• Current Optics and Photonics
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• v.2 no.6
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• pp.595-605
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• 2018

The two-photon process of microscopy provides good spatial resolution and optical sectioning ability when observing quasi-static endogenous fluorescent tissue within an in vivo animal model skin. In order to extend the use of such systems, we developed a two-photon laser scanning microscopy system capable of also capturing $512{\times}512$ pixel images at 90 frames per second. This was made possible by incorporating a 72 facet polygon mirror which was mounted on a 55 kRPM motor to enhance the fast-scan axis speed in the horizontal direction. Using the enhanced temporal resolution of our high-speed two-photon laser scanning microscope, we show that rapid processes, such as fluorescently labeled erythrocytes moving in mouse blood flow at up to 1.2 mm/s, can be achieved.

• Molecules and Cells
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• v.23 no.2
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• pp.132-137
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• 2007

With the advance of stem cell transplantation research, in vivo cell tracking techniques have become increasingly important in recent years. Magnetic resonance imaging (MRI) may provide a unique tool for non-invasive tracking of transplanted cells. Since the initial findings on the stem cell migration by MRI several years ago, there have been numerous studies using various animal models, notably in heart or brain disease models. In order to develop more reliable and clinically applicable methodologies, multiple aspects should be taken into consideration. In this review, we will summarize the current status and future perspectives of in vivo cell tracking technologies using MRI. In particular, use of different MR contrast agents and their detection methods using MRI will be described in much detail. In addition, various cell labeling methods to increase the sensitivity of signals will be extensively discussed. We will also review several key experiments, in which MRI techniques were utilized to detect the presence and/or migration of transplanted stem cells in various animal models. Finally, we will discuss the current problems and future directions of cell tracking methods using MRI.

• Journal of the Optical Society of Korea
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• v.15 no.1
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• pp.74-77
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• 2011

We report a novel extension of 840 nm wavelength- based spectral domain optical tomography to in vivo/real-time human middle ear diagnosis. The system was designed to access the middle ear region with a specifically dedicated handheld probe. The real-time displaying feature was mandatory for in vivo imaging human subject with the handheld probe, and the system could provide about 20 frames per second for 2048 pixels by 1000 A-scans without using any graphics process units under the Labview platform. The inner ear structure of a healthy male volunteer was imaged with the developed system with the axial and lateral resolutions of $15\;{\mu}m$ and $30\;{\mu}m$, respectively. The application of the OCT technology to early diagnose otitis media(OM) is very promising and could be another extensive branch in the OCT field because it provides the depth resolved image including tympanic membrane (TM) and structures below TM whereas the conventional otoscope technique only gives asurface image of the TM.

• Imaging Science in Dentistry
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• v.50 no.3
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• pp.199-208
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• 2020

Purpose: This study was performed to introduce an in vivo hybrid multimodality technique involving the coregistration of micro-computed tomography (micro-CT) and high-resolution magnetic resonance imaging (HR-MRI) to concomitantly visualize and quantify mineralization and vascularization at follow-up in a rat model. Materials and Methods: Three adult female rats were randomly assigned as test subjects, with 1 rat serving as a control subject. For 20 weeks, the test rats received a weekly intravenous injection of 30 ㎍/kg zoledronic acid, and the control rat was administered a similar dose of normal saline. Bilateral extraction of the lower first and second molars was performed after 10 weeks. All rats were scanned once every 4 weeks with both micro-CT and HR-MRI. Micro-CT and HR-MRI images were registered and fused in the same 3-dimensional region to quantify blood flow velocity and trabecular bone thickness at T0 (baseline), T4 (4 weeks), T8 (8 weeks), T12 (12 weeks), T16 (16 weeks), and T20 (20 weeks). Histological assessment was the gold standard with which the findings were compared. Results: The histomorphometric images at T20 aligned with the HR-MRI findings, with both test and control rats demonstrating reduced trabecular bone vasculature and blood vessel density. The micro-CT findings were also consistent with the histomorphometric changes, which revealed that the test rats had thicker trabecular bone and smaller marrow spaces than the control rat. Conclusion: The combination of micro-CT and HR-MRI may be considered a powerful non-invasive novel technique for the longitudinal quantification of localized mineralization and vascularization.

• Proceedings of the Korean Society of Veterinary Clinics Conference
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• 2009.04a
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• pp.307-307
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• 2009

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.372.1-372.1
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• 2016

Recently, there are a lot of diseases all around the world. Out of them, Atherosclerosis (AS) is the most common cause of stroke, cardiovascular mortality, and myocardial infarction. The macrophage-derived foam cell, which is formed by oxidized low-density lipoprotein (oxLDL), is the crucial marker for AS. In this study, we report a label-free capacitance imaging technique with multi-electrode array (MEA). The lipid-rich aorta arch lesions, which are derived from an apolipoprotein-E receptor-deficient (apoE-/-) mouse, exhibit higher capacitance than the lipid-free aorta arch, allowing the capacitance imaging of lipid region in atherosclerosis. To improve the contacts between MEA and tissue, polypyrrole(PPy)-coated multi walled carbon nanotubes (MWNTs) multi electrode array (PPy-MWNTs-MEA) was fabricated. Compared to TiN-MEA, PPy-MWNTs-MEA yielded lower contact impedance and better capacitance images. In addition, we have also developed a flexible MEA using single walled carbon nanotubes on a PET substrate. The lipid region could be discriminated in the capacitance images of the lipid-rich aorta arch lesions measured using flexible MEA, demonstrating a feasibility of in vivo applications.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1693-1696
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• 2004

Synchrotron X-ray micro-imaging technique was employed to monitor non-invasively the refilling process of water inside the xylem vessels in bamboo leaves. The consecutive phase-contrast X-ray images clearly show both plant anatomy and the transport of water inside the xylem vessels. Traces of water-rise, vapor bubbles and variations of contact angle between the water front and the xylem wall were measured in real time. During the refilling process, air bubbles are removed when the rising water front halts at a vessel end for a while. Subsequently, it starts rising again at a higher velocity than the normal refilling speed. Repeated cavitation seems to deteriorate the refilling ability in xylem vessels. In dark environment, the water refilling process in xylem vessels is facilitated more effectively than in bright illuminated conditions. Finally, X-ray micro-imaging was famed to be a powerful, high resolution, real time imaging tool to investigate the water refilling process in xylem vessels.

• Journal of Biomedical Engineering Research
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• v.28 no.1
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• pp.102-107
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• 2007

In molecular imaging studies via magnetic resonance imaging, in vivo cell tracking is an important issue for the observation of cell therapy or disease behavior. High resolution imaging and longitudinal study are necessary to track the cell movement. Since the field inhomogeneity extends over several voxels, we have performed the numerical analysis using the sub-voxel method dividing a voxel of MR image into several elements and the information about the field inhomogeneity distribution around the micro-beads. We imbedded ferrite-composite micro-beads with the size of $20-150{\mu}m$ in the subject substituted for cells to induce local field distortion. In the phantom imaging with the isotropic voxel size of $200{\mu}m^3$, we could confirm the feasibility of sub-voxel tracking in a 3.0 T MRI.

• Imaging Science in Dentistry
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• v.51 no.1
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• pp.63-71
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• 2021

Purpose: The aim of this study was to assess the artefacts of 12 fixed orthodontic appliances in magnetic resonance images obtained using 1.5-T and 3-T scanners, and to evaluate different imaging sequences designed to suppress metal artefacts. Materials and Methods: In vitro, study casts of 1 adult with normal occlusion were used. Twelve orthodontic appliances were attached to the study casts and scanned. Turbo spin echo (TSE), TSE with high readout bandwidth, and TSE with view angle tilting and slice encoding for metal artefact correction were used to suppress metal artefacts. Artefacts were measured. In vivo, 6 appliances were scanned: 1) conventional stainless-steel brackets; 2) nickelfree brackets; 3) titanium brackets; 4) a Herbst appliance; 5) a fixed retainer; and 6) a rapid maxillary expander. The maxilla, mandible, nasopharynx, tongue, temporomandibular joints, and cranial base/eye globes were assessed. Scores of 0, 1, 2, and 3 indicated no artefacts and minor, moderate, and major artefacts, respectively. Results: In vitro, titanium brackets and the fixed retainer created minor artefacts. In vivo, titanium brackets caused minor artefacts. Conventional stainless-steel and nickel free brackets, the fixed retainer, and the rapid maxillary expander caused major artefacts in the maxilla and mandible. Conventional stainless-steel and nickel-free brackets caused major artefacts in the eye globe (3-T). TSE with high readout bandwidth reduced image artefacts in both scanners. Conclusion: Titanium brackets, the Herbst appliance, and the fixed retainer caused minor artefacts in images of neurocranial structures(1.5-T and 3-T) when using TSE with high readout bandwidth.

• Korean Journal of Radiology
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• v.23 no.2
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• pp.189-201
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• 2022

Objective: To compare the outcomes of radiofrequency ablation (RFA) using dual switching monopolar (DSM), switching bipolar (SB), and combined DSM + SB modes at two different interelectrode distances (25 and 20 mm) in an ex vivo study, which simulated ablation of a 2.5-cm virtual hepatic tumor. Materials and Methods: A total of 132 ablation zones were created (22 ablation zones for each protocol) using three separable clustered electrodes. The performances of the DSM, SB, and combined DSM + SB ablation modes were compared by evaluating the following parameters of the RFA zones at two interelectrode distances: shape (circularity), size (diameter and volume), peritumoral ablative margins, and percentages of the white zone at the midpoint of the two electrodes (ablative margin at midpoint, AMm) and in the electrode path (ablative margin at electrode path, AMe). Results: At both distances, circularity was the highest in the SB mode, followed by the DSM + SB mode, and was the lowest in the DSM mode. The circularity of the ablation zone showed a significant difference among the three energy groups (p < 0.001 and p = 0.002 for 25-mm and 20-mm, respectively). All size measurements, AMm, and AMe were the greatest in the DSM mode, followed by the DSM + SB mode, and the lowest were with the SB mode (all statistically significant). The white zone proportion in AMm and AMe were the greatest in the SB mode, followed by the DSM + SB mode and DSM in general. Conclusion: DSM and SB appear to be complementary in creating an ideal ablation zone. RFA with the SB mode can efficiently eradicate tumors and create a circular ablation zone, while DSM is required to create a sufficient ablative margin and a large ablation zone.