• 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.

• Journal of the Korean Society of Radiology
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• v.14 no.4
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• pp.487-494
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• 2020

The distance between the source and the detector, the diameter of the detector, and the volume effect of the radiation source result in a change in solid angle at the detector entrance, which affects the determination of detection efficiency by causing a difference in path length within the detector. A typical analysis method for calculating solid angles was useful only for a source (⁶⁰Co) with a simple geometric structure, so in this experiment, the distance between the detector and the source was measured by switching on for up to 25 cm with the reference point of window cap 0.5 cm. In addition, 450 and 1000 ㎖ Marinelli beaker of standard volumetric sources were closely adhered to the detector. For circular point sources co-axial with the detector, the change in the solid angle to the distance from the detector window is equal to half the square radius of the source versus the square radius of the detector, if the resulting relationship of the calculation analysis results in the detector being less than the radius of the source. Since the solid angular difference is 0.5 the result of Monte Carlo is acceptable. The relationship between detector and source distance is shown. Solid angles have been verified to decrease rapidly with distance. Measurement and simulation results for a volumetric source show a difference of ±1.01% from a distance of 0 cm and less than 4 % when the distance is reduced to 5 and 10 cm. It can be seen that the longer distance, the smaller efficiency angle, and the exponential increase in attenuation as the energy decreases, is reflected in the calculation of efficiency. Thus, the detection efficiency has proved sufficient for the use of solid angle and Monte Carlo codes.

• Journal of Radiation Protection and Research
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• v.29 no.1
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• pp.17-23
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• 2004

In order to save time and money needed in the purchase commonly used gamma-ray standard sources, a new radioactive standard source was manufactured by the neutron activation of some regent in the research reactor HANARO. The source was manufactured with an aqueous solution by mixing and dissolving the irradiated reagents. The manufactured source was compared with a commercial standard source. It was confirmed that it could be used as an efficiency calibration source. Also, in order to compare the variation of efficiency due to the volume difference for various containers used in radioactivity assay, the efficiency variation as a function of sample volume was investigated.

• Journal of the Korean Society of Radiology
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• v.12 no.2
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• pp.123-131
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• 2018

This study compared PENELOPE with measured values from low energy peak to high energy peak to reduce peak to compton ratio and continuum background spectrum using $^{60}Co$, $^{137}Cs$ and mixed volume source. In addition, the change in backscattering and compton edge efficiency was compared with that of PENELOPE through changes in the vicinity of low energy. The results from the mixed volume source are applied to the soil samples to determine how much the minimum detection limits of the soil samples are reduced in the suppression and unsuppressed mode. The compton suppression of the low energy region of $^{60}CO$ (1,173 keV) was considerable, and the Compton edge RF for the $^{137}Cs$ (661 keV) peak was 2.8. In particular, the $^{60}Co$ source emits coincidence gamma rays of 1,173.2 keV and 1,332.5 keV, so compton inhibition was reduced by approximately 21%. RF of compton edges of 1,173 keV and 1,332 keV emitted from a $^{60}Co$ source was 3.2 and 3.4, and the peak to compton edge ratio was improved to 8: 1. And Compared with Penelope, the uncertainty was well within 2%. In compton unsuppressed mode, MDA values of 661 keV, 1,173 keV and 1,332 keV were 0.535, 0.173 and 0.136 Bq/kg, respectively, but decreased in compton suppressed mode to 0.121, 0.00826 and 0.00728 Bq/kg. Thus, Compton suppressed could reduce the background radioactivity and the radioactivity contained in the detector itself.

• 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.

• Progress in Medical Physics
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• v.22 no.4
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• pp.190-197
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• 2011

Currently, the dose distribution calculation used by commercial treatment planning systems (TPSs) for high-dose rate (HDR) brachytherapy is derived from point and line source approximation method recommended by AAPM Task Group 43 (TG-43). However, the study of Monte Carlo (MC) simulation is required in order to assess the accuracy of dose calculation around three-dimensional Ir-192 source. In this study, geometry factor was calculated using segmented sources integration method by dividing microSelectron HDR Ir-192 source into smaller parts. The Monte Carlo code (MCNPX 2.5.0) was used to calculate the dose rate $\dot{D}(r,\theta)$ at a point ($r,\theta$) away from a HDR Ir-192 source in spherical water phantom with 30 cm diameter. Finally, anisotropy function and radial dose function were calculated from obtained results. The obtained geometry factor was compared with that calculated from line source approximation. Similarly, obtained anisotropy function and radial dose function were compared with those derived from MCPT results by Williamson. The geometry factor calculated from segmented sources integration method and line source approximation was within 0.2% for $r{\geq}0.5$ cm and 1.33% for r=0.1 cm, respectively. The relative-root mean square error (R-RMSE) of anisotropy function obtained by this study and Williamson was 2.33% for r=0.25 cm and within 1% for r>0.5 cm, respectively. The R-RMSE of radial dose function was 0.46% at radial distance from 0.1 to 14.0 cm. The geometry factor acquired from segmented sources integration method and line source approximation was in good agreement for $r{\geq}0.1$ cm. However, application of segmented sources integration method seems to be valid, since this method using three-dimensional Ir-192 source provides more realistic geometry factor. The anisotropy function and radial dose function estimated from MCNPX in this study and MCPT by Williamson are in good agreement within uncertainty of Monte Carlo codes except at radial distance of r=0.25 cm. It is expected that Monte Carlo code used in this study could be applied to other sources utilized for brachytherapy.

• Journal of the Korean Society of Radiology
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• v.6 no.6
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• pp.489-493
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• 2012

Positron Annihilation Lifetime Spectroscopy is a non-destructive technique to study voids and defects in solids by the measurement of gammas from electron-positron annihilation. In this study, we measured the lifetime of CR, EPDM, NBR, all of which are widely used polymer in various fields. A conventional fast-fast coincidence system in KAERI(Korea Atomic Energy Research Institute) has been used to measure the lifetime spectra, Three lifetime components were analyzed from each lifetime spectra. According to Tao-Eldrup model equation, the size and fraction of free-volume were calculated. Mean radius and free volume fraction of CR, EPDM NBR are $0.1217nm^3$(1.9103%), $0.14780nm^3$(5.3147%), $0.1216nm^3$(2.6381%), respectively. Through these measurements, we identified the feasibility of the PAL system for polymer analysis.

• Journal of the Korean Society of Radiology
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• v.17 no.4
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• pp.531-539
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• 2023

Self-absorption is the most important factor affecting the accuracy of gamma spectroscopy measurements in environmental samples. In particular, it is affected by other factors such as the chemical composition of the sample, geometric shape, thickness, density, atomic number, distance between the sample and detector, energy of the emitted gamma photon, and humidity coefficient or percentage in the sample. To test the calibration method, a 450 ml CRM standard source (9 nuclide) Marinelli beaker was used. Five soil samples among environmental samples were measured by density by applying the corrected values. Therefore, it can be seen that the self-absorption value is more effective for somewhat large and low photon energy. In the case of environmental samples, it was confirmed that the overall energy peak efficiency through self-absorption of the source greatly depends on the density of the sample.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.4 no.3
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• pp.275-284
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• 2006

In the measurement of gamma rays emitted from the nuclide in the radioactive waste drum, to analyze the nuclide concentration accurately, it is necessary to use the proper calibration standards and to correct for the attenuation of the gamma rays. Two drums having a different density were used to analyze the nuclide concentration inside the drum in this study. After carrying out the system calibration, we measured the gamma rays emitted from the standard source inside the model drum with changing the distance between the drum and the detector. The measured values were corrected with the three kinds of gamma attenuation correction methode, as a results, the error was less than 10 % in the low density drum and less than 25 % in the high density drum. The measured activity in the short distance was more accruable than in the long distance. The transmission correction for the mass attenuation showed good results(very Low error) compared to the mean density and the differential peak correction method.

• The Korean Journal of Nuclear Medicine Technology
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• v.21 no.1
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• pp.70-75
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• 2017

Purpose Radioactive iodine thyroid uptake (RAIU) rate is an examination which determines and seeks about general functions of thyroid gland. The size of thyroid gland is normally different between each person, also patients having thyroid diseases have had a variety of size of thyroid gland compared with others. The purpose of this study will investigate about the counting rate which is effected by the geometric factors through the length and volume changes of the source in RAIU rate. Materials and Methods I-131 185 kBq ($5{\mu}Ci$) were placed in a cylindrical phantom of 0.5 cm, 1 cm, 1.5 cm, and 3 cm in diameter, respectively, and saline was added to gradually increase the length by 1 cm in the horizontal and vertical directions to give a change in volume. The source was measured 20 times for 20 seconds from a distance of 25 cm to $364.4keV{\pm}20%$ energy ROI with Captus 3000 thyroid uptake system (Capintec, NJ, USA). Results When the source was located in the transverse direction of the detector, the consequence of one-way ANOVA is that even though the length of source is increased each diameter, there is mostly no significant difference. When the source was located in the longitudinal direction and the counting rate of length 1 cm at all diameter is set to 100%, the average is 92.57% for length 2 cm, 86.1% for 3 cm, 80.69% for 4 cm, 74.82% for 5 cm, and 69.68% at 6 cm. Conclusion According to this study, it is expected that the gap of RAIU rate has been depended on the thickness of thyroid gland as well as the diameter of the beaker. We know that the change of the volume with the increase of the length of the source had less effect on the change of the counting rate. Thus, in order to reduce the error in the measurement of the counting rate with the thyroid uptake rate equipment, an accurate counting rate can be relatively measured if the counting rate which is measured is corrected by thickness or the distance between the thyroid and the thyroid uptake rate equipment is changed.