• 응용통계연구
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• 제27권1호
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• pp.13-20
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• 2014

제 1상 임상시험의 목적은 피험자가 견딜 수 있는 최대의 용량인 최대허용용량(Maimum Tolerated Dose; MTD)을 추정하는 것이다. 최대허용용량을 추정하는 방법으로는 SM방법, ATD방법, CRM방법 등이 있다. 본 연구에서는 제 1상 임상시험에서 멈춤규칙을 이용한 최대허용용량 추정법을 제안하였다. 제안한 최대허용용량 추정법은 연속재평가방법(Continual Reassessment Method; CRM)과 모의실험을 통해 비교하였다.

• Communications for Statistical Applications and Methods
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• 제19권1호
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• pp.57-64
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• 2012

제 1상 임상시험에서 주목표는 부작용이 발생하지 않고 피험자가 견딜 수 있는 한도 내에서 최대 용량인 최대허용용량(Maximum Tolerated Dose; MTD)을 결정하는 것이다. 최대허용용량을 결정하는 방법에는 SM방법, CRM방법 등이 있는데 본 논문에서는 기존의 Stopping rule을 변형한 두 단계 MTD 추정방법을 제안하였다. 기존의 방법들을 본 논문에서 제안한 방법과 모의실험을 통하여 비교하였다.

• 한국환경성돌연변이발암원학회지
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• 제19권1호
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• pp.39-45
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• 1999

Human Carcinogenic Potency (HCP) can be estimated based on human daily exposure dose to carcinogen (Dh), body weight (Wh), 10% tumorigenic dose (TD10), and slope factor at TD10 (Q10) from 2-yr bioassay data. This approach is more relevant to humans generally exposed to low doses of carcinogens and can reduce more of extrapolation errors from high dose in animal experiments to low dose in humans than HERP (human exposure dose/rodent potency dose) proposed by Ames et al. (Science, 236, 271-280, 1987). TD50 and HERP have been routinely used to compare rodent carcinogenic potency and human carcinogenic potency, but those approaches have had limitations in extrapolation of high dose to low dose in humans. The advantages of HCP are to estimate human exposure dose (Dh) by human monitoring instead of environmental monitoring, to consider slope factor (Q10) which reflects the tendency of curve at low dose, and to use TD10 which represents much lower dose thant TD50 or HERP. HCP will be a useful parameter for the estimation of human carcinogenic potency in risk assessment and management of carcinogens.

• Journal of Radiation Protection and Research
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• 제45권1호
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• pp.2-10
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• 2020

Background: Huge amounts of radionuclides were released into the environment due to the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, which caused not only serious contamination on the ground, but also radiation exposure to the public. One problem that remains in performing the dose estimation is the difficulty of estimating the internal thyroid dose due to the intake of radioiodine (mainly, ¹³¹I) because of limitations to the human data available. Materials and Methods: The relevant papers were collected and reviewed by the authors. The results of thyroid dose estimates from different studies were tabulated for comparison. Results and Discussion: The thyroid dose estimates from the studies varied widely. The dose estimates by the United Nations Scientific Committee on the Effects of Atomic Radiation were higher than the others due to the ingestion dose being based on conservative assumptions. The dose estimates by Japanese experts were mostly below 20-30 mSv. The recent studies suggested that exposure on March 12, 2011 would be crucial for late evacuees from the areas near the FD-NPP because of the possible intake of short-lived radionuclides other than ¹³¹I. Further multilateral studies are vital to reduce uncertainties in the present dose estimations. Conclusion: The estimation of the thyroid doses to Fukushima residents still has many uncertainties. However, it is considered unlikely that the thyroid doses exceeded 50 mSv except in some extreme cases. Further multilateral studies are thus necessary to reduce the uncertainties in the present dose estimations.

• Journal of Radiation Protection and Research
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• 제28권1호
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• pp.59-63
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• 2003

Purpose : Measurement of transmission dose is useful for in vivo dosimetry of QA purpose. The objective of this study is to develope an algorithm for estimation of tumor dose using measured transmission dose for open radiation field. Materials and Methods : Transmission dose was measured with various field size (FS), phantom thickness (Tp), and phantom chamber distance (PCD) with a acrylic phantom for 6 MV and 10 MV X-ray Source to chamber distance (SCD) was set to 150 cm. Measurement was conducted with a 0.6 cc Farmer type ion chamber. Using measured data and regression analysis, an algorithm was developed for estimation of expected reading of transmission dose. Accuracy of the algorithm was tested with flat solid phantom with various settings. Results : The algorithm consisted of quadratic function of log(A/P) (where A/P is area-perimeter ratio) and tertiary function of PCD. The algorithm could estimate dose with very high accuracy for open square field, with errors within ${\pm}0.5%$. For elongated radiation field, the errors were limited to ${\pm}1.0%$. Conclusion : The developed algorithm can accurately estimate the transmission dose in open radiation fields with various treatment settings.

• 방사성폐기물학회지
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• 제19권2호
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• pp.243-253
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• 2021

In the dismantling process of a reactor coolant system (RCS) piping, a radiation protection plan should be established to minimize the radiation exposure doses of dismantling workers. Hence, it is necessary to estimate the individual effective dose in the RCS piping dismantling process when decommissioning a nuclear power plant. In this study, the radiation exposure doses of the dismantling workers at different positions was estimated using the MicroShield dose assessment program based on the NUREG/CR-1595 report. The individual effective dose, which is the sum of the effective dose to each tissue considering the working time, was used to estimate the radiation exposure dose. The estimations of the simulation results for all RCS piping dismantling tasks satisfied the dose limits prescribed by the ICRP-60 report. In dismantling the RCS piping of the Kori-1 or Wolsong-1 units in South Korea, the estimation and reduction method for the radiation exposure dose, and the simulated results of this study can be used to implement the radiation safety for optimal dismantling by providing information on the radiation exposure doses of the dismantling workers.

• Journal of Radiation Protection and Research
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• 제41권3호
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• pp.291-300
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• 2016

Background: It is necessary to assess radiation dose to workers due to inhalation of airborne particulates containing naturally occurring radioactive materials (NORM) to ensure radiological safety required by the Natural Radiation Safety Management Act. The objective of this study is to develop an internal dose assessment procedure for workers at industries using raw materials containing natural radionuclides. Materials and Methods: The dose assessment procedure was developed based on harmonization, accuracy, and proportionality. The procedure includes determination of dose assessment necessity, preliminary dose estimation, airborne particulate sampling and characterization, and detailed assessment of radiation dose. Results and Discussion: The developed dose assessment procedure is as follows. Radioactivity concentration criteria to determine dose assessment necessity are $10Bq{\cdot}g^{-1}$ for $^{40}K$ and $1Bq{\cdot}g^{-1}$ for the other natural radionuclides. The preliminary dose estimation is performed using annual limit on intake (ALI). The estimated doses are classified into 3 groups ( < 0.1 mSv, 0.1-0.3 mSv, and > 0.3 mSv). Air sampling methods are determined based on the dose estimates. Detailed dose assessment is performed using air sampling and particulate characterization. The final dose results are classified into 4 different levels ( < 0.1 mSv, 0.1-0.3 mSv, 0.3-1 mSv, and > 1 mSv). Proper radiation protection measures are suggested according to the dose level. The developed dose assessment procedure was applied for NORM industries in Korea, including coal combustion, phosphate processing, and monazite handing facilities. Conclusion: The developed procedure provides consistent dose assessment results and contributes to the establishment of optimization of radiological protection in NORM industries.

• Current Optics and Photonics
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• 제1권5호
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• pp.551-555
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• 2017

Tissue optics is a well-established and extensively studied area. In the last decades, Monte Carlo simulation (MCS) has been one of the standard tools for simulation of light propagation in turbid media. The utilization of parallel processing exhibits dramatic increase in the speed of MCS's of photon migration. Some calculations based on MCS can be completed within a few seconds. Since the MCS's have the potential to become a real time calculation method, a dynamic accuracy estimation, which is also known as history by history statistical estimators, is required in the simulation code to automatically terminate the MCS as the results' accuracy achieves a high enough level. In this work, spatial and time-domain GPU-based MCS, adopting the dynamic accuracy estimation, are performed to calculate the light dose/reflectance in homogeneous and heterogeneous tissue media. This dynamic accuracy estimation can effectively derive the statistical error of optical dose/reflectance during the parallel Monte Carlo process.

• 센서학회지
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• 제25권6호
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• pp.394-398
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• 2016

In this paper, a fire detection system based on quantitative risk estimation is presented. Multiple sensors are used to build a comprehensive indicator that represents the risk of fire quantitatively. The proposed fire risk estimation method consists of two stages which determines the occurrence of fire and estimates the toxicity of the surveillance area. In the first stage, fire is reliably detected under diverse fire scenarios. The risk of fire is estimated in the second stage. Applying Purser's Fractional Effective Dose (FED) model which quantitates harmfulness of toxic gases, the risk of the surveillance area and evacuation time are calculated. A fire experiment conducted using four different types of combustion materials for the verification of the system resulted in a maximum error rate of 12.5%. By using FED calculation and risk estimation methods, the proposed system can detect various signs of fire faster than conventional systems.

• 한국의학물리학회지:의학물리
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• 제27권4호
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• pp.232-235
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• 2016

The purpose of this study is to develop the treatment planning system (TPS) based on Monte-Carlo simulation for BNCT. In this paper, we will propose a method for dose estimation by Monte-Carlo simulation using the CT image, and will evaluate the accuracy of dose estimation of this TPS. The complicated geometry like a human body allows defining using the lattice function in MCNPX. The results of simulation such as flux or energy deposition averaged over a cell, can be obtained using the features of the tally provided by MCNPX. To assess the dose distribution and therapeutic effect, dose distribution was displayed on the CT image, and dose volume histogram (DVH) was employed in our developed system. The therapeutic effect can be efficiently evaluated by these evaluation tool. Our developed TPS could be effectively performed creating the voxel model from CT image, the estimation of each dose component, and evaluation of the BNCT plan.