• 치과방사선
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• 제29권1호
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• pp.255-260
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• 1999

Purpose: The objective of this study was to evaluate the possibility of substitution of the zonography for the full-mouth periapical radiography in aspect of radiation protection. Materials and Methods: Rando phantom and LiF TLD chips were used for dosimetry. The absorbed doses at brain, skin above the TMJ. parotid gland. bone marrow in the mandibular body. and thyroid gland during the full-mouth periapical radiography. panoramic radiography. and zonography were measured. Resul ts: From the zonography. the absorbed doses to the brain. the skin over the TMJ. and the parotid gland were relatively high. but the absorbed doses to the bone marrow in the mandibular body and. especially. the thyroid gland were very low. Conclusion: The zonography can be an alternative to the full-mouth periapical radiography in aspect of radiation protection.

• Journal of Radiation Protection and Research
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• 제39권1호
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• pp.1-6
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• 2014

원전에서는 방사성핵종의 체내 섭취에 따른 작업종사자의 내부 방사능을 측정하기 위하여 전신계측기(WBC)를 이용하고 있다. 이 계측기는 인체 내 방사성핵종의 침적위치를 고려하여 다양한 측정 모드를 선택하여 측정할 수 있으나, 대부분 전신 모드를 적용하고 있다. 그런데 전신 모드를 적용한 내부방사능 측정값은 WBC 측정 모드 중에서 가장 보수적인 값을 나타내는 특성이 있고, 따라서 내부피폭 방사선량이 과대평가되는 문제점이 있다. 이러한 문제점을 해결하기 위해 WBC, 팬텀, 표준 방사선원을 이용하여 WBC의 측정 모드별 방사능측정 실험을 수행하였다. 이 결과에 대해 통계적 분석방법을 적용하여 WBC의 상부 및 하부 검출기 계측비율에 따라 WBC의 측정 모드를 선정할 수 있는 정량적인 기준을 제시하였다.

• Journal of Radiation Protection and Research
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• 제41권3호
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• pp.222-228
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• 2016

Background: We are developing a small size dosimeter for dose estimation in particle therapies. The developed dosimeter is an optical fiber based dosimeter mounting an radiation induced luminescence material, such as an OSL or a scintillator, at a tip. These materials generally suffer from the quenching effect under high LET particle irradiation. Materials and Methods: We fabricated two types of the small size dosimeters. They used an OSL material Eu:BaFBr and a BGO scintillator. Carbon ions were irradiated into the fabricated dosimeters at Heavy Ion Medical Accelerator in Chiba (HIMAC). The small size dosimeters were set behind the water equivalent acrylic phantom. Bragg peak was observed by changing the phantom thickness. An ion chamber was also placed near the small size dosimeters as a reference. Results and Discussion: Eu:BaFBr and BGO dosimeters showed a Bragg peak at the same thickness as the ion chamber. Under high LET particle irradiation, the response of the luminescence-based small size dosimeters deteriorated compared with that of the ion chamber due to the quenching effect. We confirmed the luminescence efficiency of Eu:BaFBr and BGO decrease with the LET. The reduction coefficient of luminescence efficiency was different between the BGO and the Eu:BaFBr. The LET can be determined from the luminescence ratio between Eu:BaFBr and BGO, and the dosimeter response can be corrected. Conclusion: We evaluated the LET dependence of the luminescence efficiency of the BGO and Eu:BaFBr as the quenching effect. We propose and discuss the correction of the quenching effect using the signal intensity ratio of the both materials. Although the correction precision is not sufficient, feasibility of the proposed correction method is proved through basic experiments.

• Journal of Radiation Protection and Research
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• 제43권1호
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• pp.1-9
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• 2018

Background: In this study, we investigate the image quality of virtual monochromatic images synthesized from dual-energy computed tomography (DECT) at voltages of 80/140 kV and 100/140 kV. Materials and Methods: Virtual monochromatic images of a phantom are synthesized from DECT scans from 40 to 70 keV in steps of 1 keV under the two combinations of tube voltages. The dose allocation of dual-energy (DE) scan is 50% for both low- and high-energy tubes. The virtual monochromatic images are compared to single-energy (SE) images at the same radiation dose. In the DE images, noise is reduced using the 100/140 kV scan at the optimal monochromatic energy. Virtual monochromatic images are reconstructed from 40 to 70 keV in 1-keV increments and analyzed using two quality indexes: noise and contrast-to-noise ratio (CNR). Results and Discussion: The DE scan mode with the 100/140 kV protocol achieved a better maximum CNR compared to the 80/140 kV protocol for various materials, except for adipose and brain. Image noise is reduced with the 100/140 kV protocol. The CNR values of DE with the 100/140 kV protocol is similar to or higher than that of SE at 120 kV at the same radiation dose. Furthermore, the maximum CNR with the 100/140 kV protocol is similar to or higher than that of the SE scan at 120 kV. Conclusion: It was found that the CNR achieved with the 100/140 kV protocol was better than that with the 80/140 kV protocol at optimal monochromatic energies. Virtual monochromatic imaging using the 100/140 kV protocol could be considered for application in breast, brain, lung, liver, and bone CT in accordance with the CNR results.

• Journal of Radiation Protection and Research
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• 제13권2호
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• pp.21-28
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• 1988

LiF : PTEE를 사용하여 중경 X-선(HVL : 0,29, 0.84, 1.60, 2.62mmCu) 영역에 대한 수중 흡수선량을 측정 해석하였다. 이때 선량계 (0.4mm ${\times}\;{\phi}$12.5mm, hot-pressed LiF TLD-700)는 루사이트로 둘러 싸여 있고 물의 흡수선량은 각각의 TL출력 값에 Burlin의 공동이론을 적용하여 해석하였다. 그 결과 물 팬텀 속 깊이 5cm에서 흡수선량률의 측정 오차는 최대 ${\pm}5%$로 나타났다. 이 측정값을 측정 오차가 ${\pm}2%$의 간접절대측정방법인 이온화법에 의한 측정값과 비교한 결과 두 값의 차이는 LiF : PTFE의 측정오차 범위 내에서 일치하였다. 이와같은 결과로 LiF : PTFE를 이용한 수중 흡수선량 측정의 신뢰성을 확인할 수 있게 되었으며 이는 중경 X-선 영역에 대한 선량당량 평가의 근거로 활용 될 수 있을 것이다.

• Journal of Radiation Protection and Research
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• 제45권4호
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• pp.171-177
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• 2020

Background: This study aims to determine the effective atomic number (Zeff) from dual-energy image sets obtained using a conventional computed tomography (CT) simulator. The estimated Zeff can be used for deriving the stopping power and material decomposition of CT images, thereby improving dose calculations in radiation therapy. Materials and Methods: An electron-density phantom was scanned using Philips Brilliance CT Big Bore at 80 and 140 kVp. The estimated Zeff values were compared with those obtained using the calibration phantom by applying the Rutherford, Schneider, and Joshi methods. The fitting parameters were optimized using the nonlinear least squares regression algorithm. The fitting curve and mass attenuation data were obtained from the National Institute of Standards and Technology. The fitting parameters obtained from stopping power and material decomposition of CT images, were validated by estimating the residual errors between the reference and calculated Zeff values. Next, the calculation accuracy of Zeff was evaluated by comparing the calculated values with the reference Zeff values of insert plugs. The exposure levels of patients under additional CT scanning at 80, 120, and 140 kVp were evaluated by measuring the weighted CT dose index (CTDIw). Results and Discussion: The residual errors of the fitting parameters were lower than 2%. The best and worst Zeff values were obtained using the Schneider and Joshi methods, respectively. The maximum differences between the reference and calculated values were 11.3% (for lung during inhalation), 4.7% (for adipose tissue), and 9.8% (for lung during inhalation) when applying the Rutherford, Schneider, and Joshi methods, respectively. Under dual-energy scanning (80 and 140 kVp), the patient exposure level was approximately twice that in general single-energy scanning (120 kVp). Conclusion: Zeff was calculated from two image sets scanned by conventional single-energy CT simulator. The results obtained using three different methods were compared. The Zeff calculation based on single-energy exhibited appropriate feasibility.

• 한국방사선학회논문지
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• 제16권4호
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• pp.471-476
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• 2022

전립샘암의 방사선치료법인 3D CRT와 IMRT 5 portals, IMRT 9 portals에서 정상장기인 대장과 갑상샘의 광중성자 선량 피폭으로 인하여 암이 발생할 확률을 연구하고자 한다. 전립샘암 총 처방선량 6600 cGy로 1회당 220 cGy, 총 횟수는 30회의 분할조사를 적용하였다. 실험에 사용한 의료용 선형가속기의 치료테이블(couch)위에 Rando phantom을 setup 한 후에 phantom의 대장, 갑상샘의 해당부위에 중성자 광자극발광선량계 (Optically stimulated luminescence albedo neutron dosimeter)를 위치시켜 측정하였다. 전립샘암 3D CRT시 정상장기인 대장과 갑상샘의 광중성자 선량으로 인한 2차 암의 발생확률은 10,000명 당 1.8명 이었다. 그리고 IMRT 5 portals은 10,000명 당 8.7명으로, 3D CRT에 비해서 약 5배 컸다. IMRT 9 portals는 1,000명 당 1.2명이 암이 발생할 확률이 있음의 결과를 도출하였다. 본 연구를 바탕으로 방사선 치료 시 발생하는 광중성자 선량으로 인하여 2차 방사선 피폭선량의 위험성을 연구하여, 향후 방사선의 확률적 영향과 방사선 방호에 관련하여 유용한 자료로 활용될 것으로 사료된다.

• 대한치과의사협회지
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• 제58권7호
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• pp.388-397
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• 2020

Objective: The purpose of the study was to calculate the effective and absorbed organ doses of cone-beam computed tomography (CBCT) in pediatric patient using personal computer-based Monte Carlo (PCXMC) software and to compare them with those measured using thermoluminescent dosimeters (TLDs) and anthropomorphic phantom. Materials and Methods: Alphard VEGA CBCT scanner was used for this study. A large field of view (FOV) (20.0 cm × 17.9 cm) was selected because it is a commonly used FOV for orthodontic analyses in pediatric patients. Ionization chamber of dose-area product (DAP) meter was located at the tube side of CBCT scanner. With the clinical exposure settings for a 10-year-old patient, DAP value was measured at the scout and main projection of CBCT. Effective and absorbed organ doses of CBCT at scout and main projection were calculated using PCXMC and PCXMCRotation software respectively. Effective dose and absorbed organ doses were compared with those obtained by TLDs and a 10-year-old child anthropomorphic phantom at the same exposure settings. Results: The effective dose of CBCT calculated by PCXMC software was 292.6 μSv, and that measured using TLD and anthropomorphic phantom was 292.5 μSv. The absorbed doses at the organs largely contributing to effective dose showed the small differences between two methods within the range from -18% to 20%. Conclusion: PCXMC software might be used as an alternative to the TLD measurement method for the effective and absorbed organ dose estimation in CBCT of large FOV in pediatric patients.

• 대한방사선기술학회지:방사선기술과학
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• 제32권3호
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• pp.307-312
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• 2009

CT 검사에서 수정체 차폐용 비스무트(bismuth)를 사용하여 수정체 선량의 감소효과를 유리선량계로 측정하여 비스무트 차폐효과 및 영상을 평가하였다. 안구 및 두부 CT 검사에서 차폐용 비스무트를 사용하여 수정체 선량의 감소와 차폐 효과를 평가하기 위해 인체모형 팬텀으로 유리선량계를 이용하여 수정체 선량을 평가하였다. 유리선량계를 이용하여 비스무트를 사용하기 전의 평균 선량은 21.54 mGy이었고, 사용 후의 선량은 10.46 mGy로 51.3%의 선량 감소효과가 있다. 차폐용 비스무트를 사용한 안구 64 MDCT 촬영에서 선량감소 효과가 있어 수정체를 포함한 안구 CT 스캔에서는 비스무트를 사용하여 검사하도록 권고한다.

• 대한디지털의료영상학회논문지
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• 제12권2호
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• pp.97-101
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• 2010

This experimental study is carried out one of the General Hospital in Kyungbok providence. Abdomen Phantom being located Anterior-posterior(AP) position on portable bed, and the portable X-ray generating device was placed the phantom at $-90^{\circ}$ direction. The experiment were set 65 kVp, 10 mAs, $10{\times}10\;cm^2$, 100 cm(FOD) for the measurement. Digital proportional counting tube survey meter was used for measuring the space scatter dose. Measurement points of horizontal distribution was set up at $30^{\circ}$ interval by increasing 50 cm radius of upside, downside, left and right. Vertical distribution of measurement points were set up for the vertical plane with a radius of at $30^{\circ}$ intervals with 50cm increments. It is concluded that longer distance from the soure of X-ray significantly decrease radiation dose to the patient and use of the radiation protection device should be applied in clinical practice to reduce dose to the patient.