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Efficient reading of thermoluminescent dosimeter signals using semiconductor detectors

Sobotka Piotr, Kliś Bartłomiej, Baranowska Zuzanna, Wołoszczuk Katarzyna, Rutkowska Katarzyna, Woliński Tomasz

Nukleonika

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2020

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Vol. 65, No. 4

223--227

EN

The aim of this experimental work was to examine whether semiconductor photodetectors may be applied for the efficient reading of thermoluminescent dosimeter (TLD) signals. For this purpose, a series of experiments have been performed at the Department of Physics, Warsaw University of Technology, in cooperation with the Central Laboratory for Radiological Protection (CLOR). Specifically, the measurement system proposed here has been designed to detect a signal from TLDs that use a semiconductor detector operating in conditions analogous to those met when using commercial devices equipped with a classic photomultiplier. For the experimental tests, the TLDs were irradiated with a beam of 137Cs radiation in the accredited Laboratory for Calibration of Dosimetric and Radon Instruments. Eventually, a comparison of the results obtained with a semiconductor detector (ID120) and a commercial TLD reader with a photomultiplier tube (RADOS) were made.

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Comparison of dose distributions in target areas and organs at risk in conformal and VMAT techniques and dose verifications with the use of thermoluminescence dosimetry

Paluch-Ferszt Monika, Kozłowska Beata, Dybek Marcin

Nukleonika

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2020

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Vol. 65, No. 4

217--222

EN

The aim of the present study is to compare dose distributions and their verification in target areas and organs at risk (OAR) in conformal and volumetric modulated arc therapy (VMAT) techniques. Proper verification procedures allow the removal of the major sources of errors, such as incorrect application of a planning system, its insufficient or cursory commissioning, as well as an erroneous interpretation of the obtained results. Three target areas (head and neck, chest, and pelvic) were selected and the treatment was delivered based on plans made using collapsed cone convolution and Monte Carlo algorithms with 6-MV photon beams, adopting conformal and VMAT techniques, respectively. All the plans were prepared for the anthropomorphic phantom. Dose measurements were performed with TL detectors made of LiF phosphor doped with magnesium and titanium (LiF:Mg,Ti). This paper presents the results of TL measurements and calculated doses, as well as their deviations from the treatment planning system (TPS) in the three planned target areas. It was established that the algorithms subject to analysis differ, particularly in dose calculations for highly inhomogeneous regions (OAR). Aside from the need to achieve the dose intended for the tumour, the choice of irradiation technique in teleradiotherapy should be dictated by the degree of exposure toindividual critical organs during irradiation. While nothing deviated beyond the bounds of what is acceptable by international regulatory bodies in plans from TPS, clinically one must be more cautious with the OAR areas.

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Monte Carlo study on the gold and gadolinium nanoparticles radio-sensitizer effect in the prostate 125I seeds radiotherapy

Ghasemi-Jangjoo Amir, Ghiasi Hosein

Polish Journal of Medical Physics and Engineering

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2019

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Vol. 25, Iss. 3

165--169

EN

Monte Carlo and TL dosimetry applied to the characterization of 125I brachytherapy with a different design with other 125I seeds. In a water phantom, lattice configuration simulated with 125I seed in the center and 10 nm gold and gadolinium nan-particle filed voxels. This simulation conducted to the characterization of the nano-particles DEF in low energy and prostate tissue. To study of the prostate brachytherapy, a humanoid computational phantom developed by CT slices applied. KTMAN-2 computational phantom contains 29 organs and 19 skeletal regions and was produced from cross-sectional x-ray computed tomography (CT slices) images. The simulated seed was 125I seed having an average energy of 28.4 keV for photons, a half-life of 59.4 days. DEF factor in the seed radiation energy (28.4 keV) DEF factor was found to be two times higher for the gold nano-particles. It was revealed than gold-nano-particles posing Z about 1.24 times higher than gadolinium led to around 200% DEF increasing in the same conditions and the nano-particles size. It was concluded that in low energy sources brachytherapy, photoelectric is dominant in the presence of relative high element nanoparticles. This leads to a high dose increasing in some micro-meters and causes a dramatic dose gradient in the vicinity of a nano-particle. This dose gradient effectively kills the tumor cells in continuous low energy irradiation in the presence of a high Z material nano-scaled particle. Application of gold nano-particles in low energy brachytherapy is recommended.

4

A hand phantom for radiological measurements

Majowska B., Tuszyński M.

Nukleonika

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2005

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Vol. 50, nr 4

167-172

EN

The paper presents the construction of a hand phantom and its usefulness for radiological measurements. Situations when the hand is exposed to ionizing radiation stimulated the invention of this phantom. An extremity dosimeter was placed on the middle finger of the phantom. All measured doses are relative. The doses were compared with the dose from the extremity dosimeter. The aim of this paper was not to show values of the measured doses in legal units but the authors wanted to show the difference between the dose received by the extremity dosimeter and the doses measured on the inside of the hand phantom. High-sensitive LiF:Mg,Cu,P thermoluminescence detectors were used for the measurements because of their small size and close tissue equivalence. The hand phantom makes it possible to acquire the dose distribution on the inside of the hand. The authors suggested the calculation of the coefficients: the average hand phantom coefficient CHPhAV and the maximum hand coefficient CHPhmax from phantom measurements. The extremity dosimeter dose estimates according to the recommended coefficients allowed to obtain more reliable values.

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Improved dosimetry for BNCT by activation foils, modified thermoluminescent detectors and recombination chambers

Bilski P., Golnik N., Olko P., Pytel K., Tracz G., Tulik P., Zielczyński M.

Nukleonika

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2004

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Vol. 49, nr 2

51-56

EN

Boron neutron capture therapy (BNCT) is an experimental therapy of selected tumours, based on a nuclear reaction initiated by the capture of thermal neutron by the 10B nucleus. After 10B had been delivered selectively to tumour cells, it can be activated by neutrons to deliver locally lethal high-LET radiation. BNCT beams are complex mixed radiation fields, because of broad neutron energy range, presence of gamma contamination and necessity of precise determination of several dose components. The paper presents some results of the research project on BNCT dosimetry with activation foils, recombination chambers and TL detectors.