• Nuclear Engineering and Technology
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• v.52 no.6
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• pp.1266-1270
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• 2020

A code is developed to correct for the coincidence summing effect in detecting a voluminous gamma source, and this code is applied to a¹⁵²Eu standard source as a test case. The source is 1000 mL of liquid in a cylindrical shape. To calculate the coincidence summing effect, the cylindrical source is considered as 10(radial) × 8(height) sectional sources. For each sectional source, the peak efficiency and total efficiency are obtained by Monte Carlo simulation at each energy for 10 energies between 50 keV and 2000 keV. The efficiencies of each sector are then expressed as polynomials of gamma energy. To calculate the correction coefficients for the coincidence summing effect, the KORSUM code is used after modification. The magnitudes of correction are 4%-17% for the standard ¹⁵²Eu source measured in this study. The relative deviation of 4.7% before the coincidence correction is reduced to 0.8% after the correction is applied to the efficiency based on the measured gamma line. Hence, this study has shown that a new method has been developed that is applicable for correcting the coincidence effect in a voluminous source, and the method is applied to the measured data of a standard ¹⁵²Eu cylinder source.

• Nuclear Engineering and Technology
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• v.55 no.12
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• pp.4472-4476
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• 2023

In this study, it has been shown that the true coincidence summing correction factor can be obtained for the first time using the PHITS Monte Carlo program. Determining this correction factor using different methods and tools in each laboratory to increase the possibility of achieving high-efficiency measurement conditions is still popular in gamma-ray spectrometry. By using ¹³³Ba, ¹⁵²Eu, ¹³⁴Cs, and ⁶⁰Co point sources, the true coincidence summing factor was investigated in both near and far counting geometries for 15 different energy values. GESPECOR software was used to validate the results obtained with PHITS. A remarkable agreement was obtained between PHITS and GESPECOR, with a discrepancy of less than 3%. With this study, a new tool has been proposed to obtain the true coincidence summing factor, which is one of the significant correction factors investigated/calculated in gamma-ray spectrometric studies.

• Nuclear Engineering and Technology
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• v.54 no.5
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• pp.1754-1759
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• 2022

The activity of gamma-ray emitting nuclides is calculated assuming that each gamma-ray is detected individually; thus, the magnitude of the coincidence summing signal must be considered during activity calculations. Here, the correction factor for the coincidence summing effect was calculated, and the detection efficiencies of two HPGe detectors were compared. The CANBERRA Inc. GC4018 high-purity Ge detector provided an estimate for the peak-to-total ratio using a point source to determine the coincidence summing correction factor. The ORTEC Inc. GEM60 high-purity Ge detector uses EFFTRAN in LVis to obtain the parameters of the detector and source model and the gamma-gamma and gamma-X match estimates, in order to determine the coincidence summing correction factor. Nuclide analyses, radioactivity comparisons, and analyses of reference material samples were performed utilizing certified reference materials to accurately determine the detection efficiencies. For both Co-60 and Y-88, the detection efficiency for a point source increased by an average of at least 12-13%, whereas the detection efficiency determined using LVis increased by an average of at least 13-15%. The calculated radioactivity values of the certified reference material and reference material samples were accurate to within 3% and 6% of the measured values, respectively.

• Journal of the Korean Society of Radiology
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• v.12 no.5
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• pp.557-563
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• 2018

Coincidence summing correction effects are known to be greater as the efficiency of the detector increases and as the distance between the source and the detector increases. A point source($^{60}Co$) was used to vary the distance in the direction of the detector's center axis and in the radial direction to obtain the P/T ratio for Coincidence summing correction calibration. In this study, values for coincidence summing corrected calibration of the values in the central and radial directions were applied to the mixed volume source(450 ml CRM source) to compare the overall peak efficiency change according to P/T with Geant4. In addition, the efficiency obtained from the mapping method is applied to the seaweed, a marine sample, and the compatibility of the P/T ratio with the detector and sample very dose together. The efficiency corrected to 1,836 keV was applied to the energy zone affected by the efficiency of 500 keV and the relative error of the measured and corrected values was well matcched by the 3.2 % peak efficiency correction. As with 450 mL CRM source, the larger the volume, the lower the P/T ratio was by ${\pm}5%$. This is due to the increased scattering of gamma-rays emitted as the source becomes farther away from the detector, and this change in P/T has been confirmed to affect the Coincidence summing corrected peak efficiency.

• Nuclear Engineering and Technology
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• v.53 no.10
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• pp.3421-3430
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• 2021

Spherical NaI(Tl) detectors are used in gamma-ray spectrometry, where the gamma emissions come from the nuclei with energies in the range from a few keV up to 10 MeV. A spherical detector is aimed to give a good response to photons, which depends on their direction of travel concerning the detector center. Some distortions in the response of a gamma-ray detector with a different geometry can occur because of the non-uniform position of the source from the detector surface. The present work describes the calibration of a NaI(Tl) spherical detector using both an experimental technique and a numerical simulation method (NSM). The NSM is based on an efficiency transfer method (ETM, calculating the effective solid angle, the total efficiency, and the full-energy peak efficiency). Besides, there is a high probability for a source-to-detector distance less than 15 cm to have pulse coincidence summing (CS), which may occur when two successive photons of different energies from the same source are detected within a very short response time. Therefore, γ-γ ray CS factors are calculated numerically for a ¹⁵²Eu radioactive cylindrical source. The CS factors obtained are applied to correct the measured efficiency values for the radioactive volumetric source at different energies. The results show a good agreement between the NSM and the experimental values (after correction with the CS factors).

• Journal of the Korean Society of Radiology
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• v.15 no.6
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• pp.821-831
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• 2021

In order to calibrate energy and efficiency using the PENELOPE Code, a PENELOPE simulation was performed using a volume source. Here, we want to verify peak efficiency and usefulness by performing simultaneous measurement and correction. calculate the coincident sum correction for all volumes, first subdivide the volumes of the cylinder and the four Marinelli beakers into three heights again. Therefore, the simultaneous measurement correction coefficient in three areas and the simultaneous measurement correction coefficient for the entire volume source are calculated as output. At low energies, the j value for each source volume (50-300 ml) is small and increases significantly in the high energy range. Simulation results showed good agreement within 2.5% for all source volumes except for 50 ml and 300 ml, which were up to 4%. This means that the correction for the simultaneous measurement effect during measurement is effective. In addition. Based on this, it can be confirmed that there is an advantage to improve the detection efficiency when measuring various sources and environmental samples.

• 대한방사선방어학회:학술대회논문집
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• 2009.04a
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• pp.230-231
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• 2009

• Nuclear Medicine and Molecular Imaging
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• v.42 no.2
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• pp.112-117
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• 2008

Artifact corrections including normalization and attenuation correction were important for quantitative analysis in Nuclear Medicine Imaging. Normalization is the process of ensuring that all lines of response joining detectors in coincidence have the same effective sensitivity. Failure to account for variations in LOR sensitivity leads to bias and high-frequency artifacts in the reconstructed images. Attenuation correction is the process of the correction of attenuation phenomenon lies in the natural property that photons emitted by the radiopharmaceutical will interact with tissue and other materials as they pass through the body. In this paper, we will review the several approaches for normalization and attenuation correction strategies.

• Nuclear Engineering and Technology
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• v.48 no.3
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• pp.778-784
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• 2016

HyperGam-U was recently developed to determine uranium enrichment based on ${\gamma}$- and X-ray spectroscopy analysis. The $XK_{\alpha}$ region of the uranium spectrum contains 13 peaks for $^{235}U$ and $^{238}U$ and is used mainly for analysis. To describe the X-ray peaks, a Lorentzian broadened shape function was used, and methods were developed to reduce the number of fitting parameters for decomposing the strongly overlapping peaks using channel-energy, energy-width, and energy-efficiency calibration functions. For validation, eight certified reference material uranium samples covering uranium enrichments from 1% to 99% were measured using a high-resolution planar high-purity germanium detector and analyzed using the HyperGam-U code. When corrections for the attenuation and true coincidence summing were performed for the detection geometry in this experiment, the goodness of fit was improved by a few percent. The enrichment bias in this study did not exceed 2% compared with the certified values for all measured samples.

• Korean Journal of Remote Sensing
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• v.37 no.1
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• pp.169-176
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• 2021

The Global Space-based Inter-Calibration System (GSICS) is an international partnership sponsored by World Meteorological Organization (WMO) to continue and improve climate monitoring and to ensure consistent accuracy between observation data from meteorological satellites operating around the world. The objective for GSICS is to inter-calibration from pairs of satellites observations, which includes direct comparison of collocated Geostationary Earth Orbit (GEO)-Low Earth Orbit (LEO) observations. One of the GSICS inter-calibration methods, the Ray-matching technique, is a surrogate approach that uses matched, co-angled and co-located pixels to transfer the calibration from a well calibrated satellite sensor to another sensor. In Korea, the first GEO satellite, Communication Ocean and Meteorological Satellite (COMS), is used to participate in the GSICS program. The National Meteorological Satellite Center (NMSC), which operated COMS/MI, calculated the Radiative Transfer Model (RTM)-based GSICS coefficient coefficients. The L1P reproduced through GSICS correction coefficient showed lower RMSE and Bias than L1B without GSICS correction coefficient applied. The calculation cycles of the GSICS correction coefficients for COMS/MI visible channel are provided annual and diurnal (2, 5, 10, 14-day), but long-term evaluation according to these cycles was not performed. The purpose of this paper is to perform evaluation depending on the annual/diurnal cycles of COMS/MI GSICS correction coefficients based on the ray-matching technique using Suomi-NPP/Visible Infrared Imaging Radiometer Suite (VIIRS) data as reference data. As a result of evaluation, the diurnal cycle had a higher coincidence rate with the reference data than the annual cycle, and the 14-day diurnal cycle was the most suitable for use as the GSICS correction coefficient.