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Analysis of Calibration Coefficients of Plane-Parallel Markus Type Ionization Chambers Calibrated in Co-60 and Electron Beams

100%
Bulski W., Ulkowski P., Gwiazdowska B.
Polish Journal of Medical Physics And Engineering
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2007
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vol. 13
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issue 3
163-174
EN
The Polish Secondary Standard Dosimetry Laboratory is part of the IAEA/WHO network of such laboratories. The SSDLs are usually not equipped with accelerators generating high energy electron beams for calibration of dosimeters. The access to medical accelerators is seriously limited due to the heavy patient load. Therefore attempts are made to use Co-60 beams for calibration of plane parallel chambers and calculate the calibration coefficients for other radiation quality, the high energy electron beam.The Markus ionization chambers, most frequently used in Poland, were analyzed in this study. The material was composed of 36 plane parallel chambers, from 20 radiotherapy centers in Poland, calibrated at the Polish SSDL during the period of 2003-2006. Before actual calibration, a number of chamber parameters were tested: long term stability, dark current, chamber sensitivity, non-linearity of dosimeter readings. Each chamber was calibrated in two different radiation beams: a) Varian 2300 accelerator 22 MeV electron beams, beam output 1.2 cGy/MU at 300 MU/min; b) Co-60 Theratron 780/403 unit with a Cobalt-60 source of 155700 GBq (4208 Ci) activity as of 6.01.2006. A reference dosimeter Keithley Instruments Inc. 6517-A with cylindrical ionization chambers Nuclear Enterprises Technology Limited type 2571 was used as the reference standard. The methods of IAEA Code of Practice for Dosimetry TRS 398 were adopted. The long term stability was analyzed on basis of calibration coefficients of 23 Markus chambers calibrated several times during the period 1994-2002.Very small differences in calibration coefficients were detected between the two calibration methods used. They ranged between -0.3 to +0.5%, the mean value being 0.1%. A very good long term stability of calibration coefficients of Markus chambers, related to the mean value over the 7 year period, ranging between -0.5 to +0.3%, was recorded.Very small differences in the results for the two calibration methods, confirmed by small standard deviations observed, indicate that these two calibration methods in the case of Markus-type plane parallel chambers may be used alternatively.
2
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Distributed System for Noise Threat Evaluation Based on Psychoacoustic Measurements

88%
Kostek B., Czyżewski A., Kotus J., Szczodrak M.
Metrology and Measurement Systems
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2012
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issue 2
3
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The Chronic Dose Assessment of Three Critical Organs for Liver Scintigraphy with Using Cr-51

88%
Marancı Ö., Tugrul A.
Acta Physica Polonica A
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2017
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vol. 132
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issue 3
476-478
EN
In this study, a dosimetric study was observed by using Cr-51 gamma radioisotope on liver scintigraphy. In this context, the source organ is determined as liver and it is aimed the evaluation of measuring doses from source organ to selected three critical organs (thyroid, gonad, and brain). An antropomorphic torso phantom has been preferred in the experiments. The measurements of critical organs doses were examined for chronic effects. Moreover, the chronic effect of Cr-51 radioisotope on critical organs was determined as cumulative dose. Thermoluminescent dosimeters were used for chronic dose assessment. In the experiments, lithium fluoride (LiF) (TLD-100) detectors were used and they were provided from Turkish Atomic Energy Authority - Cekmece Nuclear Research and Training Center and calibrated in there. Within this study, the evaluation of the cumulative doses by using Cr-51 for three critical organs was observed with an original setup by using anthropomorphic torso phantom experimentally.
4
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Physical characteristics of photon beam from a CLINAC-DBX single energy accelerator

88%
Umbarkar R., Supe S., Pandey M., Ashok J.
Polish Journal of Medical Physics And Engineering
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2011
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vol. 17
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issue 3
143-151
EN
Commissioning beam data are treated as a reference and ultimately used by treatment planning systems, therefore, it is vitally important that the collected data are of the highest quality, in order to avoid dosimetric and patient treatment errors that may subsequently lead to a poor radiation outcome. High-energy photon and electron beams from different accelerators of the same nominal energy may have different dosimetric characteristics due to differences in target and flattening filter materials, accelerator guide and collimator designs. In the present study, clinically pertinent data for the available photon energy were investigated. For making measurements in water, first time in India, a three dimensional radiation field analyzer RFA (CRS- Scan -O-Plan) was used. For absolute dosimetry and other measurements like relative output factors, wedge factors etc., a DOSE1 electrometer (Scanditronix Wellhofer) in a white polystyrene was employed. All the measured data were utilized as an input to the ECLIPSE treatment planning system for further clinical use.
5
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Multifrequency EPR study on radiation induced centers in calcium carbonates labeled with13C

75%
Sadło J., Bugaj A., Strzelczak G., Sterniczuk M., Jaegermann Z.
Nukleonika
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2015
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vol. 60
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issue 3
429-434
EN
In calcite and aragonite, γ-irradiated at 77 K, several paramagnetic centers were generated and detected by EPR spectroscopy; in calcite, CO3− (orthorhombic symmetry, bulk and bonded to surface), CO33−, NO32−, O3−, and in aragonite CO2− (isotropic and orthorhombic symmetry) depending on the type of calcium carbonate used. For calcium carbonates enriched with 13C more detailed information about the formed radicals was possible to be obtained. In both natural (white coral) and synthetic aragonite the same radicals were identified with main differences in the properties of CO2− radicals. An application of Q-band EPR allowed to avoid the signals overlap giving the characteristics of radical anisotropy.
6
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Dosimetrical evaluation of Leksell Gamma Knife 4C radiosurgery unit

75%
Sajeev T., Mustafa M., Supe S.
Polish Journal of Medical Physics And Engineering
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2011
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vol. 17
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issue 3
105-120
EN
A number of experiments was performed using standard protocols, in order to evaluate the dosimetric accuracy of Leksell Gamma Knife 4C unit. Verification of the beam alignment has been performed for all collimators using solid plastic head phantom and Gafchromic™ type MD-55 films. The study showed a good agreement of Leksell Gammaplan calculated dose profiles with experimentally determined profiles in all three axes. Isocentric accuracy is verified using a specially machined cylindrical aluminium film holder tool made with very narrow geometric tolerances aligned between trunnions of 4 mm collimator. Considering all uncertainties in all three dimensions, the estimated accuracy of the unit was 0.1 mm. Dose rate at the centre point of the unit has been determined according to the IAEA, TRS-398 protocol, using Unidose-E (PTW-Freiburg, Germany) with a 0.125 cc ion chamber, over a period of 6 years. The study showed that the Leksell Gamma Knife 4C unit is excellent radiosurgical equipment with high accuracy and precision, which makes it possible to deliver larger doses of radiation, within the limits defined by national and international guidelines, applicable for stereotactic radiosurgery procedures.
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