• Bulletin of the Korean Chemical Society
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• v.28 no.6
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• pp.909-910
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• 2007

• Journal of Pharmaceutical Investigation
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• v.39 no.6
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• pp.393-400
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• 2009

PHEA (hydroxyethyl-aspartamide)-mPEG (methoy-polyethyleneglycol)-$C_{16}$ (hexadecylamine)-ED (ethylenediamine) was prepared as a drug delivery carrier. The structure and molecular weight of polymers were characterized by $^1H$-NMR and gel permeation chromatography. Micelle size and shape were measured by electro-photometer light scattering and transmission electron microscope. The mean diameter of micelles was 23 nm in aqueous solution. To evaluate the potential of these polymeric micelles as a drug carrier, PSI-mPEG-$C_{16}$-ED was conjugated with Cy5.5 for Near-Infrared Fluorescent (NIRF) based optical imaging. PSI-mPEG-$C_{16}$-ED-Cy5.5 was injected intravenously into mice (n=5) and in vivo NIRF imaging was performed during 48 h after injection. The biodistribution study at 24 h after injection showed the longcirculation property of PSI-mPEG-$C_{16}$-ED-Cy5.5. Therefore, PSI-mPEG-$C_{16}$-ED micelles could be a promising drug carrier and imaging agent.

• Journal of Biomedical Engineering Research
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• v.30 no.6
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• pp.461-468
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• 2009

Magnetic resonance electrical impedance tomography (MREIT) enables us to perform high-resolution conductivity imaging of an electrically conducting object. Injecting low-frequency current through a pair of surface electrodes, we measure an induced magnetic flux density using an MRI scanner and this requires a sophisticated MR phase imaging method. Applying a conductivity image reconstruction algorithm to measured magnetic flux density data subject to multiple injection currents, we can produce multi-slice cross-sectional conductivity images. When there exists a local region of fat, the well-known chemical shift phenomenon produces misalignments of pixels in MR images. This may result in artifacts in magnetic flux density image and consequently in conductivity image. In this paper, we investigate chemical shift artifact correction in MREIT based on the well-known three-point Dixon technique. The major difference is in the fact that we must focus on the phase image in MREIT. Using three Dixon data sets, we explain how to calculate a magnetic flux density image without chemical shift artifact. We test the correction method through imaging experiments of a cheese phantom and postmortem canine head. Experimental results clearly show that the method effectively eliminates artifacts related with the chemical shift phenomenon in a reconstructed conductivity image.

• Korea-Australia Rheology Journal
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• v.14 no.3
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• pp.93-105
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• 2002

Experimental methods for making quantitative measurements of velocity fields in non-Newtonian fluids are reviewed. Techniques based on light scattering spectroscopy - laser Doppler velocimetry and homodyne light scattering spectroscopy, techniques based on imaging the displacement of markers - including particle image velocimetry and molecular tagging velocimetry, and techniques based on nuclear magnetic resonance imaging are discussed. The special advantages and disadvantages of each method are summarized, and their applications to non-Newtonian flows are briefly reviewed. Example data from each technique are also included.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.6 no.2
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• pp.171-176
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• 2020

Covalent organic frameworks (COFs) are porous crystalline polymers in which organic units are linked by covalent bonds and have a regular arrangement at the atomic level. Recently, the COFs have been much attention in bio-medical area such as bio-imaging, drug delivery, and therapeutics. These 2D nanoparticles are proving their value in nanomedicine due to their large surface area, functionalization through functional groups exposed on the surface, chemical stability due to covalent bonding, and high biocompatibility. The high ω-electron density and crystallinity of COFs makes it a promising candidate for bioimaging probes, and its porosity and large surface area make it possible to be utilized as a drug delivery vehicle. However, the low dispersibility in water, the cytotoxicity problems of COFs are still challenged to be solved in the future. In this regard, several efforts that increase the degree of dispersion through functionalization on the surface of COFs for the application to the biomedical field have been reported. In this review, we would like to describe the advantages and limitations of COFs for bio-imaging and anti-cancer treatment.

• Progress in Medical Physics
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• v.28 no.4
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• pp.135-143
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• 2017

Chemical Exchange Saturation Transfer (CEST) imaging is a method to detect solutes based on the chemical exchange of mobile protons with water. The solute protons exchange with three different patterns, which are fast, slow, and intermediate rates. The CEST contrast can be obtained from the exchangeable protons, which are hydroxyl protons, amine protons, and amide protons. The CEST MR imaging is useful to evaluate tumors, strokes, and other diseases. The purpose of this study is to review the mathematical model for CEST imaging and for measurement of the chemical exchange rate, and to measure the chemical exchange rate using a 3T MRI system on several amino acids. We reviewed the mathematical models for the proton exchange. Several physical models are proposed to demonstrate a two-pool, three-pool, and four-pool models. The CEST signals are also evaluated by taking account of the exchange rate, pH and the saturation efficiency. Although researchers have used most commonly in the calculation of CEST asymmetry, a quantitative analysis is also developed by using Lorentzian fitting. The chemical exchange rate was measured in the phantoms made of asparagine (Asn), glutamate (Glu), ${\gamma}-aminobutyric$ acid (GABA), glycine (Gly), and myoinositol (MI). The experiment was performed at a 3T human MRI system with three different acidity conditions (pH 5.6, 6.2, and 7.4) at a concentration of 50 mM. To identify the chemical exchange rate, the "lsqcurvefit" built-in function in MATLAB was used to fit the pseudo-first exchange rate model. The pseudo-first exchange rate of Asn and Gly was increased with decreasing acidity. In the case of GABA, the largest result was observed at pH 6.2. For Glu, the results at pH 5.6 and 6.2 did not show a significant difference, and the results at pH 7.4 were almost zero. For MI, there was no significant difference at pH 5.6 or 7.4, however, the results at pH 6.2 were smaller than at the other pH values. For the experiment at 3T, we were only able to apply 1 s as the maximum saturation duration due to the limitations of the MRI system. The measurement of the chemical exchange rate was limited in a clinical 3T MRI system because of a hardware limitation.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2003.09a
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• pp.72-72
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• 2003

Purpose: To prove feasibility of proton chemical shift imaging (lH CSI) during stereotactic procedure, authors performed IH CSI in combination with a stereotactic headframe and selected targets according to local metabolic information, evaluated the pathologic results. Methods: The 1H CSI directed stereotactic biopsy was performed in five patients. 1H CSI was performed before conventional stereotactic MRI with gadolinium enhancement for stereotactic coordinates. The metabolite images expressed as integral ratios, Cho/Cr and Lac/Cr, were displayed in different colors. The stereotactic target coordinates were correlated with the coordinates from the 1H CSI images. Results: The final pathologic results obtained were concordant with the local metabolic information from 1H CSI. We believe that 1H CSI-directed stereotatic biopsy has the potential to significantly improve the accuracy of stereotactic biopsy targeting. Conclusions : Metabolic signals derived from 1H CSI could give us more direct clues for stereotactic target selection during the subsequent conventional stereotactic MR imaging. 1H CSI was feasible with the stereotatic headframe in place. The final pathologic results obtained were concordant with the local metabolic information from 1H CSI. Acknowledgement: This study was supported by a grant of the Center for Functional and Metabolic Imaging Technology, Ministry of Health & Welfare, Republic of Korea (02-PJ3-PG6-EV07-0002).

• Bulletin of the Korean Chemical Society
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• v.31 no.12
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• pp.3693-3696
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• 2010

We experimentally measure the kinetic energy and angular distributions of photoelectrons of $N_2$ as a function of 410 nm femtosecond laser intensity by using velocity map imaging technique. The strong-field multiphoton ionization of molecules shares many of the characteristics with those of atoms. Electron kinetic energies are nearly independent of laser intensities. The independence suggests that the electron peaks in the photoelectron spectrum actually result from a two-step process, indicative of the occurrence of real population in the intermediate states. The relative amplitudes of electron peaks indicate that in the two-step process, nonresonant population transfer dominates for low intensities, while resonant population transfer dominates for higher intensities.

• Bulletin of the Korean Chemical Society
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• v.34 no.3
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• pp.957-959
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• 2013

• Journal of Yeungnam Medical Science
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• v.4 no.1
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• pp.1-15
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• 1987

Magnetic Resonance (M.R.) is rapidly emerging technique that provides high quality images and potentially provides much more diagnostic information than do conventional imaging modalities. M.R.I. is conceptually quite different from currently used imaging methods. The complex nature of M.R.I. allows a great deal of flexibility in image product ion and available information, and key points are as follows. 1. M.R.I. offers a non-invasive technique with which to gene rate in vivo human images without ionizing radiation and with no known adverse biological effects. 2. Imaging mechanism of M.R.I. is quite different from conventional imaging modality and for more accurate diagnostic application, It is necessary for physician to understand imaging mechanism of M.R.I. 3. M.R. makes available basic chemical parameters that may provide to be useful for diagnostic medical imaging and more specific pathophysiologic information which are not available by alternate techniques. 4. M.R. can be produced by number of different methods. This flexibility allows the imaging technique to be applicated for particular clinical purpose. Multiplanar and three dimensional imaging may extend the imaging process beyond the single section available with current CT. 5. Future directions include efforts to; a. Further development of hard ware b. More fasternning scan time c. Respiratory and cardiac gated imaging d. Imaging of additional nuclei except hydrogen e. Further development of contrast media f. M.R. in vivo spectroscopy g. Real time M.R. imaging.