. A method is described for obtaining the gamma dose with TLD-700 and some results are presented to test its reliability.
Anomalous behavior of LiF:Mg,Cu,P (TLD100H) irradiated with electron beams
2006
Abstract Thermoluminescent dosimeters of LiF:Mg,Cu,P (TLD100H) were exposed to 60Co γ -ray, protons, high energy electrons and the glow curves were analyzed. We observed an unusual behavior of the TL response of dosimeters to 7 and 14 MeV electron beam. In fact the relative amplitude between two of the five peaks (2° and 3° peaks) assumes values smaller than the unity for doses up to 5 Gy and values greater than the unity for doses equal to or greater than 10 Gy. A possible explanation of this behavior is given adopting a model of the formation of the peaks 2° and 3° and examining the different ways of energy release in matter for each beam. To perform this analysis we deconvoluted the glow…
Glow curve analysis of TLD-100H irradiated with radiation of different LET: Comparison between two theoretical method
2006
In the present paper we show the result of study on the thermoluminescent signal of LiF:Mg,Cu,P (TLD-100H) after irradiation with beams of different LET (photons, electrons and protons). Through the analysis of the glow curve it is possible to obtain information on the LET of the radiation beam. To perform this analysis we have deconvoluted the glow curves adopting general order kinetic equation for the description of the peak shape. In addition a numerical simulation has been performed to find a connection among the physical parameters of the model (OTOR) and the parameters of the empirical expression used in the analysis of the experimental data (GOK). The methodology indicate that the ki…
Production and characterization of a custom-made 228Th source with reduced neutron source strength for the Borexino experiment
2012
A custom-made 228Th source of several MBq activity was produced for the Borexino experiment for studying the external background of the detector. The aim was to reduce the unwanted neutron emission produced via (alpha,n) reactions in ceramics used typically for commercial 228Th sources. For this purpose a ThCl4 solution was converted chemically into ThO2 and embedded into a gold foil. The paper describes the production and the characterization of the custom-made source by means of gamma-activity, dose rate and neutron source strength measurements. From gamma-spectroscopic measurements it was deduced that the activity transfer from the initial solution to the final source was >91% (at 68%…
Monte Carlo and experimental derivation of TG43 dosimetric parameters for CSM-type Cs-137 sources
2004
In this study, complete dosimetric datasets for the CSM2 and CSM3 Cs-137 sources were obtained using the Monte Carlo GEANT4 code. The application of this calculation method was experimentally validated with thermoluminescent dosimetry (TLD). Functions and parameters following the TG43 formalism are presented: the dose rate constant, the radial dose functional, and the anisotropy function. In addition, to aid the quality control process on treatment planning systems, a two-dimensional (2D) rectangular dose rate table (the traditional along-away table), coherent with the TG43 dose calculation formalism, is given. The data given in this study complement existing information for both sources on…
Improvement of the LET sensitivity in ESR dosimetry for -photons and thermal neutrons through gadolinium addition
2007
Abstract We investigated the ESR response of new materials, alanine and ammonium tartrate to which gadolinium was added. The addition of gadolinium enhances sensitivity for Co 60 γ -photons because of its high atomic number ( Z = 64 ) and an enhancement of sensitivity for thermal neutrons because of its high thermal neutron cross section and high linear energy transfer (LET) secondary particles produced after the reaction with neutrons. In particular, in this paper we analyzed the microwave power saturation properties of dosimeters of alanine and ammonium tartrate with or without gadolinium exposed to different LET beams. The power saturation trends of dosimeters exposed to photons and to t…