• Journal of the Korean Society of Radiology
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• v.17 no.7
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• pp.1139-1147
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• 2023

The purpose of this paper is to present and evaluate the performance of a method for controlling the dose for optimal image acquisition while minimizing patient exposure by applying a small-sized Photomultiplier(SiPM) sensor inside a portable detector. Portable detectors have the advantage of being able to quickly access the patient's location for rapid diagnosis, but this mobility comes with the challenge of dose control. This paper presents a method to identify the dose that can have the DQE and optimal image quality of the detector through image evaluation based on IEC62220-1-1, an international standard for X-ray imaging devices, and to identify the optimal dose by matching the ADU of the image and the output of the SiPM Sensor. The Skull AP image was acquired by implementing the detector manufacturer's reference dose. The optimal dose was 342.8 µGy, and the optimal controlled dose was 148.3 µGy, which is 57 % of the manufacturer's reference dose. The Chest AP image was 81.9 µGy and the optimal controlled dose was 27.9 µGy, which is a high dose reduction effect of 66 %. In addition, the two images were analyzed by five radiologists and found to have no clinically significant difference in anatomical delineation.

• International Journal of Control, Automation, and Systems
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• v.1 no.3
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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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• 2003.10a
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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.

• Journal of the Ergonomics Society of Korea
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• v.24 no.2
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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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• v.11 no.2
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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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• v.45 no.4
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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.

• Progress in Medical Physics
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• v.1 no.1
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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.

• Journal of the Korean Society of Industry Convergence
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• v.15 no.3
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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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• v.30 no.1
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• pp.17-25
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• 2005

Since the safety of nuclear power plant has been becoming a big social issue the exposure dose of radiation for workers has been one of the important factors concerning the safety problem. The existing calculation methods of radiation dose used in the planning of radiation work assume that dose rate does not depend on the location within a work space thus the variation of exposure dose by different work path is not considered. In this study, a modified numerical method was presented to estimate the exposure dose during radiation work in radwaste storage considering the effects of the distance between a worker and sources. And a new numerical algorithm was suggested to search the optimal work path minimizing the exposure dose in pre-defined work space with given radiation sources. Finally, a virtual work simulation program was developed to visualize the exposure dose of radiation doting radiation works in radwaste storage and provide the capability of simulation for work planning. As a numerical example, a test radiation work was simulated under given space and two radiation sources, and the suggested optimal work path was compared with three predefined work paths. The optimal work path obtained in the study could reduce the exposure dose for the given test work. Based on the results, tile developed numerical method and simulation program could be useful tools in the planning of radiation work.

• Journal of The Korean Dental Society of Anesthesiology
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• v.14 no.3
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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.