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- 저자 : Choonsik Lee (검색결과 32 건)
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Lee, Choonsik,Yeom, Yeon Soo,Griffin, Keith,Lee, Choonik,Lee, Ae-Kyoung,Choi, Hyung-do The Korean Association for Radiation Protection 2020 방사선방어학회지 Vol.45 No.2
Background: Dose conversion coefficients (DCCs) have been commonly used to estimate radiation-dose absorption by human organs based on physical measurements of fluence or kerma. The International Commission on Radiological Protection (ICRP) has reported a library of DCCs, but few studies have been conducted on their applicability to non-Caucasian populations. In the present study, we collected a total of 8 Korean pediatric and adult voxel phantoms to calculate the organ DCCs for idealized external photon-irradiation geometries. Materials and Methods: We adopted one pediatric female phantom (ETRI Child), two adult female phantoms (KORWOMAN and HDRK Female), and five adult male phantoms (KORMAN, ETRI Man, KTMAN1, KTMAN2, and HDRK Man). A general-purpose Monte Carlo radiation transport code, MCNPX2.7 (Monte Carlo N-Particle Transport extended version 2.7), was employed to calculate the DCCs for 13 major radiosensitive organs in six irradiation geometries (anteroposterior, posteroanterior, right lateral, left lateral, rotational, and isotropic) and 33 photon energy bins (0.01-20 MeV). Results and Discussion: The DCCs for major radiosensitive organs (e.g., lungs and colon) in anteroposterior geometry agreed reasonably well across the 8 Korean phantoms, whereas those for deep-seated organs (e.g., gonads) varied significantly. The DCCs of the child phantom were greater than those of the adult phantoms. A comparison with the ICRP Publication 116 data showed reasonable agreements with the Korean phantom-based data. The variations in organ DCCs were well explained using the distribution of organ depths from the phantom surface. Conclusion: A library of dose conversion coefficients for major radiosensitive organs in a series of pediatric and adult Korean voxel phantoms was established and compared with the reference data from the ICRP. This comparison showed that our Korean phantom-based data agrees reasonably with the ICRP reference data.
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Lee, Choonsik,Lee, Choonik,Park, Sang-Hyun,Lee, Jai-Ki Published for the American Association of Physicis 2006 Medical physics Vol.33 No.2
<P>Following the previously developed Korean tomographic phantom, KORMAN, two additional whole-body tomographic phantoms of Korean adult males were developed from magnetic resonance (MR) and computed tomography (CT) images, respectively. Two healthy male volunteers, whose body dimensions were fairly representative of the average Korean adult male, were recruited and scanned for phantom development. Contiguous whole body MR images were obtained from one subject exclusive of the arms, while whole-body CT images were acquired from the second individual. A total of 29 organs and tissues and 19 skeletal sites were segmented via image manipulation techniques such as gray-level thresholding, region growing, and manual drawing, in which each of segmented image slice was subsequently reviewed by an experienced radiologist for anatomical accuracy. The resulting phantoms, the MR-based KTMAN-1 (Korean Typical MAN-1) and the CT-based KTMAN-2 (Korean Typical MAN-2), consist of 300 X 150 X 344 voxels with a voxel resolution of 2 X 2 X 5 mm3 for both phantoms. Masses of segmented organs and tissues were calculated as the product of a nominal reference density, the prevoxel volume, and the cumulative number of voxels defining each organs or tissue. These organs masses were then compared with those of both the Asian and the ICRP reference adult male. Organ masses within both KTMAN-1 and KTMAN-2 showed differences within 40% of Asian and ICRP reference values, with the exception of the skin, gall bladder, and pancreas which displayed larger differences. The resulting three-dimensional binary file was ported to the Monte Carlo code MCNPX2.4 to calculate organ doses following external irradiation for illustrative purposes. Colon, lung, liver, and stomach absorbed doses, as well as the effective dose, for idealized photon irradiation geometries (anterior-posterior and right lateral) were determined, and then compared with data from two other tomographic phantoms (Asian and Caucasian), and stylized ORNL phantom. The armless KTMAN-1 can be applied to dosimetry for computed tomography or lateral x-ray examination, while the whole body KTMAN-2 can be used for radiation protection dosimetry.</P>
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Choonsik Lee 대한방사선방어학회 2024 방사선방어학회지 Vol.49 No.1
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.
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Organ dose conversion coefficients in CT scans for Korean adult males and females
Choonsik Lee,Tristan Won,염연수,Keith Griffin,Choonik Lee,김광표 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.2
Dose monitoring in CT patients requires accurate dose estimation but most of the CT dose calculationtools are based on Caucasian computational phantoms. We established a library of organ dose conversioncoefficients for Korean adults by using four Korean adult male and two female voxel phantoms combinedwith Monte Carlo simulation techniques. We calculated organ dose conversion coefficients for head,chest, abdomen and pelvis, and chest-abdomen-pelvis scans, and compared the results with the existingdata calculated from Caucasian phantoms. We derived representative organ doses for Korean adultsusing Korean CT dose surveys combined with the dose conversion coefficients. The organ dose conversion coefficients from the Korean adult phantoms were slightly greater than those of the ICRP referencephantoms: up to 13% for the brain doses in head scans and up to 10% for the dose to the small intestinewall in abdominal scans. We derived Korean representative doses to major organs in head, chest, and APscans using mean CTDIvol values extracted from the Korean nationwide surveys conducted in 2008 and2017. The Korean-specific organ dose conversion coefficients should be useful to readily estimate organabsorbed doses for Korean adult male and female patients undergoing CT scans
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LUTHER AND CALVIN ON LOVE, LIBERTY AND LAW
Lee,Choonsik 牧園大學校 1977 論文集 - 牧園大學校 Vol.1 No.-
The view of moral law we have suggested is consistent with both the primacy of Christian love and the privilege of Christian liberty. We must not forget, however, that we cannot fulfill the moral law without love and that love can be bestowed upon us only by grace, Moreover. it is only grace that can destroy the power of sin and restore to us the freedom to choose our highest good. Thus, both Christian love and Christian liberty spring from divine grace. Wheneer it has been forgotten, The Christian ethic has ceased to be an ethic of love and liberty and has degenerated into a form of ethical legalism by which men seek to save themselves, Whenever it has been remembered. Christians have through faith known the love which fulfills the law but fulfills it in liberty.
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신춘식(Choonsik Shin),이종성(Jongsung Lee),김희동(Heuydong Kim),Toshiaki Setoguchi 한국추진공학회 2008 한국추진공학회 학술대회논문집 Vol.2008 No.11
Numerical simulations have been carried out for a supersonic two-dimensional flow over open, rectangular cavities (length-to-depth ratios are L/D = 1.0) in order to investigate the effect of non-equilibrium condensation of moist air on supersonic flows around the cavity for the flow Mach number 1.83 at the cavity entrance. In the present computational investigation, a condensing flow was produced by an expansion of moist air in a Laval nozzle. The results obtained showed that in the case with non-equilibrium condensation for L/D = 1.0, amplitudes of oscillation in the cavity became smaller than those without the non-equilibrium condensation. Furthermore, the occurrence of the non-equilibrium condensation reduced the peaks of power spectrum density and the frequency of the flow field oscillation increased in comparison with the case of S0 = 0.
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