• Journal of radiological science and technology
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• v.35 no.4
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• pp.345-352
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• 2012

As the breast cancer rate is increasing fast in Korean women, people pay more attention to mammography and number of mammography have been increasing dramatically over the last few years. Mammography is the only means to diagnose breast cancer early, but harms caused by radiation exposure shouldn't be overlooked. Therefore, it is important to calculate the radiation dose being absorbed into the breast tissue during the process of mammography for a protective measure against radiation exposure. Because it is impossible to directly measure the radiation dose being absorbed into the human body, statistical calculation methods are commonly used, and most of them are supposed to simulate the interaction between radiation and matter by describing the human body internal structure with anthropomorphic phantoms. However, a simulation using Geant4 Code of Monte Carlo Method, which is well-known as most accurate in calculating the absorbed dose inside the human body, helps calculate exact dose by recreating the anatomical human body structure as it is through the DICOM file of CT. To calculate the absorbed dose in the breast tissue, therefore, this study carried out a simulation using Geant4 Code, and by using the DICOM converted file provided by Geant4, this study changed the human body structure expressed on the CT image data into geometry needed for this simulation. Besides, this study attempted to verify if the dose calculation of Geant4 interlocking with the DICOM file is useful, by comparing the calculated dose provided by this simulation and the measured dose provided by the PTW ion chamber. As a result, under the condition of 28kVp/190mAs, the Difference(%) between the measured dose and the calculated dose was found to be 0.08 %~0.33 %, and at 28 kVp/70 mAs, the Difference(%) of dose was 0.01 %~0.16 %, both of which showed results within 2%, the effective difference range. Therefore, this study found out that calculation of the absorbed dose using Geant4 Simulation is useful in measuring the absorbed dose in the breast tissue for mammography.

• The Korean Journal of Nuclear Medicine Technology
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• v.18 no.1
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• pp.98-103
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• 2014

Purpose: The effective half life of I-131 is useful to calculate radiation dose, period of hospitalization, and exposure dose of surrounding people from patient. However, it is difficult to measure. This study estimates the effective half life in whole body and thyroid in using of value of residual radioactivity obtained from the early and delay images of Dual time I-131 whole body scan. Also, the correlations between the effective half life and serum creatinine, GFR, and administration dose were investigated in this study. Materials and Methods: The targets were 50 patients administration high dose of I-131 from February to August in 2013, having normal range of serum creatinine and over $30{\mu}IU/mL$ of TSH levels. After administration radioactive I-131, the early scan in the 3rd day and the delay scan in the 5-6th days were performed. To measure the residual radioactivity in the whole body and thyroid, ROI was set and then background radioactivity was corrected to estimate. The effective half life was estimated by calculating the ratio of measured values between the early and delay images. To compare the effective half lives of the whole body and thyroid, it was analyzed by Independent t-test, and each correlation of the effective half life, GFR, serum creatinine, and the dose of administration were analyzed by calculating the pearson's correlation coefficient. All of the analysis were determined to be statistically significant when P<0.05. Results: The effective half life of the whole body was $17.06{\pm}5.50$ hours and of the thyroid was $17.22{\pm}5.41$ hours. The two effective half life did not show significant difference (P=0.887). As the value of GFR was increased, the effective half life of whole body (r=-0.407, P=0.003) and of thyroid (r=-0.473, P=0.001) were significantly decreased; as the value of serum creatinine was increased, the effective half life of whole body (r=0.309, P=0.029) and of thyroid (r=0.371, P=0.008) were significantly increased. In the administration dose, effective half life did not have correlations. Conclusion: The effective half life of I-131 of patients treated for their thyroids were estimated only by using the images of Dual time I-131 whole body scan. Also, the correlations with the effective life, GFR, and serum creatinine were examined. This study might be utilized for a study on optimization for the period of hospitalization of patients treated by high dose of I-131 and on evaluation for internal absorbed dose of MIRD schema in application of the effective half life.

• Progress in Medical Physics
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• v.26 no.3
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• pp.160-167
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• 2015

Radiation exposure from medical diagnostic imaging procedures to patients is one of the most significant interests in diagnostic x-ray system. A miniature x-ray intraoral tube was developed for the first time in the world which can be inserted into the mouth for imaging. Dose evaluation should be carried out in order to utilize such an imaging device for clinical use. In this study, dose evaluation of the new x-ray unit was performed by 1) using a custom made in vivo Pig phantom, 2) determining exposure condition for the clinical use, and 3) measuring patient dose of the new system. On the basis of DRLs (Diagnostic Reference Level) recommended by KDFA (Korea Food & Drug Administration), the ESD (Entrance Skin Dose) and DAP (Dose Area Product) measurements for the new x-ray imaging device were designed and measured. The maximum voltage and current of the x-ray tubes used in this study were 55 kVp, and 300 mA. The active area of the detector was $72{\times}72mm$ with pixel size of $48{\mu}m$. To obtain the operating condition of the new system, pig jaw phantom images showing major tooth-associated tissues, such as clown, pulp cavity were acquired at 1 frame/sec. Changing the beam currents 20 to $80{\mu}A$, x-ray images of 50 frames were obtained for one beam current with optimum x-ray exposure setting. Pig jaw phantom images were acquired from two commercial x-ray imaging units and compared to the new x-ray device: CS 2100, Carestream Dental LLC and EXARO, HIOSSEN, Inc. Their exposure conditions were 60 kV, 7 mA, and 60 kV, 2 mA, respectively. Comparing the new x-ray device and conventional x-ray imaging units, images of the new x-ray device around teeth and their neighboring tissues turn out to be better in spite of its small x-ray field size. ESD of the new x-ray device was measured 1.369 mGy on the beam condition for the best image quality, 0.051 mAs, which is much less than DRLs recommended by IAEA (International Atomic Energy Agency) and KDFA, both. Its dose distribution in the x-ray field size was observed to be uniform with standard deviation of 5~10 %. DAP of the new x-ray device was $82.4mGy*cm^2$ less than DRL established by KDFA even though its x-ray field size was small. This study shows that the new x-ray imaging device offers better in image quality and lower radiation dose compared to the conventional intraoral units. In additions, methods and know-how for studies in x-ray features could be accumulated from this work.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.12
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• pp.4819-4825
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• 2010

In all of dental ceramics, these materials contained the radio-isotopes with natural abundance ratio. After dental treatment, remained dental ceramics in the oral cavity is caused for human internal dose. In this study, the gross beta activity levels were measured in dental materials including 22 dental ceramics, 1 resin, and 2 cements for estimation of human internal dose. In dental ceramic samples, the obtained results showed that the gross beta activity level varied between 1.317 ~ 2.935 Bq/g and the gross beta activity level was 2.379 Bq/g. And the same level for dentine, opacious dentine, translucent and enamel were 2.479 Bq/g, 2.491 Bq/g, 2.470 Bq/g and 2.069 Bq/g, respectively. The gross beta activity level of temporary resin and cements were negligible, compare to the same level of dental ceramics. The high gross beta activity level observed in opacious dentine code OD-A4 is 2.935 Bq/g thus mainly ascribable to 40K. The reduction of the radiation level of natural radio-isotopes and the improvement of the dental ceramic materials should be required for internal dose reduction.

• Journal of Radiation Protection and Research
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• v.31 no.4
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• pp.165-171
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• 2006

In Korea, a real-time effective dose measurement system is in development. The system uses 32 high-sensitivity MOSFET dosimeters to measure radiation doses at various organ locations in an anthropomorphic physical phantom. The MOSFET dosimeters are, however, mainly made of silicon and shows some degree of energy and angular dependence especially for low energy photons. This study determines the correction factors to correct for these dependences of the MOSFET dosimeters for accurate measurement of radiation doses at organ locations in the phantom. For this, first, the dose correction factors of MOSFET dosimeters were determined for the energy spectrum in the steam generator channel of the Kori Nuclear Power Plant Unit #1 by Monte Carlo simulations. Then, the results were compared with the dose correction factors from 0.652 MeV and 1.25 MeV mono-energetic photons. The difference of the dose correction factors were found very negligible $(\leq1.5%)$, which in general shows that the dose corrections factors determined from 0.662 MeV and 1.25 MeV can be in a steam general channel head of a nuclear power plant. The measured effective dose was generally found to decrease bit $\sim7%$ when we apply the dose correction factors.

• Journal of Radiation Protection and Research
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• v.29 no.2
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• pp.73-90
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• 2004

The Reg. Guide 1.109 model was reviewed against its applicability to calculating radionuclide concentrations in agricultural products for operating nuclear facilities and an improved method was proposed. The model was so modified that the radionuclides deposited since the start of operation could be considered in assessing the root uptake. Translocation factors were introduced in the equation for calculating the concentrations in edible parts due to direct plant deposition. Values specific to Korea were set up for the input parameters of the modified model. The concentrations of $^{54}Mn,\;^{60}Co,\;^{90}Sr\;and\;^{137}Cs$ in rice seeds, Chinese cabbage and radish root were calculated for various hypothetical deposition histories using the Reg. Guide 1.109 model and the modified model with parameter values in the guide and those specific to Korea put in alternately. Through comparisons among the results, it could be expected that the use of the modified model with the input of parameter values specific to Korea would result In a more resonable and realistic assessment.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.2
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• pp.195-202
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• 2018

As a rule, geological disposal is considered a safe method for final disposal of high-level radioactive waste. However, some long-lived fission products like $^{99}Tc$ and $^{129}I$ contained in spent nuclear fuel are highly mobile as less sorbing anionic species in the subsurface environment and can mainly cause exposure dose to the ecosystem by emission of beta rays in the hundreds of keV range. Therefore, if these two nuclides can be separated and converted with high efficiency into radioactively unharmful nuclides, this would have a positive effect on disposal safety. One candidate method is to transmute these two nuclides in nuclear reactors into short-lived nuclides or into stable nuclides. For this purpose, it is necessary to evaluate which reactor type is more efficient in burning these two nuclides. In this study, the simulation results of nuclear transmutation of $^{99}Tc$ and $^{129}I$ in light water reactor (PWR), heavy water reactor (CANDU) and fast neutron reactor (SFR, MET-1000) are compared and discussed.

• Journal of the Korean Society of Radiology
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• v.7 no.4
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• pp.259-264
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• 2013

Total body irradiation in the treatment of childhood leukemia, which is one of the pre-treatment with stem cell transplantation is being used, the current organization using compensators are treated. However, under the terms of the compensator organization long-term impact on the human body, it is difficult to assess directly. In this study, we use the mathematical simulation of radiation exposures body energy and the distance to the crew and the patient (source surface distance, SSD), and patients with tissue compensators change of the distance along the body of the organ doses were evaluated. As a result, the surface dose of energy 4 MV, SSD 280 cm, tissue compensators and the patient when the distance 30 cm 5.84 G / min showed the highest levels. In addition, patients with tissue compensators and the distance apart when 30 cm TBI represents the ideal dose distribution was found.

• Journal of the Korean Society of Radiology
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• v.16 no.4
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• pp.381-386
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• 2022

Non-Destruction Test (NDT) is a method to check internal defects without destroying the product. Among them, radiographic testing (RT) uses high-energy radiation, so it is very important to prevent radiation exposure of workers. Therefore, in this study, in this study, a radiation sensor structure that improves radiation detection performance compared to the existing PbI₂ and can immediately detect accidents in RT was presented. For evaluation, the conversion efficiency was analyzed in the gamma ray source through FLUKA simulation. PbI₂ with overlapping Gd₂O₂S:Tb presented in this study showed a higher radiation sensitivity from 1.22 to 3.22 times than that of non-overlapping PbI₂. This indicates that the presented sensor is suitable for use as a radiation sensor for source detection in RT.

• Journal of the Korean Society of Radiology
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• v.17 no.7
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• pp.1139-1147
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• 2023

The purpose of this paper is to present and evaluate the performance of a method for controlling the dose for optimal image acquisition while minimizing patient exposure by applying a small-sized Photomultiplier(SiPM) sensor inside a portable detector. Portable detectors have the advantage of being able to quickly access the patient's location for rapid diagnosis, but this mobility comes with the challenge of dose control. This paper presents a method to identify the dose that can have the DQE and optimal image quality of the detector through image evaluation based on IEC62220-1-1, an international standard for X-ray imaging devices, and to identify the optimal dose by matching the ADU of the image and the output of the SiPM Sensor. The Skull AP image was acquired by implementing the detector manufacturer's reference dose. The optimal dose was 342.8 µGy, and the optimal controlled dose was 148.3 µGy, which is 57 % of the manufacturer's reference dose. The Chest AP image was 81.9 µGy and the optimal controlled dose was 27.9 µGy, which is a high dose reduction effect of 66 %. In addition, the two images were analyzed by five radiologists and found to have no clinically significant difference in anatomical delineation.