• Progress in Medical Physics
• /
• v.20 no.4
• /
• pp.269-276
• /
• 2009

Radiation treatment techniques using photon beam such as three-dimensional conformal radiation therapy (3D-CRT) as well as intensity modulated radiotherapy treatment (IMRT) demand accurate dose calculation in order to increase target coverage and spare healthy tissue. Both jaw collimator and multi-leaf collimators (MLCs) for photon beams have been used to achieve such goals. In the Pinnacle3 treatment planning system (TPS), which we are using in our clinics, a set of model parameters like jaw collimator transmission factor (JTF) and MLC transmission factor (MLCTF) are determined from the measured data because it is using a model-based photon dose algorithm. However, model parameters obtained by this auto-modeling process can be different from those by direct measurement, which can have a dosimetric effect on the dose distribution. In this paper we estimated JTF and MLCTF obtained by the auto-modeling process in the Pinnacle3 TPS. At first, we obtained JTF and MLCTF by direct measurement, which were the ratio of the output at the reference depth under the closed jaw collimator (MLCs for MLCTF) to that at the same depth with the field size $10{\times}10\;cm^2$ in the water phantom. And then JTF and MLCTF were also obtained by auto-modeling process. And we evaluated the dose difference through phantom and patient study in the 3D-CRT plan. For direct measurement, JTF was 0.001966 for 6 MV and 0.002971 for 10 MV, and MLCTF was 0.01657 for 6 MV and 0.01925 for 10 MV. On the other hand, for auto-modeling process, JTF was 0.001983 for 6 MV and 0.010431 for 10 MV, and MLCTF was 0.00188 for 6 MV and 0.00453 for 10 MV. JTF and MLCTF by direct measurement were very different from those by auto-modeling process and even more reasonable considering each beam quality of 6 MV and 10 MV. These different parameters affect the dose in the low-dose region. Since the wrong estimation of JTF and MLCTF can lead some dosimetric error, comparison of direct measurement and auto-modeling of JTF and MLCTF would be helpful during the beam commissioning.

• Radiation Oncology Journal
• /
• v.20 no.1
• /
• pp.81-90
• /
• 2002

Purpose : To establish and verify the proper and the practical IMRT (Intensity--modulated radiation therapy) patient QA (Quality Assurance). Materials and Methods : An IMRT QA which consists of 3 steps and 16 items were designed and examined the validity of the program by applying to 9 patients, 12 IMRT cases of various sites. The three step OA program consists of RTP related QA, treatment information flow QA, and a treatment delivery QA procedure. The evaluation of organ constraints, the validity of the point dose, and the dose distribution are major issues in the RTP related QA procedure. The leaf sequence file generation, the evaluation of the MLC control file, the comparison of the dry run film, and the IMRT field simulate image were included in the treatment information flow procedure QA. The patient setup QA, the verification of the IMRT treatment fields to the patients, and the examination of the data in the Record & Verify system make up the treatment delivery QA procedure. Results : The point dose measurement results of 10 cases showed good agreement with the RTP calculation within $3\%$. One case showed more than a $3\%$ difference and the other case showed more than $5\%$, which was out side the tolerance level. We could not find any differences of more than 2 mm between the RTP leaf sequence and the dry run film. Film dosimetry and the dose distribution from the phantom plan showed the same tendency, but quantitative analysis was not possible because of the film dosimetry nature. No error had been found from the MLC control file and one mis-registration case was found before treatment. Conclusion : This study shows the usefulness and the necessity of the IMRT patient QA program. The whole procedure of this program should be peformed, especially by institutions that have just started to accumulate experience. But, the program is too complex and time consuming. Therefore, we propose practical and essential QA items for institutions in which the IMRT is performed as a routine procedure.

• The Korean Journal of Nuclear Medicine
• /
• v.32 no.5
• /
• pp.414-424
• /
• 1998

Purpose: Cross-modality coregistration of positron emission tomography (PET) and magnetic resonance imaging (MR) could enhance the clinical information. In this study we propose a refined technique to improve the robustness of registration, and to implement more realistic visualization of the coregistered images. Materials and Methods: Using the sinogram of PET emission scan, we extracted the robust head boundary and used boundary-enhanced PET to coregister PET with MR. The pixels having 10% of maximum pixel value were considered as the boundary of sinogram. Boundary pixel values were exchanged with maximum value of sinogram. One hundred eighty boundary points were extracted at intervals of about 2 degree using simple threshold method from each slice of MR images. Best affined transformation between the two point sets was performed using least square fitting which should minimize the sum of Euclidean distance between the point sets. We reduced calculation time using pre-defined distance map. Finally we developed an automatic coregistration program using this boundary detection and surface matching technique. We designed a new weighted normalization technique to display the coregistered PET and MR images simultaneously. Results: Using our newly developed method, robust extraction of head boundary was possible and spatial registration was successfully performed. Mean displacement error was less than 2.0 mm. In visualization of coregistered images using weighted normalization method, structures shown in MR image could be realistically represented. Conclusion: Our refined technique could practically enhance the performance of automated three dimensional coregistration.

• The Korean Journal of Nuclear Medicine Technology
• /
• v.17 no.2
• /
• pp.44-47
• /
• 2013

Purpose: There are several methods of measuring SUV in PET/CT imaging including $SUV_{bw}$ which uses the body weight, $SUV_{bsa}$ which that uses body surface area and $SUV_{lbm}$ which uses lean body mass. Currently, Seoul National University Hospital uses $SUV_{bw}$ method which minimizes the variability. In this study, we compared and analyzed the correlation between $SUV_{bw}$ and $SUV_{bsa}$ according to patients' body mass index. Materials and Methods: Using Biograph mCT40 (Siemens, Germany), we conducted $^{18}F-FDG$ PET/CT imaging on 70 patients (41 males, 29 females; ages $58.04{\pm}12.44$). We classified the patients as underweight (BMI<20), normal weight (20$${\leq_-}$$BMI<25), overweight (25$${\leq_-}$$BMI<30), obese (30$${\leq_-}$$BMI<35) and severely obese (35$${\leq_-}$$BMI) according to the patient's sex, age and BIM. Then, bone, liver and lungs were set as ROI for calculation of maximum values of $SUV_{bw}$ and $SUV_{bsa}$, through Syngo.via VA11A analysis program. Results: Comparing the five groups divided according to the BMI by the standard differences between $SUV_{bw}$ to $SUV_{bsa}$, $SUV_{max}$ was measured to be $0.66{\pm}0.15$, $0.78{\pm}0.35$, $0.77{\pm}0.21$, $1.00{\pm}0.44$, $1.53{\pm}0.38$ for bones in underweight, normal weight, overweight, obese and severely obese groups, respectively. For liver, values of $SUV_{max}$ were $1.64{\pm}0.16$, $2.06{\pm}0.34$, $2.19{\pm}0.21$, $2.52{\pm}0.21$ and $2.74{\pm}0.40$ in the same order. And for lung, values of $SUV_{max}$ were $0.69{\pm}0.33$, $0.54{\pm}0.17$, $0.62{\pm}0.23$, $0.83{\pm0.29}$, $1.03{\pm}0.30$. Conclusion: By comparing and analyzing the differences between $SUV_{bw}$ and $SUV_{bsa}$ in this study, it was found that the differences between $SUV_{bw}$ and $SUV_{bsa}$ increased as patient's BMI increased. Thus, there is room for error in the values of SUV depending on the methods of calculations, and appropriate methods must be applied according to the circumstances in clinical settings.

• Economic and Environmental Geology
• /
• v.26 no.1
• /
• pp.21-27
• /
• 1993

Fluid inclusion has been widely used to study the origin and physiochemical conditions of ore deposits. However, it is difficult to get the accurate physiochemical data from fluid inclusion study due to the error of microthermometric data and the complexity of calculation of density and isochore of fluid inclusion. The computer programs HALWAT, $CO_2$, and CHNACL written by Nicholls and Crowford (1985) partly contributed to improve the accuracy of physiochemical data by using complicated equations. These programs are applied to determine the densities and isochores of fluid inclusions for the Cretaceous Keumhak mine using Choi and So's data (1992) and for the Jurassic Samhwanghak mine using Yun's data (1990). The estimated PoT for Keumhak mine from calculated isochores of coexisting fluid inclusions are $230^{\circ}{\sim}290^{\circ}C$ and 500~800 bar which matche well to the poT estimated by Choi and So ($280^{\circ}{\sim}360^{\circ}C$ and 500~800 bar, 1992). However, the poT for Samwhanghak mine estimated in this study by combining the calculated isochores and sulfur isotope geothermometer data by Yun (1990) are about 4~7 kb at $329{\pm}50^{\circ}{\sim}344{\pm}55^{\circ}C$ which are quite different form the P-T estimates by Yun ($255^{\circ}{\sim}294^{\circ}C$ and 1.2~1.9kb, 1990). This discrepancy caused by misinterpretation of homogenization temperature (Th) of fluid inclusion and by application of inappropriate isochores. The application of homogenization temperature and/or inappropriately selected isochore to determine the trapping PoT condition of ore-deposits should be avoided, particularly for ore-deposits formed at pressures higher than 1~2 kb.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.13 no.3
• /
• pp.187-197
• /
• 2010

Carbon dioxide Capture and Storage(CCS) is regarded as one of the most promising options to response climate change. CCS is a three-stage process consisting of the capture of carbon dioxide($CO_2$), the transport of $CO_2$ to a storage location, and the long term isolation of $CO_2$ from the atmosphere for the purpose of carbon emission mitigation. Up to now, process design for this $CO_2$ marine geological storage has been carried out mainly on pure $CO_2$. Unfortunately the $CO_2$ mixture captured from the power plants and steel making plants contains many impurities such as $N_2$, $O_2$, Ar, $H_2O$, $SO_2$, $H_2S$. A small amount of impurities can change the thermodynamic properties and then significantly affect the compression, purification, transport and injection processes. In order to design a reliable $CO_2$ marine geological storage system, it is necessary to analyze the impact of these impurities on the whole CCS process at initial design stage. The purpose of the present paper is to compare and analyse the relevant physical property models including BWRS, PR, PRBM, RKS and SRK equations of state, and NRTL-RK model which are crucial numerical process simulation tools. To evaluate the predictive accuracy of the equation of the state for $CO_2-SO_2$ mixture, we compared numerical calculation results with reference experimental data. In addition, optimum binary parameter to consider the interaction of $CO_2$ and $SO_2$ molecules was suggested based on the mean absolute percent error. In conclusion, we suggest the most reliable physical property model with optimized binary parameter in designing the $CO_2-SO_2$ mixture marine geological storage process.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.12 no.3
• /
• pp.217-226
• /
• 2009

Marine geological storage of $CO_2$ is regarded as one of the most promising options to response climate change. Marine geological storage of $CO_2$ is to capture $CO_2$ from major point sources, to transport to the storage sites and to store $CO_2$ into the marine geological structure such as deep sea saline aquifer. Up to now, process design for this $CO_2$ marine geological storage has been carried out mainly on pure $CO_2$. Unfortunately the captured $CO_2$ mixture contains many impurities such as $N_2$, $O_2$, Ar, $H_2O$, $SO_x$, $H_2S$. A small amount of impurities can change the thermodynamic properties and then significantly affect the compression, purification and transport processes. In order to design a reliable $CO_2$ marine geological storage system, it is necessary to perform numerical process simulation using thermodynamic equation of state. The purpose of the present paper is to compare and analyse the relevant equations of state including PR, PRBM, RKS and SRK equation of state for $CO_2-N_2$ mixture. To evaluate the predictive accuracy of the equation of the state, we compared numerical calculation results with reference experimental data. In addition, optimum binary parameter to consider the interaction of $CO_2$ and $N_2$ molecules was suggested based on the mean absolute percent error. In conclusion, we suggest the most reliable equation of state and relevant binary parameter in designing the $CO_2-N_2$ mixture marine geological storage process.

• Journal of Elementary Mathematics Education in Korea
• /
• v.9 no.2
• /
• pp.85-110
• /
• 2005

The purpose of this study is to examine the characteristics of visual representation used in problem solving process and examine the representation types the students used to successfully solve the problem and focus on systematizing the visual representation method using the condition students suggest in the problems. To achieve the goal of this study, following questions have been raised. (1) what characteristic does the representation the elementary school students used in the process of solving a math problem possess? (2) what types of representation did students use in order to successfully solve elementary math problem? 240 4th graders attending J Elementary School located in Seoul participated in this study. Qualitative methodology was used for data analysis, and the analysis suggested representation method the students use in problem solving process and then suggested the representation that can successfully solve five different problems. The results of the study as follow. First, the students are not familiar with representing with various methods in the problem solving process. Students tend to solve the problem using equations rather than drawing a diagram when they can not find a word that gives a hint to draw a diagram. The method students used to restate the problem was mostly rewriting the problem, and they could not utilize a table that is essential in solving the problem. Thus, various errors were found. Students did not simplify the complicated problem to find the pattern to solve the problem. Second, the image and strategy created as the problem was read and the affected greatly in solving the problem. The first image created as the problem was read made students to draw different diagram and make them choose different strategies. The study showed the importance of first image by most of the students who do not pass the trial and error step and use the strategy they chose first. Third, the students who successfully solved the problems do not solely depend on the equation but put them in the form which information are decoded. They do not write difficult equation that they can not solve, but put them into a simplified equation that know to solve the problem. On fraction problems, they draw a diagram to solve the problem without calculation, Fourth, the students who. successfully solved the problem drew clear diagram that can be understood with intuition. By representing visually, unnecessary information were omitted and used simple image were drawn using symbol or lines, and to clarify the relationship between the information, numeric explanation was added. In addition, they restricted use of complicated motion line and dividing line, proper noun in the word problems were not changed into abbreviation or symbols to clearly restate the problem. Adding additional information was useful source in solving the problem.

• The Journal of Korean Academy of Prosthodontics
• /
• v.50 no.4
• /
• pp.258-270
• /
• 2012

Purpose: Use of inappropriate statistical methods may lead to incorrect conclusions and a waste of valuable resources. The goal of this study was to assess the frequency and the types of several common statistical errors in the published articles of the Journal of the Korean Academy of Prosthodontics (JKAP) for a 5-year period. Materials and methods: Of 336 articles in the JKAP published from 2006 to 2010, 255 articles using statistics were reviewed and classified by statistical method and year. The frequency and types of the statistical methods were examined, and the statistical errors were evaluated by the appropriateness of the experimental design, assumption check, independent outcomes, proper sample size and suitable use of statistical method. Statistical guidelines were completed based on the appropriateness. Results: Of the 255 articles using statistics, 193 articles (75.9%) used inferential statistics and 153 articles used SPSS statistical software (60.0%). Of the articles using inferential statistics, the three most frequently used statistical methods were ANOVA (41.5%), t-test (20.0%), and the nonparametric method (16.9%). The average rate of statistical errors was 61.2 percent, similar to the rate reported by several studies completed for the medical journal. Conclusion: After the whole analysis of the difference among the groups, post-hoc tests for the pairwise comparisons are required. The optimal sample size calculation is an essential part of this study protocol. To minimize the occurrence of statistical errors, statistical guidelines were developed according to each statistical test procedure and will contribute to the academic improvement in the JKAP.

• Korean Journal of Construction Engineering and Management
• /
• v.16 no.6
• /
• pp.63-72
• /
• 2015

The importance of the appropriate use and procurement of Safety and Health Expense has been increasing along with the recent increase of construction projects in height, size and complexity. However, the current standards for deducting the Safety and Health Expense have shown limitations in applying the properties and environment of the construction project due to its Safety and Health Expense Rate's classification method. Therefore, the purpose of this study is to develop a prediction model for the Safety and Health Expense that enables the consideration of different environment and properties of construction projects. The study uses multiple regression analysis to analyze the Safety and Health Expense of Ordinary(A) of less than 0.5 billion WON. The research results have shown that the use of multiple regression analysis reduces the error rate to 4.38% which the current standard calculation method have shown 18.48%. Therefore, the use of the suggested model provides reliable Safety and Health Expense prediction values that considers the properties of the project. It is expected that the results of this study contributes to the effective safety management by providing the appropriate amount of Safety and Health Expense to the project. In this study, only projects of less than 5 billion WON have been considered in the analysis. Therefore, more data is required for future studies to suggest an overall Safety and Health Expense predict ion model that covers the whole construction industry.