• Journal of Radiation Industry
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• v.11 no.1
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• pp.19-25
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• 2017

It is suggested that the dose limit recommended in the Enforcement Decree of Korea's Nuclear Safety Act should not exceed 150 mSv per year for radiation workers. Recently, however, ICRP 118 report has suggested that the threshold dose of the lens should be reduced to 0.2~0.5 Gy and the mean dose should not exceed 50 mSv per year for an average of 20 mSv over 5 years. Based on these contents, $^{123}I$, $^{99m}Tc$, and $^{18}F-FDG$, which are radioisotope drugs that are used directly by radiation workers in the nuclear medicine department in Korea are expected to receive a large dose of radiation in the lens in distribution and injection jobs to administer them to patients. The ED3 Active Extremity Dosimeter was used to measure the dose of the lens in the nuclear medicine and radiation workers and how much of the dose was received per 1 mCi.

• Journal of the Korean Society of Radiology
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• v.13 no.2
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• pp.313-318
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• 2019

To improve the sensitivity, a detector using a block scintillator was developed. In the pixelated scintillator, a reflector is located between pixels to move the light generated from the scintillator to the photosensor as much as possible, and sensitivity loss occurs in the reflector portion. In order to improve the sensitivity and to have the characteristics of the pixelated scintillator, the block scintillator was processed into a scintillator in pixel form through three-dimensional laser engraving. The energy spectra and energy resolution of each pixel were measured, and sensitivity analysis of block and pixel scintillator was performed through GATE simulation. The measured global energy resolution was 20.7%, and the sensitivity was 18.5% higher than that of the pixel scintillator. When this detector is applied to imaging devices such as gamma camera and positron emission tomography, it will be possible to shorten the imaging time and reduce the dose of patient by using less radiation source.

• Journal of Radiation Industry
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• v.17 no.4
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• pp.509-518
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• 2023

The Kori Unit 1 nuclear power plant, which is planned to be dismantled after permanent shutdown, is expected to generate a large amount of various types of radioactive waste during the dismantling process. For the disposal of Very-low-level waste, which is expected to account for the largest amount of generation, the Korea Radioactive waste Agency (KORAD) is in the process of detailed design to build a 3-phase landfill disposal facility in Gyeongju. In addition, a large container is being developed to efficiently dispose of metal and concrete waste, which are mainly generated as Very low-level waste of decommissioning. In this study, based on the design characteristics of the 3-phase landfill disposal facility and the large container under development, radiation exposure dose evaluation was performed considering the normal and accident scenarios of radiation workers during operation. The direct exposure dose evaluation of workers during normal operation was performed using the MCNP computer program, and the internal and external exposure dose evaluation due to damage to the decommissioning waste package during a drop accident was performed based on the evaluation method of ICRP. For the assumed scenario, the exposure dose of worker was calculated to determine whether the exposure dose standards in the domestic nuclear safety act were satisfied. As a result of the evaluation, it was confirmed that the result was quite low, and the result that satisfied the standard limit was confirmed, and the radiational disposal suitability for the 3-phase landfill disposal facility of the large container for dismantled radioactive waste, which is currently under development, was confirmed.

• 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.

• The Korean Journal of Nuclear Medicine Technology
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• v.22 no.2
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• pp.79-83
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• 2018

Purpose $^{18}F-FDG$, which is commonly used in PET-CT examinations, is low in capacity and it is difficult to keep the amount of radioactivity busy when the specific activity is high, increasing the amount of space dose and radioactive contamination in the distribution room. Therefore, while evaluating the actual dose administered to patients during the manual dispense process, the medical institution intends to assess the usefulness of the auto dispenser by comparing the differences from the actual dose administered to the patient using the new automatic dispense. Materials and Methods From July 2016 to December 2016, 846 patients were manually administered by workers using $^{18}F-FDG$ and $^{18}F-FDG$ 906 patients were using auto dispenser from July 2017 to December 2017. Results Capacity administered to patients during the manual dispense averaged $35.41{\pm}27.79%$ compared to the recommended dose, and the auto dispenser process showed a small difference of $-2.15{\pm}3.99%$ compared to the recommended dose(p<0.05). Conclusion Working people did not have to touch radioactive medicines directly while they were busy in the auto dispenser, and because of the availability of other tasks far away, the time and distance to receive the exposure were also advantageous. It is believed that future use by many medical institutions will not only reduce the dose to patients but also help reduce the exposure dose to workers.

• The Journal of the Korea Contents Association
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• v.11 no.1
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• pp.236-244
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• 2011

Recently, the number of interventional procedures has increased dramatically as an alternative of invasive surgical procedure. The need for the quality control program of the angiographic units has also increased, because of concerns about the increased patient dose and the importance of image quality of angiographic units for the successful procedures. The purpose of this study was to propose an optimal guideline for the quality control program of the angiographic units. We reviewed domestic and international standards about medical imaging system and we evaluated the quality of 61 angiographic units in Korea with the use of NEMA 21 phantom. According to the results of our study, we propose a guideline for the quality control program of the angiographic units. Quality control program includes tube voltage test, tube current test, HVL test, image-field geometry test, spatial resolution test, low-contrast iodine detectability test, wire resolution test, phantom entrance dose test. Proposed reference levels are as follows: PAE < $\pm$ 10% in tube voltage test, PAE < $\pm$ 15% in tube current test, minimum 2.3 mmAl at 80 kVp in HVL test, minimum 'acceptable' level at image-field geometry test, 0.8 lp/mm for detector size of 34-40cm, 1.0 lp/mm for detector size of 28-33cm, 1.2 lp/mm for detector size of 22-27cm in spatial resolution test, minimum 200mg/cc in low contrast iodine detectability test, phantom entrance dose should be under 10R/min, 0.012 inch wire should be seen at static wire resolution test, and 0.022 inch wire should be seen at moving wire resolution test.

• Journal of the Korean Society of Radiology
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• v.7 no.6
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• pp.383-387
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• 2013

Diagnostic imaging systems play a critical role in obtaining anatomical images, which increases the frequency of inspection all over the world. However the likelihood that patients are exposed to relatively high radiation dose increases, which may lead to an increase of patient dose due to unnecessary radiation exposure unless appropriate management is accompanied. Thus the revised edition of IEC 60601-2-44 which is constancy tests for CT equipment which is designated as special medical equipment and is subject to safety management was studied. The results suggested the 3rd has been revised rationally in order to overcome the limitations in the 2nd by adopting clear and enhanced references, which implies the replacement of IEC 60601-2-44 2nd edition with IEC 60601-2-44 3rd will prevent the patients from the harm from improper medical equipment.

• Journal of Radiation Protection and Research
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• v.26 no.4
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• pp.385-392
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• 2001

Environmental risk factors such as ionizing radiations, heavy metals, and pesticides can cause environmental disasters when they exist in excess. The increases in use of ionizing radiation and agricultural pesticide are somewhat related to the possibility of the disaster. The risk of radiation and pesticide was evaluated by means of the single cell gel electrophoresis (SCGE) assay on the human blood lymphocytes. The lymphocytes were irradiated with $0{\sim}2.0Gy$ of $^{60}Co$ gamma ray. Another groups of lymphocytes were exposed to various concentrations of parathion. Significantly increased tail moment, which was a marker of DNA strand breaks in SCGE assay, showed a clear dose- or concentration-response relationship. Parathion of a recommended concentration for agricultural use ($1mg {\ell}^{-1}$ ) has a strong cytotoxic effect on lymphocytes, which is equivalent to damage induced by 0.1 Gy of ${\gamma}$-ray. Furthermore, $2mg{\ell}^{-1}$ of parathion can give rise to DNA damage equivalent to that induced by 0.25 Gy at which the radiation-induced damage can start to develop into clinical symptoms. The comparative results of this study can provide an experimental basis and biological information for the prevention of environmental disaster.

• Nuclear Engineering and Technology
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• v.25 no.3
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• pp.437-446
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• 1993

More realistic calculation models for evaluating man's annual intakes of radionuclides released from operating nuclear facilities were established. For the application of these models, the harvest years of food and feed crops consumed in the year of dose assessment and every year's average concentrations of a radionuclide in air and in water for the whole period of real operation had to be taken into account. KFOOD, an existing equilibrium food chain computer code for the Korean dose assessment, was modified according to the models. Sample runs of the modified code on the assumption of a constant release during 10 years' operation were made with three kinds of the input data files enabling the dose assessment in the improved method, the KFOOD method and another existing method, respectively, and the results were compared. Annual committed effective doses to Korean adult by intakes of Mn-54, Co-60, Sr-90, I-131 and Cs-137 calculated in the improved method were about 11, 2, 5, 60 and 3%, respectively, lower than the corresponding KFOOD dose. To the intakes of the radionuclides except Sr-90 evaluated in the improved method, foliar uptake contributed much more than root uptake did but, in the case of Sr-90, the result was opposite.

• The Journal of Korean Society for Radiation Therapy
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• v.32
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• pp.7-15
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• 2020

Purpose: In modern radiotherapy technology, several methods of image guided radiation therapy (IGRT) are used to deliver accurate doses to tumor target locations and normal organs, including CBCT (Cone Beam Computed Tomography) and other devices, ExacTrac System, other than CBCT equipped with linear accelerators. In previous studies comparing the two systems, positional errors were analysed rearwards using Offline-view or evaluated only with a Yaw rotation with the X, Y, and Z axes. In this study, when using CBCT and ExacTrac to perform 6 Degree of the Freedom(DoF) Online IGRT in a treatment center with two equipment, the difference between the set-up calibration values seen in each system, the time taken for patient set-up, and the radiation usefulness of the imaging device is evaluated. Materials and Methods: In order to evaluate the difference between mobile calibrations and exposure radiation dose, the glass dosimetry and Rando Phantom were used for 11 cancer patients with head circumference from March to October 2017 in order to assess the difference between mobile calibrations and the time taken from Set-up to shortly before IGRT. CBCT and ExacTrac System were used for IGRT of all patients. An average of 10 CBCT and ExacTrac images were obtained per patient during the total treatment period, and the difference in 6D Online Automation values between the two systems was calculated within the ROI setting. In this case, the area of interest designation in the image obtained from CBCT was fixed to the same anatomical structure as the image obtained through ExacTrac. The difference in positional values for the six axes (SI, AP, LR; Rotation group: Pitch, Roll, Rtn) between the two systems, the total time taken from patient set-up to just before IGRT, and exposure dose were measured and compared respectively with the RandoPhantom. Results: the set-up error in the phantom and patient was less than 1mm in the translation group and less than 1.5° in the rotation group, and the RMS values of all axes except the Rtn value were less than 1mm and 1°. The time taken to correct the set-up error in each system was an average of 256±47.6sec for IGRT using CBCT and 84±3.5sec for ExacTrac, respectively. Radiation exposure dose by IGRT per treatment was measured at 37 times higher than ExacTrac in CBCT and ExacTrac at 2.468mGy and 0.066mGy at Oral Mucosa among the 7 measurement locations in the head and neck area. Conclusion: Through 6D online automatic positioning between the CBCT and ExacTrac systems, the set-up error was found to be less than 1mm, 1.02°, including the patient's movement (random error), as well as the systematic error of the two systems. This error range is considered to be reasonable when considering that the PTV Margin is 3mm during the head and neck IMRT treatment in the present study. However, considering the changes in target and risk organs due to changes in patient weight during the treatment period, it is considered to be appropriately used in combination with CBCT.