• 천문학회지
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• 제38권2호
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• pp.319-324
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• 2005

To date, more than 150 exo-solar planets have been observed by various methods such as spectroscopic, photometric, astrometric, gravitational lensing, pulsar timing methods. However, all these are indirect methods; they do not directly image the planets. Only free-floating planets or their 'ana-log' have been directly detected so far. Thus the next milestone is the direct imaging of any kinds of planetary mass objects orbiting around normal (young) stars, which might have been associated with protoplanetary disks, the sites of planet formation. I will describe some SUBARU efforts to detect self-luminous young giant planets as companions as well as direct imaging of the protoplanetary disks of ${\~}$100 AU size. The results of near-infrared coronagraphic imaging with adaptive optics are briefly presented on AB Aur, HD 142527, T Tau, and DH Tau. Our results demonstrate the importance of high-resolution (${\~}$0.1 arcsec) direct imaging over indirect observations such as modeling based on spectral energy distributions. The SUBARU observations are a prelude to ALMA from the morphological point of view.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1989년도 춘계학술대회
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• pp.35-37
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• 1989

A new MR angiography technique using a composite sequence for the suppression of static sample signals is proposed and verified with experiments. When the composite [$90^{\circ}-{\tau}-180^{\circ}-2{\tau}-180^{\circ}-{\tau}$] sequence is applied, the large signal from the static sample is sufficiently suppressed but the signal from fresh inflow sample of which amplitude. is observed without suppression. These properties are appropriate for angiographic applications. In this paper, a modified line scan method (Block line scan angiography) incorporated with the composite [$90^{\circ}-{\tau}-180^{\circ}-2{\tau}-180^{\circ}-{\tau}$] sequence is used to obtain flow-only images, i.e., angiograms. The block line scan method improves the resolution in the flow-direction at the expense of imaging time. With the composite sequence, there is no need for subtraction procedure as in the most conventional angiographic methods. Experimental results for a phantom and a normal volunteer with KAIS 2.0 Tesla MRI system are shown.

• Investigative Magnetic Resonance Imaging
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• 제3권2호
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• pp.159-166
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• 1999

Purpose : To evaluate the effect of rotational correlation time (${\tau}_R$) and the possible related changes of other parameters, ${\tau}_M,{\;}{\tau}_S,{\;}and{\;}(\tau}_V$ of gadolinium (Gd) chelate on T1 relaxation enhancement in two pool model. Materials and Methods : The NMRD (Nuclear Magnetic Relaxation Dispersion) profiles were simulated from 0.02 MHz to 800 MHz proton Larmor frequency for different values of rotational correlation times based on Solomon-Bloembergen equation for inner-sphere relaxation enhancement. To include both unbound pool (pool A) and bound pool (pool B), the relaxivity was divided by contribution from unbound pool and bound pool. The rotational correlation time for pool A was fixed at the value of 0.1 ns, which is a typical value for low molecular weight complexes such as Gd-DTPA in solution and ${\tau}_R$ for pool B was changed from 0.1 ns to 20 ns to allow the slower rotation by binding to macromolecule. The fractional factor of was also adjusted from 0 to 1.0 to simulate different binding ratios to macromolecule. Since the binding of Gd-chelate to macromolecule cab alter the electronic environment of Gd ion and also the degree of bulk water access to hydration site of Gd-chelate, the effects of these parameters were also included. Results : The result shows that low field profiles, ranged from 0.02 to 40 MHz, and dominated by contribution from bound pool, which is bound to macromolecule regardless of binding ratios. In addition, as more Gd-chelate bound to macromolecule, sharp increase of relaxivity at higher field occurs. The NMRD profiles for different values of ${\tau}_S$ show the enormous increase of low field profile whereas relaxivity at high field is not affected by ${\tau}_S$. On the other hand, the change in ${\tau}$V does not affect low field profile but strongly in fluences on both inflection fie이 and the maximum relaxivity value. The results shows a fluences on both inflection field and the maximum relaxivity value. The results shows a parabolic dependence of relaxivity on ${\tau}_M$. Conclusion : Binding of Gd-chelate to a macromolecule causes slower rotational tumbling of Gd-chelate and would result in relaxation enhancement, especially in clinical imaging field. However, binding to macromolecule can change water enchange rate (${\tau}_M$) and electronic relaxation ($T_le$) vis structural deformation of electron environment and the access of bulk water to hydration site of metal-chelate. The clinical utilities of Gd-chelate bound to macromolecule are the less dose requirement, the tissue specificity, and the better perfusion and intravascular agents.

• 대한방사성의약품학회지
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• 제6권1호
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• pp.27-38
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• 2020

Alzheimer's disease (AD) is one of the challenging conditions that have no cure, yet early diagnosis can help to control the disease. PET imaging of tau has several advantages, such as being a noninvasive, safe diagnostic technique that correlates directly with the disease progression. Many tau tracers have been reported to date; however, the chemical scaffolds of them fall in a narrow chemical window, and none was approved yet as none is entirely selective and sensitive to tau. These problems are being solved as new tracers emerge constantly. In this report, the first-generation tau tracers such as [¹¹C]PBB3, 2-arylquinoline (THK) series, [¹⁸F]T808, and [¹⁸F]AV-1451 ([¹⁸F]T807) are reviewed from an organic and radiochemistry perspective; thus the most effective chemical approach to synthesize these tracers is discussed. This would help to design novel tracers which can meet the challenges faced by the current tracers.

• Investigative Magnetic Resonance Imaging
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• 제3권1호
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• pp.60-65
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• 1999

목적 : 뇌백질 신호억제를 위한 중간시간 반전회복(Medium Tau Inversion Recovery, MTIR)영상에서 뇌회질과 뇌배질의 대조도를 다른 기법의 MR영상과 비교해 보고 뇌피질에 이상이 있는 환자에서 MTIR영상의 유용성을 평가하고자 하였다. 대상 및 방법 : 2명의 정상 지원자와 뇌피질 이형성증을 포함한 뇌피질 질환이 있는 21명을 대상으로 뇌회질과 뇌백질의 신호의 차이를 관심영역에서 대조도 백분율과 대조도 잡음비로 츠정하여 MTIR영상과 여러 가지 다른 MR영상을 비교하였다. 또한 시각적으로 병변이 뚜렷함, 새로운 병변의 발견여부를 시각적으로 비교 평가하였다. 결과 : MTIR영상은 다른 MR영상에 비해 대조도 백분율, 대조도 잡음비가 높아 뇌회질과 뇌백질의 신호의 차이가 가장 뚜렷하였다. 신경이주이상을 포함한 21명의 뇌피질 환자에서는 MTIR영상에서 다른 영상보다 병변이 뚜려사고 병변의 묘사(delineation)을 증가 시켰으나 새로운 병변은 발견하지 못해다. 결론 : MTIR영상은 뇌회질과 뇌백질의 대조도를 증가시키는 영상 기법이며 뇌피질을 침범한 질환을 특히 뇌피질 이형성증의 병변을 매우 잘 나타냈다. 기존의 T1강조영상 또는 3D-MPRAG에서 뇌피질-백질의 구별이 어려운 경우에는 보완적으로 이용가치가 있는 영상기법으로 생각된다.

• BMB Reports
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• 제56권12호
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• pp.657-662
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• 2023

Neurodegenerative diseases are characterized by distinct protein aggregates, such as those of α-synuclein and tau. Lysosomal defect is a key contributor to the accumulation and propagation of aberrant protein aggregates in these diseases. The discoveries of common proteinopathies in multiple forms of lysosomal storage diseases (LSDs) and the identification of some LSD genes as susceptible genes for those proteinopathies suggest causative links between LSDs and the proteinopathies. The present study hypothesized that defects in lysosomal genes will differentially affect the propagation of α-synuclein and tau proteins, thereby determining the progression of a specific proteinopathy. We established an imaging-based high-contents screening (HCS) system in Caenorhabditis elegans (C. elegans) model, by which the propagation of α-synuclein or tau is measured by fluorescence intensity. Using this system, we performed RNA interference (RNAi) screening to induce a wide range of lysosomal malfunction through knock down of 79 LSD genes, and to obtain the candidate genes with significant change in protein propagation. While some LSD genes commonly affected both α-synuclein and tau propagation, our study identified the distinct sets of LSD genes that differentially regulate the propagation of either α-synuclein or tau. The specificity and efficacy of these LSD genes were retained in the disease-related phenotypes, such as pharyngeal pumping behavior and life span. This study suggests that distinct lysosomal genes differentially regulate the propagation of α-synuclein and tau, and offer a steppingstone to understanding disease specificity.

• 대한영상의학회지
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• 제83권3호
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• pp.453-472
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• 2022

양전자방출단층촬영(PET)을 이용한 단백질병리의 생체영상기술은 퇴행성 치매의 질병 기전을 이해하는데 필요한 정보를 제공할 뿐 아니라, 질병의 조기 발견과 치료법 개발에서 중요한 역할을 수행하고 있다. 베타아밀로이드와 타우 PET 영상은 인체 뇌병리에 기반한 알츠하이머병 연속체에 대한 진단 바이오마커로 확립되어 조기진단과 감별진단을 용이하게 하고, 질병 예후를 예측하고 있다. 또한, 치매치료제 개발에서 예후 및 대리 바이오마커로의 역할이 커지고 있다. 이 종설에서는 치매를 유발하는 알츠하이머병 및 기타 퇴행성 뇌질환에서 베타아밀로이드와 타우 단백질의 뇌축적을 영상화하는 PET의 최근 임상적 적용과 최근 동향을 살펴보고, 잠재적 유용성을 소개하고자 한다.

• Molecules and Cells
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• 제41권12호
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• pp.1045-1051
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• 2018

The developmentally regulated GTP binding protein 2 (DRG2) is involved in the control of cell growth and differentiation. Here, we demonstrate that DRG2 regulates microtubule dynamics in HeLa cells. Analysis of live imaging of the plus-ends of microtubules with EB1-EGFP showed that DRG2 deficiency (shDRG2) significantly reduced the growth rate of HeLa cells. Depletion of DRG2 increased 'slow and long-lived' subpopulations, but decreased 'fast and short-lived' subpopulations of microtubules. Microtubule polymerization inhibitor exhibited a reduced response in shDRG2 cells. Using immunoprecipitation, we show that DRG2 interacts with tau, which regulates microtubule polymerization. Collectively, these data demonstrate that DRG2 may aid in affecting microtubule dynamics in HeLa cells.

• 대한치매학회지
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• 제17권3호
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• pp.110-119
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• 2018

Background and Purpose: To analyze $^{18}F-THK5351$ positron emission tomography (PET) scans of patients with clinically diagnosed nonfluent/agrammatic variant primary progressive aphasia (navPPA). Methods: Thirty-one participants, including those with Alzheimer's disease (AD, n=13), navPPA (n=3), and those with normal control (NC, n=15) who completed 3 Tesla magnetic resonance imaging, $^{18}F-THK5351$ PET scans, and detailed neuropsychological tests, were included. Voxel-based and region of interest (ROI)-based analyses were performed to evaluate retention of $^{18}F-THK5351$ in navPPA patients. Results: In ROI-based analysis, patients with navPPA had higher levels of THK retention in the Broca's area, bilateral inferior frontal lobes, bilateral precentral gyri, and bilateral basal ganglia. Patients with navPPA showed higher levels of THK retention in bilateral frontal lobes (mainly left side) compared than NC in voxel-wise analysis. Conclusions: In our study, THK retention in navPPA patients was mainly distributed at the frontal region which was well correlated with functional-radiological distribution of navPPA. Our results suggest that tau PET imaging could be a supportive tool for diagnosis of navPPA in combination with a clinical history.

• 한국지리정보학회지
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• 제16권2호
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• pp.141-151
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• 2013

본 연구에서는 MODIS 인공위성으로 분석된 에어러솔 광학두께 자료와 지상에서 관측된 시정거리 자료를 이용하여 에어러솔 연직분포 모델링을 수행하였다. 위성과 지상관측자료로부터 에어러솔의 척도 고도를 구할 수 있었으며, 그 결과는 복사전달 모델에서 사용되고 있는 표준대기 모델과 비교에서 만족할 만한 수준의 근사치를 보였다. 그리고 실제 사례로서 대기가 청명한 경우(${\tau}_{MODIS}=0.12{\pm}0.07$, 시정거리=$21.13{\pm}3.31km$)와 혼탁한 경우(${\tau}_{MODIS}=1.71{\pm}0.85$, 시정거리 =$13.33{\pm}5.66km$)에 대해서 적용하여 척도 고도를 산정한 결과는 각각 전국 평균값으로서 $0.63{\pm}0.33km$와 $1.71{\pm}0.84km$로 나타났다. 그리고 이 결과를 바탕으로 대기 에어러솔 소산계수의 연직분포를 구할 수 있었으며, 최종적으로 KML 형식으로 코딩되어 관심 영역의 대기 환경 특성 변화를 감시하는데 도움이 될 것으로 기대된다.