• 한국방사선학회논문지
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• 제17권7호
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• pp.1139-1147
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• 2023

본 논문에서는 소형 크기인 SiPM Sensor를 휴대용 검출기 내부에 적용하여 환자 피폭을 최소화하면서도 최적의 이미지 획득을 위한 선량을 제어하기 위한 방법을 제시하고 이에 대한 성능을 평가하는 것을 목적으로 한다. 휴대용 검출기는 환자의 위치에 빠르게 접근하여 신속한 진단을 가능하게 하는 장점이 있지만 이러한 이동성은 선량 관리의 어려움을 동반한다. X-ray imaging devices 국제 표준인 IEC62220-1-1 기준의 이미지 평가를 통해 검출기의 DQE와 최적 화질을 갖을 수 있는 선량을 확인하고 영상의 ADU와 SiPM Sensor의 출력을 매칭 하여 최적 선량을 확인하는 방법을 제시하였다. 검출기 제조사 기준 선량과 최적 선량 구현으로 획득된 Skull AP 이미지는 제조사 기준 342.8 µGy, 최적 제어 선량은 148.3 µGy로 조사되어 제조사 기준 선량 대비 57 %, Chest AP는 제조사 기준 81.9 µGy, 제어된 최적 선량은 27.9 µGy로 66 %의 높은 선량 감소 효과가 확인되었다. 또한 촬영된 두 영상은 방사선사 5명의 분석을 통해 해부학적 구조물을 판별하기에 임상적으로 유의미한 차이가 없는 것으로 확인되었다.

• International Journal of Control, Automation, and Systems
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• 제1권3호
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• pp.282-288
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• 2003

It is known that HIV (Human Immunodeficiency Virus) infection, which causes AIDS after some latent period, is a dynamic process that can be modeled mathematically. Effects of available anti-viral drugs, which prevent HIV from infecting healthy cells, can also be included in the model. In this paper we illustrate control theory can be applied to a model of HIV infection. In particular, the drug dose is regarded as control input and the goal is to excite an immune response so that the symptom of infected patient should not be developed into AIDS. Finite horizon optimal control is employed to obtain the optimal schedule of drug dose since the model is highly nonlinear and we want maximum performance for enhancing the immune response. From the simulation studies, we found that gradual reduction of drug dose is important for the optimality. We also demonstrate the obtained open-loop optimal control is vulnerable to parameter variation of the model and measurement noise. To overcome this difficulty, we finally present nonlinear receding horizon control to incorporate feedback in the drug treatment.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1951-1956
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• 2003

It is known that HIV (Human Immunodeficiency Virus) infection, which causes AIDS after some latent period, is a dynamic process that can be modeled mathematically. Effects of available anti-viral drugs, which prevent HIV from infecting healthy cells, can also be included in the model. In this paper we illustrate control theory can be applied to a model of HIV infection. In particular, the drug dose is regarded as control input and the goal is to excite an immune response so that the symptom of infected patient should not be developed into AIDS. Finite horizon optimal control is employed to obtain the optimal schedule of drug dose since the model is highly nonlinear and we want maximum performance for enhancing the immune response. From the simulation studies, we find that gradual reduction of drug dose is important for the optimality. We also demonstrate the obtained open-loop optimal control is vulnerable to parameter variation of the model and measurement noise. To overcome this difficulty, we finally present nonlinear receding horizon control to incorporate feedback in the drug treatment.

• 대한인간공학회지
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• 제24권2호
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• pp.71-77
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• 2005

In spite of the importance of nuclear power as one of major electric energies in Korea, the nuclear safety has become the most serious social issue in the operation of the nuclear power plant. In this paper, a virtual work simulation program was developed to predict exposure dose during radiation work in radwaste storage. The work simulation program was developed. using $Java ^{TM}$applet and VRML-virtual reality modeling language. A numerical algorithm to find the optimal work path which minimize exposure dose during the given work, was developed and exposure dose on the optimal work path was compared with that on the shortest path. Comparing with the shortest path for the given work, the predicted optimal path consumed longer work time by II% but reduced total exposure dose by 46%. The simulation result showed that the exposure dose depended on not only work time, but also the distance between the worker and the radiation source. The developed simulation program could be a useful tool for the planning of radioactive waste work to increase the radiation safety of workers.

• International journal of thyroidology
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• 제11권2호
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• pp.137-142
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• 2018

Background and Objectives: Radioactive iodine therapy (RAI) is an important treatment modality of Graves' disease (GD), but there is still not a consensus on the optimal dosage regimen. We studied the treatment success rate of different RAI doses, and examined which clinical markers were useful for determining the optimal RAI dosage for successful therapy in Korean patients. Materials and Methods: We retrospectively studied 123 patients with GD treated with RAI between 2004 and 2014 at Chonnam National University Hwasun Hospital. The responder group was defined as patients who developed hypothyroidism requiring levothyroxine replacement following RAI, regardless of the RAI dosage. Results: A total of 54 patients (43.9%) became hypothyroid after the first dose, and 31 needed two to four additional doses to achieve hypothyroidism. In the responder group as a whole (85 patients), the mean total dose of RAI was $15.5{\pm}7.0mCi$ and the mean thyroid volume (TV) was $35.4{\pm}23.4mL$. When divided into low dose (<15 mCi, n=46) and high dose (${\geq}15mCi$, n=39) responder groups, TV was significantly lower in the low-dose responder group ($25.7{\pm}11.4$ vs. $48.4{\pm}31.3$, p<0.001). The optimal cut-off TV for the low-dose responder group was <32.37 mL (sensitivity 80.9%, specificity 76.7%). Conclusion: TV had significant effects on the outcome of RAI in GD patients. The optimal fixed RAI dose for Korean GD patients with a large goiter (${\geq}33mL$) should be at least 15 mCi to achieve the best outcome.

• Clinical and Experimental Reproductive Medicine
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• 제45권4호
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• pp.183-188
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• 2018

Objective: The purpose of this retrospective study was to evaluate the appropriateness of various follicle-stimulating hormone (FSH) starting doses in expected normal responders based on the nomogram developed by La Marca et al. Methods: A total of 117 first in vitro fertilization cycles performed from 2011 to 2017 were selected. All women were expected normal responders and used a recombinant FSH and flexible gonadotropin-releasing hormone antagonist protocol. The FSH starting dose was empirically determined (150, 225, or 300 IU). The FSH starting dose indicated by La Marca's nomogram was determined using female age and serum $anti-M{\ddot{u}}llerian$ hormone or basal FSH levels. If the administered dose was exactly the same as the proposed dose, the cycle was assigned to the concordant group (34 cycles). If not, it was assigned to the discordant group (83 cycles). Optimal ovarian response was defined as a total of 8-14 oocytes, hypo-response as < 8 oocytes, and hyper-response as > 14 oocytes. Results: Between the concordant and discordant group, ovarian response (optimal, 32.4% vs. 27.7%; hypo-response, 55.9% vs. 54.2%; and hyper-response, 11.8% vs. 18.1%) and the number of total or mature oocytes were similar. Ovarian hyperstimulation syndrome was rare in both groups (0% vs. 1.2%). The implantation rate, clinical pregnancy rate, miscarriage rate, and live birth rate were all similar. Conclusion: The use of the proposed FSH starting dose determined using La Marca's nomogram did not enhance the optimal ovarian response rate or pregnancy rate in expected normal responders. Individualization of the FSH starting dose by La Marca's nomogram appears to have no distinct advantages over empiric choice of the dose in expected normal responders.

• 한국의학물리학회지:의학물리
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• 제1권1호
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• pp.23-29
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• 1990

In order to explane the stereotactic procedure, the three steps of the procedure (target localization, dose planning, and radiation treatment) must be examined separately. The ultimate accuracy of the full procedure is dependent on each of these steps and on the consistancy of the approach The concern in this article was about dose planning, which is a important factor to the success of radiation treatment. The major factor in dose planning is a dosimetry system to evaluate the dose delivered to the target and normal tissues in the patient, while it generates an optimal dose distribution that will satisfy a set of clinical criteria for the patient. A three-dimensional treatment planning program is a prerequisite for treatment plan optimization. It must cover 3-D methods for representing the patient, the dose distributions, and beam settings. The major problems and possible modelings about 3-D factors and optimization technique were discussed to simplify and solve the problems associatied with 3-D optimization, with relative ease and efficiency. These modification can simplify the optimization problem while saving time, and can be used to develop reference dose planning system to prepare standard guideline for the selection of optimum beam parameters, such as the target position, collimator size, arc spacing, the variation in arc length and weight. The method yields good results which can then be simulated and tailored to the individual case. The procedure needed for dose planning in stereotactic radiosurgery is shown in figure 1.

• 한국산업융합학회 논문집
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• 제15권3호
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• pp.71-77
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• 2012

This study gives the optimal reaction conditions, reaction mechanisms, reaction rates leaded from the oxidation of phenol by electron beam accelerator and ozone used for recent water treatment. It gives the new possibility of water treatment process to effectively manage industrial sewage containing toxic organic compounds and biological refractory materials. The high decomposition of phenol was observed at the low dose rate, but at this low dose rate, the reaction time was lengthened. So we must find out the optimal dose rate to promote high oxidation of reactants. The reason why the TOC value of aqueous solution wasn't decreased at the low dose was that there were a lot of low molecular organic acids as an intermediates such as formic acid or glyoxalic acid. In order to use both electron beam accelerator and biological treatment for high concentration refractory organic compounds, biological treatment is needed when low molecular organic compounds exist abundantly in sewage. In this experiment, the condition of making a lot of organic acids is from 5 kGy into 20 kGy dose. Decomposition rate of phenol by electron beam accelerator was first order reaction up to 300ppm phenol solution on the basic of TOC value and also showed first order reaction by using both air and ozone as an oxidants.

• Journal of Radiation Protection and Research
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• 제30권1호
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• pp.17-25
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• 2005

원자력 발전의 안정성이 사회적 문제로 제기된 이후 작업종사자에 대한 작업 중 방사선 피폭량에 대한 관심이 높아지고 있다. 현재의 방법에 의하면 방사선 작업 계획의 수립 시 작업 공간 내 선량률이 일정하다는 가정 하에 피폭선량을 예측하므로 작업 경로에 따른 피폭선량의 변화에 대한 고려가 이루어지지 않고 있다. 본 연구에서는 작업자와 선원과의 거리가 고려되 수정된 방사선 피폭량 계산식을 이용하여 방사성 폐기물 저장시설에서의 작업 중 작업경로 변화에 따른 방사선 피폭량을 계산하였다. 이 계산식을 이용하여 주어진 작업 공간과 선원 조건하에서 작업 중 방사선 피폭량을 최소로 하는 최적 작업경로를 탐색할 수 있는 수치해석 알고리즘을 제안하였다. 이를 위하여 2차원 작업공간에서 무한개의 작업경로를 유한개의 경로로 근사화하고 근사화된 모든 작업경로 중 피폭선량이 최소가 되는 작업경로를 탐색하였다. 또한, 3차원 그래픽 기술과 Java 프로그래밍을 이용한 가상작업 시뮬레이션 프로그램을 개발하고 작업 공간의 선량률 가시화 및 가상 작업 시뮬레이션을 수행하여 방사선 작업 계획의 수립을 위한 도구로서의 가능성을 검토하였다. 수치해석 계산과 시뮬레이션 과정을 통하여 최적 작업경로는 작업자와 선원과의 거리를 증가시키고 작업 시간을 단축시킬 수 있는 경로로 제시되었고, 이를 바탕으로 방사선 피폭량은 작업시간뿐만 아니라 작업자와 선원간의 거리에 영향을 받음과 최적화된 방사선 방호를 위해 작업경로가 고려되어야 함을 확인하였다.

• 대한치과마취과학회지
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• 제14권3호
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• pp.151-155
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• 2014

Background: Dexmedetomidine is known to be administered for sedation safely even in a very elderly patient. The purpose of this study was to determine the effect of age on clinically optimal dose of dexmedetomidine for sedation. Methods: We enrolled 50 patients ASA class I and II, scheduled for lower extremity surgery that need. They were classified into a young group (n = 26), aged below 75 and an old group (n = 24), aged above 75. Dexmedetomidine was continuously infused $0.5{\mu}g/kg$ within 10 min, followed by maintenance at a dose of $0.5{\mu}g/kg/min$, initially. The next dose was selected using the Dixon's up-and-down method. Results: The cED50 of dexmedetomidine required to maintain optimal sedation level in young and old group were 0.50 and $0.48{\mu}g/kg$, respectively. With isotonic regression, cED95 of dexmedetomidine was $0.71{\mu}g/kg$ (95% confidence intervals $0.57-1.06{\mu}g/kg$) and $0.58{\mu}g/kg$ (95% confidence intervals $0.51-0.67{\mu}g/kg$). There were no significant differences in cED50 (P = 0.21), recovery variables, or incidence of side effects between the two groups. Conclusions: Clinically optimal dose of dexmedetomidine was not affected to the age during sedation.