Magnetic Resonance Imaging: Historical Overview, Technical Developments, and Clinical Applications

Jahng, Geon-Ho,Park, Soonchan,Ryu, Chang-Woo,Cho, Zang-Hee Korean Society of Medical Physics 2020 의학물리 Vol.31 No.3

The authors congratulate the cerebrations for the 30 years of the Korean Society of Medical Physics (http://www.ksmp.or.kr/). The paper is published to recognize the anniversary. Geon-Ho Jahng invited Professor Z. H. Cho to join to submit this manuscript because he has been one of the leaders in the field of magnetic resonance imaging (MRI) during the last 40 years. In this review, we describe the development and clinical histories of MRI internationally and domestically. We also discuss diffusion and perfusion MRI, molecular imaging using MRI and MR spectroscopy (MRS), and the hybrid systems, such as positron emission tomography-MRI (PET-MRI), MR-guided focused ultrasound surgery (MRgFUS), and MRI-guided linear accelerators (MRI-LINACs). In each part, we discuss the historical evolution of the developments, technical developments, and clinical applications.

The Antioxidant Effect of the Rhaponticum uniflorum Extracts on the Oxidative Stress in H₂O₂ induced Human Keratinocytes

So Hee Ahn,Won Yeoung Choi,Ji Won Jeong,Geon Woo Park,Su Yeon Kang,Eun Jeong Kim,Su Rim Sin,Eun Seo Jang,Gye Won Lee,Young Ho Cho 한국식품영양과학회 2021 한국식품영양과학회 학술대회발표집 Vol.2021 No.10

In this study, To investigate the antioxidant activities of Rhaponticum uniflorum extracts (RUE), we assessed scavenging activities on DPPH, ABTS radicals, and reducing power. The DPPH and ABTS radical scavenging activities (SC50) of RUE were 96.97±1.19 μg/mL and 31.26±0.13 μ g/mL, respectively, and the reducing power significantly increased dose-dependent manner. To study the antioxidant effecters of RUE in H₂O₂ induced human keratinocytes, expression of Nuclear factor erythroid-2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) were determined by Western blot and qRT-PCR. RUE induced the expression of HO-1, a critical target enzyme of Nrf2, in a concentration-dependent manner. The expression of HO- 1 mRNA was also induced in H₂O₂-treated HaCaT cells but no significant difference in the level of HO-1 mRNA was observed. Taken together, these results suggest that RUE may be useful as a potential ingredient for anti-aging products.

절연 파괴 특성을 이용한 에폭시 복합체의 절연 신뢰도 예측

박건호,이준웅 광운대학교 신기술연구소 1996 신기술연구소논문집 Vol.25 No.-

본 연구에서는 송배전 계통에서 변성기의 몰드 재료로서 널리 사용되고 있는 에폭시 수지를 시료로 하여 설정해 높은 배합비에 따라 5종으로 제작한 각 시편에 대해 절연 파괴 실험을 하였다. 절연파괴 데이터를 가지고 와이블 분포식을 이용하여 임의의 허용 파괴 확률에서의 허용인가 전계의 값을 추정하였으며 절연 안전성을 판단하기 위하여 경년 열화(經年劣化) 데이터의 통계 처리를 행한 결과 허용 파괴 확률을 0.1[%]로 하였을 때, 허용 인가 전계는 21.5[kV/mm] 이하가 되어야 함을 확인할 수 있었다. In this study, the dielectric breakdown of epoxy composites used for transformers was experimented and then its data were simulated by Weibull distribution probability. The more hardener increased the stronger breakdown strength at low temperature because of cross-linked density by the virtue of ester radical, and the breakdown strength of specimens with filler was lower than it of non-filler specimens because it is believed that the adding filler forms interface and charge is accumulated in it, therefore the molecular motility is raised, the electric field is concentrated, and the acceleration of electron and the growth of electron avalanche are early accomplished. From the analysis of Weibull distribution, it was confirmed that as the allowed breakdown probability was given by 0.1[%], the applied field value needed to be under 21.5[kV/mm].

定期船 海運의 運賃決定要因과 安定化方案에 관한 硏究

박호건,안기명 한국해운물류학회 2002 해운물류:이론과실천 Vol.- No.3

정기선 해상운송과 관련 운임 결정에 있어서 경제 이론적, 경영 과학적 접근방법과 카르텔 형태인 해운동맹 등을 통하여 인위적이고 물리적인 방법 하에 적정운임 결정을 도출하려는 연구가 이루어져 왔으나 현대조선 기술의 발달과 단위당 비용 절감을 통해 규모의 경제를 실현하고져 계속되는 초대형 컨테이너 선박의 건조는 제한된 정기선 시장에 만성적인 선복 공급 과잉이 되어 극심한 경쟁으로 기존 운임시장이 교란되어 원가이하의 운임 수입으로 해운기업들의 통폐합 또는 존폐문제로 귀결되고 있으며, 더욱이 정기선 시장의 불안정과 운임의 극심한 편차는 궁극적으로 안정된 국제 상품 교역에 위해 요소로 작용하고 있는바 이와 관련 정기선 시장의 운임에 영향을 미치는 요인을 실증 분석하여 그 대책과 방안을 제시하여 정기선 시장의 질서 유지와 운임 안정화를 도모하는데 연구목적을 두고져한다. The global liner shipping markets have changed significantly since year 1990 especially in containerized liner freights. The number of liner containers has increased steadily to about 6-12 percent every year and KMI forecasted global container movements in year 2002 as 248 million TEU showing 142% up on 103 million TEU in year 1992. As well, the number of container vessels and its loading capacity have increased drastically for the purpose of contributing to the increase in worldwide demand for liner freights and the existence of economies of vessel size. KMI reported that the global loading capacity of container fleets will be estimated as 5.5 million TEU showing 150% up on 2.2 million TEU in year 1992 and the size of vessel to be ordered by global carriers become bigger and larger to Post/Super panamax model of 6,000-8,000 TEU capacity as fifth to seventh generation type. Ultimately, the trend to more and larger ships has been accompanied by strong growth in available liner capacity. Most of trade routes have been oversupplied with ship slots and reported that the surplus ratio of ship's slots will be around 24.5% in year 2002 and further estimated excess capacity of 30-40% in the Trans- pacific and the Europe trade. Eventually, such excess capacity in liner shipping is a result of increased competition among the carriers, in which appears to have led to a quest for lower freight rates and lower costs. In turn the liner market has been extremely unstabilized by intense and unfair competition each other and the profitability of liner carries become poor and lower and such low profits may be a force driving toward strategies involving alliances, mergers and building bigger ships in an effort to capture economics of scale and scope. To make it worse, some of carriers having financial difficulties have finally gone to the bankruptcy. Accordingly, the primary objective of this thesis is to explain the determinant of the freight rates theoretically and practically and to find out how to take an appropriate measures to be stabilized for liner markets and liner freight rates through the introduction of institutional and systematical approaches to the liner shipping industry.

Cao-MgO-SiO₂-P₂O -CaF₂계 생체활성 결정화 유리의 기계적 성질에 미치는 ZrO₂및 Al₂O₃의 분산 강화 효과

박찬운,강건구,원대희,이민호,배태성 대한치과기재학회 1998 대한치과재료학회지 Vol.25 No.2

Bioactive glass-ceramics can form tight chemical bonds with bone, however, their poor mechanical properties may limit their clinical applications. Alumina ceramics show good biocompatibility and high strength but can't form chemical bonds with bone. Hydroxyapatite ceramics and bioglass form chemical bonds with bone but their strength and fracture are relatively low. Glass ceramics containing apatite and wollastonite crystals can form tight chemical bonds with bone and show relatively high strength and fracture toughness. Bioactive glass-ceramics toughened by alumina and tetragonal zirconia polycrystals show relatively high mechanical strength. Both bioactive and high strength ceramics will be widely applicable to many clinical applications. In this study, bioactive glass-ceramics toughened by alumina and zirconia polycrystals were fabricated, and crystallization behavior, biaxial flexure strength, fracture toughness, and bioactivity were measured. The results obtained were summarized as follows; 1. The major crystaline phase in the matrix glass were observed to be apatite, wollastonite, and β-TCP. 2. Biaxial flexure strength and fracture toughness values were more improved by the dispersion toughening of alumina and zirconia, and the improvement of mechanical strength was more higher in the dispersion toughening of zirconia than that of alumina. 3. The bioactivity, which was evaluted from apatite formation in the simulated body fluid, was higher in the dispersion toughening of Zr-O₂than that of Al₂O₃.

급성 심근 경색증과 혈장 Paraoxonase activity와의 관계

김건영,윤상준,박근호,조영신,장성종,장경식,홍순표 조선대학교 부설 의학연구소 2000 The Medical Journal of Chosun University Vol.25 No.1

연구배경: 혈장 파라옥소나제의 감소는 HDL-cholesterol의 항 산화작용의 중요한 요소로 알려져 있어 이의 감소는 항산화작용의 저하로 인해 동맥경화의 진행을 촉진시킬 수 있어 허혈성심장병의 주요 위험인자로 추정하고 있다. 본 연구에서는 급성 심근 경색증 환자를 대상으로 혈장 파라옥소나제의 활성도를 측정하여 정상군과 비교하여 혈장 파라옥소나제 활성도의 감소가 급성 심근 경색증의 위험인자인지 알아보고자 하였다. 대상 및 방법: 급성 심근 경색증으로 입원한 39 명의 환자(남자 : 여자 = 19 : 20, 평균나이: 61±4.3세)와 정상 대조군 36명(남자 : 여자 = 17 : 19, 평균나이: 55±10세)을 대상으로 정맥혈을 채혈 후 파라옥소나제 활성도와 LDL-cholesterol, total cholesterol, HDL-cholesterol를 측정하였다. 두 군간의 비교는 Student T-test를 이용하였다. 결과: 건강 대조군과 급성 심근 경색 환자군 간에 측정치를 비교해본 결과 혈장 콜레스테롤 수치는 182.10± 12mg/dl, 194.87± 40mg/dl이고 HDL 콜레스테롤은 54±5.4mg/dl, 37.52± 13mg/dl 였다. LDL 콜레스테롤은 94.45±13mg/d1, 122±34mg/d1로 급성 심근 경색증 환자의 경우 통계학적으로 의미있는 차이를 보였다. (P<0.05). 그러나 혈장 파라옥소나제 활성도는 건강 대조군 112.35±15U/ml, 급성심근 경색증 환자군 96.10±43.50U/ml로 급성 심근 경색증 환자군이 건강 대조군에 비해 낮은 수치를 보이는 경향이 있었으나 통계학적으로 유의한 차이(P=0.071)는 보이지 않았다(Table 2참조). Background : Human plasma paraoxonase is a HDL-associated ester hydrolase that catalyzes the hydrolysis of organophosphates, aromatic carboxylic acid esters and carbamates. HDL has been implicated in the prevention of LDL lipid peroxidation. Low paraoxonase activity in the Plasma may have responsibility to the development of coronary artery disease partially because oxidized LDL has intimate relationship with atherosclerosis. We studied plasma paraoxonase activities in the plasma of acute myocardial infarction patients in order to evaluate the relationship between these enzyme activities and the acute myocardial infarction. Materials and Methods : plasma samples were obtained from 39 individuals with acute myocardial infarction(M: 19 cases, F: 20cases, mean age: 61(4.3 years) and 36 individuals of healthy control(M: 17 cases, F: 19cases, mean age: 55(10 years). We determined paraoxonase activities, total cholesterol, LDL-cholesterol &DL-cholesterol levels in the plasma samples. Paraoxonase activities were measured spectrophoto metrically in 0.1M Tris-HCl buffer (pH=7.4) at 25℃ with paraoxon as substrate(5.5mM) at 405 nm. We used student T-test to compare the results of both groups. Results : Comparison of the results between myocardial infarction patients and normal control groups revealed that plasma total cholesterol, HDL-cholesterol and LDL-cholesterol levels showed statistically significant differences between groups but plasma paraoxonase activity does not. Conclusion : Our study showed that there was no significant difference of plasma paraoxonase activity between acute myocardial infarction and normal population. So low plasma paraoxonase activity may not be a risk factor of acute myocardial infarction. but further prospective large scale study will be needed to conclude.

자해

반건호,강윤형,박태원,이은정,표경식 漢陽大學校 精神健康硏究 2000 精神健康硏究 Vol.19 No.-

급성 지주막하 출혈에 동반된 관상동맥 연축에 의한 심근경색증 1예

부귀범,박근호,양종태,이동민,장성종,김건영,장경식 조선대학교 2001 The Medical Journal of Chosun University Vol.26 No.1

In many cases, acute cerebrovascular disease is accompanied by abnormal electocardiograms. Also, though rather uncommon, acute myocardial infraction is also seen. The mechanism of its occurance is uncertain but it is thought to be related to coronary artery spasms, an abnormal autonomic nervous system, and a catecholamine increase. A female patient of 34 years of age came to the hospital because of sudden headache accompanied by substernal chest pain. A subarachnoid hemorrhage due to a cerebral aneurysm rupture had occured, and there was ST segment elevation in lead II, III, and aVF of the electrocardiogram. A cardiac enzyme test, an echocardiography, and a coronary angiography were performed, and she was diagnosed to have acute myocardial infarction due to coronary artery spasm. Clipping of the aneurysm was performed. With the use of nitrate and an angiotension converting enzyme inhibitor, the condition of the patient improved.

축차확률비 검정을 이용한 실제값과 Wald 근사값의 정확도에 관한 연구

조규민,조건호,박용우 대구대학교 산업기술연구소 1993 産業技術硏究 Vol.12 No.-

Sequential analysis refers to techniques for testing hypotheses or estimating parameters when the sample size is not fixed in advance but is determined during the course of the experiment by criteria which depend on the observations as they occur. In this paper, We considered the properties of Wald approximations in S.P.R.T. and compared exact value with the Wald approximations by using a example and then found the error probabilities α_(0),α₁and expected sample size (average sample number) E(N) by S.P.R.T in AR(1). Conclusively, We discovered that Wald approximations tend to over-estimate the true error probabilities.

방사선 조사후 아크릴릭 레진의 물성변화

이용근,이건일,박영준,변호영 원광대학교 생체재료·매식연구소 1995 원광생체재료·매식 Vol.4 No.2

To investigate the effect of high dose irradiation on the mechanical properties. dental acrylic resin specimens were irradiated and the Vickers hardness number(VHN) and the 3-point flexure strength(FS) were measured before and after irradiation. Five kinds of acrylic resins were studied. Two(VRS. PS2) were heat cured denture base resins. one(VSC) was chemically cured denture base resin and the other two(ORJ, VOP) were orthodontic resins. The acrylic resin specimens were made according to the manufacturer's instructions and were finally polished with Microcloth (Buehler). Among ten specimens of each material. five specimens were irraditated with 100 Gy using a linear accelerator (Mitsubishi 6 MV), and the others were not. The specimens were immersed in 37℃ D.W. for 48 hours before testing. Each specimens the VHN was measured 10 times. Their FS was measured with an universal testing machine (Instron 4302, England), with a cross-head speed of 5 mm/min. The VHNs of heat cured resins were 21.52∼25.55 kg/㎟ before irradiation and 19.93∼26.58 kg/㎟ after irradiation. Those of chemically cured resins were 11.28∼16.6kg/㎟ before irradiation and 11.3∼14.3 kg/㎟ after irradiation. The VHNs of heat cured acrylic resins were significantly higher than those of chemically cured resins were significantly higher than those of chemically cured resins before and after irradiation(p<0.05). VHN of VRS was significantly increased after irradiation, and those of VOP and PS2 were significantly decreased after irradiation (p<0.05). The FS of resins studied were 6.7∼8.0 kg/㎟ before irradiation and 6.5∼8.4 kg/㎟ after irradiation. The FS of VSC and VRS increased after irradiation and those of VOP, ORJ and PS2 decreased after irradiation, but the results were not statistically significant. Before irradiation, the FS of heat cured resins were somewhat higher than those of chemically cured resin, but not statistically significant, and after irradiation the FS of heat cured resins were significantly higher than those of orthodontic resins. In conclusion. high dose irradiation did not result in consistent changes in mechanical properties.