• 한국의학물리학회지:의학물리
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• 제6권2호
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• pp.35-40
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• 1995

목적 : 필름배지를 이용하여 개인 피폭 선량을 측정하는 방법을 개발하고 그 특성을 알아보고자 한다. 재료 및 방법 : 필름으로는 Agfagaevart Personal monitoring 2/10 을 사용하였고, 필터로는 구리 0.3mm, 플라스틱 1.5mm, 알루미늄 0.6mm, 주석 0.8mm를 사용하였으며, 필름은 표준기관에서 교정하였다. 사용에너지는 ANSI N13.11 Category III, IV였고, 현상기는 수동현상기를, 농도계는 Xrite 농도계를 사용하였다. H＆D 곡선을 선량에 따라 구한 뒤 다항식 전개를 이용하여 선량에 대해 직선성을 갖도록 변환하였다. 이후 필터와 방사선 에너지 관계를 구하여 선량 및 에너지를 추정할 수 있는 알고리즘을 개발하였다. 결과 : 본 연구에서 개발된 선량 평가 알고리즘은 해당 Category 의 전에너지에 대해 30% 이내의 정확도를 만족시켜 이 알고리즘이 개인 피폭 선량 측정에 이용될 수 있음을 알았다. Category I, II , V에 대하여 보완한다면 완벽한 선량 평가 알고리즘이 될 것으로 기대된다.

• 한국의학물리학회지:의학물리
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• 제33권4호
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• pp.72-79
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• 2022

Purpose: The proficiency test was conducted to assess the performance of the dosimetry audit service provider in the readout practice of the dose delivered to patients in medical institutions. Methods: A certain amount of the absorbed dose to water for the high-energy X-ray from the medical linear accelerator (LINAC) installed in the Korea Research Institute of Standards and Science (KRISS) was delivered to the postal dose audit package given by the dosimetry audit service provider, in which the radio-photoluminescence (RPL) glass dosimeters were mounted. The dosimetry audit service provider read the RPL glass dosimeters and sent the readout dose value with its uncertainty to KRISS. The performance of the dosimetry audit service provider was evaluated based on the E_n number given in ISO/IEC 17043:2010. Results: The evaluated E_n number was -0.954. Based on the ISO/IEC 17043, the performance of the dosimetry service provider is "satisfactory." Conclusions: As part of the conformity assessment, the KRISS performed the proficiency test over the postal dose audit practice run by the dosimetry audit service provider. The proficiency test is in line with confirming the traceability of the medical institutions to the primary standard of absorbed dose to the water of the KRISS and ensuring the confidence of the dosimetry audit service provider.

• Nuclear Engineering and Technology
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• 제43권4호
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• pp.399-404
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• 2011

A LEGO-type multi-purpose dosimetry phantom was developed for intensity-modulated radiation therapy (IMRT), which requires various types of challenging dosimetry. Polystyrene, polyethylene, polytetrafluoroethylene (PTFE), and polyurethane foam (PU-F) were selected to represent muscle, fat, bone, and lung tissue, respectively, after considering the relevant mass densities, elemental compositions, effective atomic numbers, and photon interaction coefficients. The phantom, which is composed of numerous small pieces that are similar to LEGO blocks, provides dose and dose distribution measurements in homogeneous and heterogeneous media. The phantom includes dosimeter holders for several types of dosimeters that are frequently used in IMRT dosimetry. An ion chamber and a diode detector were used to test dosimetry in heterogeneous media under radiation fields of various sizes. The data that were measured using these dosimeters were in disagreement when the field sizes were smaller than $1.5{\times}1.5\;cm^2$ for polystyrene and PTFE, or smaller than $3{\times}3\;cm^2$ for an air cavity. The discrepancy was as large as 41% for the air cavity when the field size was $0.7{\times}0.7\;cm^2$, highlighting one of the challenges of IMRT small field dosimetry. The LEGO-type phantom is also very useful for two-dimensional dosimetry analysis, which elucidates the electronic dis-equilibrium phenomena on or near the heterogeneity boundaries.

• Journal of Magnetics
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• 제17권4호
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• pp.271-274
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• 2012

We examine dosimetry application of irradiated D-fructose materials using electron paramagnetic resonance (EPR). Consequently, we consider that fructose is one of best dosimetry materials. We found that fructose is one of best candidates for dosimetry due to high linearity tilt of EPR signal intensity as a function of dose, irrelevant to photon energy, constant fading value. Also, our results show that fructose materials can be applied as a radiation detector to very weak radiation doses of 0.001 Gray by using EPR at a low temperature (T = 220 K).

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.17-18
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• 2002

Last year, a three-year research program was started in order to establish an external audit system to radiotherapy QA in Japan. It consists of questionnaire surveys, mailed (off-site) dosimetry and visited (on-site) dosimetry at radiotherapy facilities in Japan. The first questionnaire was sent to all Japanese radiotherapy facilities in October 2001, surveying basic QA procedures at each facility. 628 answers were returned with the return rate of 87%. In February 2002, the second questionnaire was sent. Off-site and on-site dosimetry have been tested in several facilities, and will be started soon. We anticipates that this program will gradually grow to a radiotherapy quality control center similar to Radiological Physics Center at MD Anderson Hospital.

• Nuclear Medicine and Molecular Imaging
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• 제40권2호
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• pp.120-126
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• 2006

Radionuclide therapy has been continued for treatment of incurable diseases for past decades. Relevant evaluation of absorbed dose in radionuclide therapy is important to predict treatment output and essential for making treatment planning to prevent unexpected radiation toxicity. Many scientists in the field related with nuclear medicine have made effort to evolve concept and technique for internal radiation dosimetry in this review, basic concept of internal radiation dosimetry is described and recent progress in method for dosimetry is introduced.

• Journal of Radiation Protection and Research
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• 제49권1호
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• pp.1-18
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• 2024

Exponential growth has been observed in nuclear medicine procedures worldwide in the past decades. The considerable increase is attributed to the advance of positron emission tomography and single photon emission computed tomography, as well as the introduction of new radiopharmaceuticals. Although nuclear medicine procedures provide undisputable diagnostic and therapeutic benefits to patients, the substantial increase in radiation exposure to nuclear medicine patients raises concerns about potential adverse health effects and calls for the urgent need to monitor exposure levels. In the current article, model-based internal dosimetry methods were reviewed, focusing on Medical Internal Radiation Dose (MIRD) formalism, biokinetic data, human anatomy models (stylized, voxel, and hybrid computational human phantoms), and energy spectrum data of radionuclides. Key results from many articles on nuclear medicine dosimetry and comparisons of dosimetry quantities based on different types of human anatomy models were summarized. Key characteristics of seven model-based dose calculation tools were tabulated and discussed, including dose quantities, computational human phantoms used for dose calculations, decay data for radionuclides, biokinetic data, and user interface. Lastly, future research needs in nuclear medicine dosimetry were discussed. Model-based internal dosimetry methods were reviewed focusing on MIRD formalism, biokinetic data, human anatomy models, and energy spectrum data of radionuclides. Future research should focus on updating biokinetic data, revising energy transfer quantities for alimentary and gastrointestinal tracts, accounting for body size in nuclear medicine dosimetry, and recalculating dose coefficients based on the latest biokinetic and energy transfer data.

• 대한방사선치료학회지
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• 제27권2호
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• pp.167-174
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• 2015

목 적 : 복잡하고 정교하게 계획된 용적변조회전 방사선치료(Volumetric Arc Therapy, VMAT)의 Portal Dosimetry를 이용한 치료 전 선량평가가 다양한 인자에 따라 재현성을 유지하는지 분석하고자 하였다. 대상 및 방법 : 실험에는 TrueBeam STx$^{TM}$(Ver.1.5, Varian, USA), Portal dosimetry application(Ver.10, Varian)과 Portal Vision aS1000 Imager(Varian, USA)을 사용하였다. 두경부암 환자 2명, 전립샘암 환자 3명, 폐암 환자 1명, 자궁경부암 환자 1명, 총 7명의 환자에 대하여 Portal Dosimetry용 VMAT 전산화치료계획(Eclipse, Ver.10.0, Varian, USA)을 수립하였다. 오전 치료 전과 후 오후 치료 종료 후 각 4시간 간격을 두고 3회씩 5일에 걸쳐 선량평가를 시행하였다. Gamma pass rate(GPR 3%, 3mm 95%신뢰구간)와 Beam 출력의 상관관계를 확인하기 위하여 선량평가 시행 전 Beam 출력 을 물등가모형과 이온전리함(IBA dosimetry, Germany)을 이용하여 측정하였다. Electronic Portal Imaging Device(EPID) 상태에 따른 GPR 의 변화를 확인하기 위하여 EPID의 영상 교정 (Dark field correction, Flood field correction) 전과 후로 나누어 선량평가를 시행하였다. 또한 다엽콜리메이터(Multi Leaf Collimator) 상태에 따른 GPR의 변화를 확인하기 위해 다엽콜리메이터 Initialize 전과 후로 나누어 선량평가를 시행하였다. 결 과 : Portal Dosimetry를 시행하여 얻은 모든 환자들의 각 시간대 별 GPR의 평균값은 97.11%, 96.09%, 95.37% 였고 최대 차이를 보인 환자의 경우 각 시간대 별 GPR의 평균값은 95.73%, 94.20% 93.23% 였다. 선량평가 시점의 Beam 출력을 측정한 결과 각 시간대별 평균값은 100.45%, 100.46%, 100.59% 였다. EPID의 영상 교정(Dark field correction, Flood field correction)을 시행하기 전과 후의 대상 환자들의 GPR의 평균값은 95.94 %, 96.01% 였다. 또한 다엽콜리메이터 의 Initialize 를 시행하기 전과 후의 대상 환자들의 GPR 의 평균값은 95.83%, 96.40%였다. 결 론 : 치료기 사용시간이 경과됨에 따라 대상 환자들의 GPR 평균값이 0.8% 감소함을 확인할 수 있었다. Beam 출력은 각 측정시점에 0.1% 오차범위 안에서 일정한 상태를 유지하였다. EPID의 영상 교정 전, 후 의 선량평가 결과 GPR은 평균 0.1% 차이를 나타내었다. 다엽콜리메이터의 Initialize 전, 후의 선량평과 결과 Initialize 시행 후 GPR이 평균 0.6% 상승하였고 다엽콜리메이터 상태에 따라 GPR이 변화할 수 있다는 것을 확인할 수 있었다. 복잡하고 정교하게 계획된 VMAT의 치료 전 선량평가 도구로서 재현성을 유지하며 Portal Dosimetry를 이용하기 위해서는 주기적인 장비의 점검뿐만 아니라, 선량평가에 영향을 미칠 수 있는 다양한 인자들에 대한 관리가 이뤄져야 할 것으로 판단된다.

• 한국의학물리학회지:의학물리
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• 제28권2호
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• pp.61-66
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• 2017

The aim of this study is to investigate the characteristics of portal dosimetry in comparison with the MapCHECK2 measurments. In this study, a total of 65 treatment plans including both volumetric modulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT) were retrospectively selected and analyzed (45 VMAT plans and 20 IMRT plans). A total of 4 types of linac models (VitalBeam, Trilogy, Clinac 21EXS, and Clianc iX) were used for the comparison between portal dosimetry and the MapCHECK2 measurements. The VMAT plans were delivered with two VitalBeam linacs (VitalBeam1 and VitalBeam2) and one Trilogy while the IMRT plans were delivered with one Clinac 21EXS and one Clinacl iX. The global gamma passing rates of portal dosimetry and the MapCHECK2 measurements were analyzed with a gamma criterion of 3%/3 mm for IMRT while those were analyzed with a gamma criterion of 2%/2 mm for VMAT. Spearman's correlation coefficients (r) were calculated between the gamma passing rates of portal dosimetry and those of the MapCHECK2 measurements. For VMAT, the gamma passing rates of portal dosimetry with the VitalBeam1, VitalBeam2, and Trilogy were $97.3%{\pm}3.5%$, $97.1%{\pm}3.4%$, and $97.5%{\pm}1.9%$, respectively. Those of the MapCHECK2 measurements were $96.8%{\pm}2.5%$, $96.3%{\pm}2.7%$, and $97.4%{\pm}1.3%$, respectively. For IMRT, the gamma passing rates of portal dosimetry with Clinac 21EXS and Clinac iX were $99.7%{\pm}0.3%$ and $99.8%{\pm}0.2%$, respectively. Those of the MapCHECK2 measurements were $96.5%{\pm}3.3%$ and $97.7%{\pm}3.2%$, respectively. Except for the result with the Trilogy, no correlations were observed between the gamma passing rates of portal dosimetry and those of the MapCHECK2 measurements. Therefore, both the MapCHECK2 measurements and portal dosimetry can be used as an alternative to each other for patient-specific QA for both IMRT and VMAT.

• Nuclear Engineering and Technology
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• 제54권7호
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• pp.2599-2605
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• 2022

The Korea Retrospective Dosimetry network (KREDOS) performed an inter-laboratory comparison to confirm the harmonization and reliability of the results of retrospective dosimetry using mobile phone. The mobile phones were exposed to ¹⁹²Ir while attached to the human phantoms in the field experiment, and the exposure doses read by each laboratory were compared. This paper describes the reference dosimetry performed to present the reference values for inter-comparison and to obtain additional information about the dose distribution. Reference dosimetry included both measurement using LiF:Mg,Cu,Si and calculation via MCNP simulation to allow a comparison of doses obtained with the two different methodologies. When irradiating the phones, LiF elements were attached to the phones and phantoms and irradiated at the same time. The comparison results for the front of the phantoms were in good agreement, with an average relative difference of about 10%, while an average of about 16% relative difference occurred for the back and side of the phantom. The differences were attributed to the different characteristics of the physical and simulated phantoms, such as anatomical structure and constituent materials. Nevertheless, there was about 4% of under-estimation compared to measurements in the overall linear fitting, indicating the calculations were well matched to the measurements.