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MTS-6 detectors calibration by using ²³⁹Pu-Be neutron source

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Wrzesień M., Albiniak Ł., Al-Hameed H.
Medycyna Pracy
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2017
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vol. 68
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issue 6
705-710
EN
Background Thermoluminescent detectors, type MTS-6, containing isotope ⁶Li (lithium) are sensitive in the range of thermal neutron energy; the ²³⁹Pu-Be (plutonium-and-beryllium) source emits neutrons in the energy range from 1 to 11 MeV. These seemingly contradictory elements may be combined by using the paraffin moderator, a determined density of thermal neutrons in the paraffin block and a conversion coefficient neutron flux to kerma, not forgetting the simultaneous registration of the photon radiation inseparable from the companion neutron radiation. The main aim of this work is to present the idea of calibration of thermoluminescent detectors that consist of a ⁶Li isotope, by using ²³⁹Pu-Be neutron radiation source. Material and Methods In this work, MTS-6 and MTS-7 thermoluminescent detectors and a plutonium-and-beryllium (²³⁹Pu-Be) neutron source were used. Paraffin wax fills the block, acting as a moderator. The calibration idea was based on the determination of dose equivalent rate based on the average kerma rate calculated taking into account the empirically determined function describing the density of thermal neutron flux in the paraffin block and a conversion coefficient neutron flux to kerma. Results The calculated value of the thermal neutron flux density was 1817.5 neutrons/cm²/s and the average value of kerma rate determined on this basis amounted to 244 μGy/h, and the dose equivalent rate 610 μSv/h. The calculated value allowed for the assessment of the length of time of exposure of the detectors directly in the paraffin block. Conclusions The calibration coefficient for the used batch of detectors is (6.80±0.42)×10⁻⁷ Sv/impulse. Med Pr 2017;68(6):705–710
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Calibration of thermoluminescent detectors in Hp(0.07) units by using an X-ray tube and a ¹³⁷Cs source

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Wrzesień M.
Medycyna Pracy
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2019
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vol. 70
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issue 6
669-673
EN
Background The method of measuring doses based on the thermoluminescence phenomenon is not an absolute method. For this reason, to obtain correct results, it is necessary to calibrate detectors in the known radiation field. This paper presents a method for calibrating thermoluminescent detectors used in the measurement of personal dose equivalents (Hp(0.07)) obtained by nuclear medicine facility personnel when handling the $\text{}^{99m} \text{Tc}$ radionuclide. Material and Methods The authors used self-developed high-sensitivity thermoluminescent detectors and a HF320C X-ray unit, as well as a rod phantom. Dosimeters were calibrated in accordance with the ISO 4037-3 standard. During the measurements a vial containing a $\text{}^{99m} \text{Tc}$ radionuclide with well-known activity was also used. The energy characteristics were supplemented by using a ¹³⁷Cs source (irradiator ⁶⁰Co/¹³⁷Cs). Results The value of the calibration coefficient for 118 keV energy energy was (1.90±0.02)×10⁻⁵ mSv/imp. Taking into account the correction factor specified for of 140 keV energy at 0.962, the value of the calibration coefficient for 140 keV energy was determined as (1.83±0.02)×10⁻⁵ mSv/imp. Conclusions Verification of the calibration coefficient determined for 140 keV energy carried out with a vial containing a $\text{}^{99m} \text{Tc}$ radionuclide confirmed the correctness of the procedure. Med Pr. 2019;70(6):669–73
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Absorbed doses for patients undergoing panoramic radiography, cephalometric radiography and CBCT

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Wrzesień M., Olszewski J.
International Journal of Occupational Medicine and Environmental Health
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2017
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vol. 30
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issue 5
705-713
EN
Objectives Contemporary dental radiology offers a wide spectrum of imaging methods but it also contributes to an increase in the participation of dental radiological diagnosis in the patient’s exposure to ionizing radiation. The aim of this study is to determine the absorbed doses of the brain, spinal column, thyroid and eye lens for patients during panoramic radiography, cephalometric radiography and cone beam computed tomography (CBCT). Material and Methods The thermoluminescent dosimetry and anthropomorphic phantom was used for measuring the doses. The 15 panoramic, 4 cephalometric and 4 CBCT exposures were performed by placing high-sensitivity thermoluminescent detectors (TLD) in 18 anatomical points of the phantom. Results The maximum absorbed dose recorded during performed measurements corresponds to the point representing the brainstem and it is 10 mGy. The dose value recorded by the TLD placed in the thyroid during CBCT imaging in relation to the panoramic radiography differs by a factor of 13.5. Conclusions Cone beam computed tomography, in comparison with panoramic or cephalometric imaging technique, provides higher radiation doses to the patients. Int J Occup Med Environ Health 2017;30(5):705–713
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