• Journal of Radiation Protection and Research
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• v.19 no.2
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• pp.147-156
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• 1994

On-line gamma monitoring system around KAERI-site was set up to monitor the radiation fluctuations in environment. Data on gamma exposure rates measured by the ionication chamber in the monitoring posts are transmitted to a computer of central control station with. radio telemetry transmission modem and monitored in real time. Radio telemetry transmission system is economical and reliable on handling and storing of data. This monitroing system can triger an early warning system in the event of abnormal radiation levels.

• Journal of Radiation Protection and Research
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• v.23 no.3
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• pp.139-147
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• 1998

Purpose: Tissue inhomogeneity such as lung affects tumor dose as well as transmission dose in new concept of on-line dosimetry which estimates tumor dose from transmission dose using the new algorithm. This study was carried out to confirm accuracy of correction by tissue density in tumor dose estimation utilizing transmission dose. Methods: Cork phantom (CP, density $0.202\;gm/cm^3$) having similar density with lung parenchyme and polystyrene phantom (PP, density $1.040\;gm/cm^3$) having similar density with soft tissue were used. Dose measurement was carried out under condition simulating human chest. On simulating AP-PA irradiation, PPs with 3 cm thickness were placed above and below CP, which had thickness of 5, 10, and 20 cm. On simulating lateral irradiation, 6 cm thickness of PP was placed between two 10 cm thickness CPs additional 3 cm thick PP was placed to both lateral sides. 4, 6, and 10 MV x-ray were used. Field size was in the range of $3{\times}3$ cm through $20{\times}20$ cm, and phantom-chamber distance (PCD) was 10 to 50 cm. Above result was compared with another sets of data with equivalent thickness of PP which was corrected by density. Result: When transmission dose of PP was compared with equivalent thickness of CP which was corrected with density, the average error was 0.18 (${\pm}0.27$) % for 4 MV, 0.10 (${\pm}0.43$) % for 6 MV, and 0.33 (${\pm}0.30$) % for 10 MV with CP having thickness of 5 cm. When CP was 10 cm thick, the error was 0.23 (${\pm}0.73$) %, 0.05 (${\pm}0.57$) %, and 0.04 (${\pm}0.40$) %, while for 20 cm, error was 0.55 (${\pm}0.36$) %, 0.34 (${\pm}0.27$) %, and 0.34 (${\pm}0.18$) % for corresponding energy. With lateral irradiation model, difference was 1.15 (${\pm}1.86$) %, 0.90 (${\pm}1.43$) %, and 0.86 (${\pm}1.01$) % for corresponding energy. Relatively large difference was found in case of PCD having value of 10 cm. Omitting PCD with 10 cm, the difference was reduced to 0.47 (${\pm}$1.17) %, 0.42 (${\pm}$0.96) %, and 0.55 (${\pm}$0.77) % for corresponding energy. Conclusion When tissue inhomogeneity such as lung is in tract of x-ray beam, tumor dose could be calculated from transmission dose after correction utilizing tissue density.

• Progress in Medical Physics
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• v.16 no.3
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• pp.116-124
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• 2005

Absorbed dose dosimetry protocols of high energy photon and electron beams, which are widely used and based on an air kerma calibration factors, have somewhat complex formalism and limitations for improving dosimetric accuracy due to uncertainty of the physical parameters used. Recently the IAEA and the AAPM published the absorbed dose to water-based dosimetry protocol. In this work web-based dose calibration program for IAEA TRS-398 and AAPM TG-51 protocols were developed. This program developed using the Visual C$\#$ language can be used in the internet. User selectable dosimetry protocol on the web allows the absorbed dose to water data of the two protocols at a reference point to be easily compared, and enables to conveniently manage and understand the current status of the dosimetry calibration performed at participating institutions in korea. This program and the resultant database from the web-based calibration can be useful in developing new dosimetry protocols in Korea.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1562-1565
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• 2002

속중성자 피폭 시 실리콘 다이오드 내부에서 발생되는 변위 손상을 이용한 속중성자 탐지용 PIN 다이오드를 개발하고 중성자장에서 특성변화 및 감도 실험을 통하여 성능을 검증하였다. 시뮬레이션과 다양한 구조로 제작된 소자에 대한 방사선 실험을 거쳐 집합체 형태와 개별 PIN 다이오드를 제작한 다음 중성자 반응 특성과 감도 분석을 위한 중성자 방사선 실험을 수행하였다. 여러 개의 PIN 다이오드 샘플에 대한 중성자 특성변화를 실시간으로 측정하기 위해 디지털 정전류 구동 방식의 온라인 전자적 선량계 모듈을 제작하여 사용한 실험의 결과. 본 연구에서 개발한 PIN 다이오드 소자는 중성자 방사선에 대하여 우수한 감도 특성을 갖는다는 것과 입사 중성자에 대한 방향 의존성이 거의 없다는 사실을 알 수 있었다. 그리고 이어 수행된 300여 시간의 열화실험을 통하여 본 연구에서 제작된 PIN 다이오드 소자는 중성자 탐지소자로서의 사용 가능성이 충분함을 확인할 수 있었다.

• Journal of Radiation Protection and Research
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• v.28 no.3
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• pp.255-261
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• 2003

An environmental radiation monitoring system based on high pressurized ionization chamber has been used for on-line gamma monitoring surrounding the KAERI (Korea Atomic Energy Research Institute), which transmits the dose data measured from ion chamber on the site via radio frequency to a central processing computer and stores the transmitted real-time data. Although communication using radio frequency has several advantages such as effective and economical transmission, storage, and data process, there is one main disadvantage that data loss during transmission often happens because of unexpected communication problems. It is possible to restore the loss data by off-line such as floppy disk but the simultaneous process and display of current data as well as the backup data are very difficult in the present on-line system. In this work, a new electronic circuit board and the operation software applicable to the conventional environmental radiation monitoring system are developed and the automatical synchronization of the ion chamber unit and the central processing computer is carried out every day. This system is automatically able to restore the backup data within 34 hours without additional equipments and also display together the current data as well as the transmitted backup data after checking time flag.

• 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.

• Progress in Medical Physics
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• v.27 no.1
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• pp.46-53
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• 2016

Periodical calibrations of radiation detectors are important for accurate quality assurance of therapeutic linac. The measuring instruments such as ion-chamber, thermometer, barometer, and survey meter should be calibrated periodically. Period of calibration for these instruments is suggested 6 month to one year in Korea and two years in other countries nowadays. Therefore, the determination of reasonable period for calibration is needed. In this study, we plan to utilize the results of these survey; frequent in use, how to use and stability of instruments, to determine the optimized period of calibration for the instruments in the departments of radiation oncology in Korea based on the ILAC-G24. The SurveyMonkey web-based survey tool was used and the objects of survey were 18 department of radiation oncology in university hospitals, and 15 departments were answered. The 64 questionnaires which supposed to be answered in 50 minutes were classified as the information of candidates, the thermometer, the barometer, the surveymeter, and the ion-chamber. The thermometers and the barometers were not under periodical calibration for more than half of candidates. The periods of calibration of surveymeters were 6 month to 1 year. We expect that the calibration period can be determined based on these survey results.

• The Journal of the Korea Contents Association
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• v.15 no.7
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• pp.379-388
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• 2015

Due to misbehavior of blackconsumer, companies bear higher financial burden and innocent consumers are also damaged. This study identified the characteristics of blackconsumer and their differences by demographics. Also this study scrutinizes the effects of blackconsumer characteristics on retaliation intention and self-justification. The analyses results identified three factors composing blackconsumer, namely deliberation, recidivism and persistency. Ages of 50s and 40s showed higher in persistency and 40s and 30s are higher in recidivism. Also the results showed that deliberation has a significant influence on self-justification where as recidivism and persistency have on both retaliation intention and self-justification.