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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.
Synthesis and Biological Activity of Conformationally Controlled 2-PAM Derivatives
Jahng, Yurngdong,Park, Jae Gyu,Yu, Jung Whey,Kim, Sun Young,Kim, Taean,Yang, Jae Ho 영남대학교 약품개발연구소 2000 영남대학교 약품개발연구소 연구업적집 Vol.10 No.-
A series of conformationally controlled 2-PAM derivatives were prepared from 2-acetylpyridine and 2,3-pyrido[b]cycloalkenones in two steps and their reactivities towards parathion poisoned AChE were evaluated. The most planar 2,3-pyrido[b]cyclohexanone oxime methiodide showed an activity comparable to 2-PAM implying E-syn is that the most active comformation of 2-PAM in the biological system.
Am Efficient Synthetic Route to Chiral $\beta$-hydroxy-$\delta$-Lactone Moiety of Compactin
Jahng, Yurng-Dong,Kim, Jin-Il The Pharmaceutical Society of Korea 1991 Archives of Pharmacal Research Vol.14 No.2
A new synthetic sequence for the chiral lactone moiety of compactin was developed from $\alpha$-D-glucose in 9 steps via simultaneous reductive detosylation and epoxide-ring opening of 2, 3-epoxy-4-tosylate using NaBH_4$ to afford 2, 4-dideoxy sugar as a key intermediate.
Jahng, Geon-Ho,Xu, Songfan Springer New York LLC 2012 BRAIN IMAGING AND BEHAVIOR Vol.6 No.3
<P>Recent studies with positron emission tomography (PET) using the Pittsburgh compound B (PIB) found widespread amyloid plaque depositions in patients with Alzheimer's disease (AD) and mild cognitive impairment (MCI) and even in cognitively normal (CN) subjects. The aim of this study was to investigate whether the local susceptibility gradients in brain tissue alter regional diffusion measurements using MRI in patients with AD and MCI. Two diffusion tensor (DT)-MRI data sets were acquired with alternating polarities of the external diffusion-sensitizing gradients. Three subject groups were included: 15 patients with AD, 18 patients with MCI and 16 CN. Maps of mean diffusivity (MD) and fractional anisotropy (FA) were computed separately for positive (p) and negative (n) polarities (pMD and nMD, pFA and nFA). Voxel-wise paired t-tests were performed between pMD versus nMD or between pFA versus nFA maps, separately for each subject group. We also investigated regions-of-interest (ROIs) in the brain. Based on the pair-wise comparisons, we found significant differences between pMD and nMD in all three groups. Results of ROI-based analyses showed that the non-linear behaviors of the ROI data sets were shown for all three groups. In conclusion, significant differences of MD maps between the two polarities of diffusion-sensitizing gradients were found, suggesting that the intrinsic background gradients may alter MD signals in specific regions. It can be important to take into account the effects of local gradient alterations during diffusion measurements in patients with AD, MCI and elderly controls.</P>
Reaction of Ru( tpy)Cl₃ with N,N,C-Terdentates, 3,2'-Annulated-6-(2"-pyridyl)-2-phenylpyridines
Jahng, Yurngdong,Park, Jae Gyu 영남대학교 약품개발연구소 2000 영남대학교 약품개발연구소 연구업적집 Vol.10 No.-
The reactions of Ru(tpy)CI_(3)(tpy=2.2';6',2"-terpyridine) with new N, N, C-terdentate ligands, 3,2'-annulated-6-(2"-pyridyl)-2-phenylpyridines(1,HL) and the properties of their Ru(Ⅱ) complexes are described. The distri-bution ratio of the two possible Ru(Ⅱ) complexes, a pentaaza-coordinated complex [Ru(tpy)(1-N,N')CI]^(+) and a cycloruthenated complex [Ru(tpy)(La-N,N',C)]^(+) are highly dependent on the length of the polymethylene unit. The trimethylene bridge of the N,N,C-terdentate in pentaaza-coordinated complex is rigid enough to induce an asymmetry in the complex.
Copper(Ⅰ) Complexes of 3,3'-Bridged 2,2'-Biquinoline-Synthesis, Properties, and Structure
Jahng, Yurngdong,Hazelrigg, John,Kimball, David,Riesgo, Elvira,Wu, Feiyue,Thummel, Randolph P. 영남대학교 약품개발연구소 1998 영남대학교 약품개발연구소 연구업적집 Vol.8 No.-
A series of 3, 3'-bridged derivatives of 2, 2'-biquinoline have been prepared where the bridge consists of one to four methylene units or a -CH=CH- moiety. The corresponding [CuL₂](ClO₄) complexes were also prepared and their structures analyzed and confirmed by ¹H NMR. Electronic absorption maxima for the metal-to-ligand transition were found to move to higher energy and oxidation potentials were found to increase as the ligands became more distorted from planarity. An X-ray analysis was carried out for the most distorted systcm having a 3, 3'-tetramethylene bridge (C_(44)H_(36)BCuF₄N₄: triclinic, P??, a = 11.605(2) Å, b = 12.622(3) Å, c = 14.524(3) Å, α = 106.05(1)˚, β = 109.06(1)˚, r = 105.37(1)˚, V = 1778 ų, Z = 2). A wide variation in Cu-N bond lengths, 1.98-2.23 Å, was observed, and the two more weakly complexed quinolines were seen to be arranged in an almost parallel fashion. Ligand exchange studies with neocuproine indicated that the strength of Cu(I) binding depends on the planarity of the system as well as the cisoid disposition of the quinoline nitrogens.
Formation of Ruthenium(Ⅱ) Complexes with Unsymmetrical Terdentate Ligands
Jahng, Yurngdong,Thummel, Randolph P.,Bott, Simon G. 영남대학교 약품개발연구소 1997 영남대학교 약품개발연구소 연구업적집 Vol.7 No.-
Three unsymmetrical terdentate ligands, 2-(2'-quinolyl)-1.10-phenanthroline (4), 2-(1'-isquinolyl)-1.10-phenanthroline (5), and 3.3'-dimethylene-2-(2'-quinolyl)-1.10-phenanthroline (6), have been prepared by application of the Friedlander condensation. Ligand 4 forms predominantly a pentaaza-coordinated (N5) complex with Ru(Ⅱ), [Ru(4-N,N,N')(4-N,N)Cl](PF_(6), whose structure was determined by X-ray analysis (C₄₂H_(26)CIF_(6)N_(6)PRu: monoclinic, C2lc, a=29.308(3) A, b=15.295(2) A, c=19.505(2) A, β=107.312(8)˚, V=8298(Ⅰ) A³, Z=8). Ligand 5 forms predominantly a hexaaza-coordinated (N6) complex, [Ru(5-N,N,N')₂. The bridged species 6 shows intermediate behavior, and the rate for interconversion of the N5 to N6 complex has been measured. The stereochemical features of these two binding modes are examined, and both π-stacking and steric effects are invoked to explain the observed behavior, leading to the proposal of a backside displacement mechanism for their interconversion.