• Proceedings of the KSMRM Conference
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• 2005.09a
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• pp.28-28
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• 2005

• Proceedings of the KSMRM Conference
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• 2003.10a
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• pp.79-80
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• 2003

In existing method, the threshold has determined the points to be used in extrapolation and only pre-peak points were used to find t0. However, to reduce error in using this fitting method, in this study, finding t0is considered the correlation between fitting result and each profile in using iteration method. And the proposed method is compared with the existing method.

• Journal of the Korean neurological association
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• v.36 no.4
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• pp.399-401
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• 2018

• Investigative Magnetic Resonance Imaging
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• v.13 no.1
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• pp.81-87
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• 2009

Purpose : We sought to evaluate enhancement of plaque with gadolinium-based contrast agent by magnetic resonance imaging (MRI) in comparison with histopathology, namely lipid-rich and macrophage-rich components that were two representative characteristics of plaque vulnerability using atherosclerotic rabbit aorta in order to determine which histopathologic component is relevant to the enhancement. Materials and Methods : New Zealand white rabbit (n=4, weight 3.0 to 3.5 kg, all male) was used for animal model of atherosclerosis. Atherosclerotic aortic lesions were induced by high-cholesterol diet and double balloon injury. T1-weight axial images were acquired before and after gadolinium-based contrast agent using a 3-T MRI. MR images and the matched histopathological sections (n=35) were divided into 4 quadrants or 3 (n=130). Enhancement ratio (ER, ER=SIpost/SIpre) on MRI was calculated for each quadrant and compared with histopathology in regard to lipid-rich and macrophage-rich areas. Results : Lipid-rich quadrants were 72 and fibrous quadrants were 58. The number of quadrants which had macrophage-rich areas was 105 and that of quadrants which did not have macrophage-rich areas was 25. ER was significantly higher in lipid-rich quadrants than in fibrous quadrants (mean ER 2.25c$\pm$0.41 vs. 2.72$\pm$0.65, p=0.013). ER poorly correlated with macrophage-rich areas when lipid-component was controlled (correlation coefficient -0.203, p=0.236). Conclusion : Lipid-rich plaques showed stronger enhancement than fibrous plaques using a standard gadolinium-based extracellular contrast agent. Macrophage infiltration did not correlate with degree of enhancement. Further study is warranted that account for optimal time of imaging after contrast injection using various plaque models from early to advanced stages and all possible parameters associated with contrast enhancement.

• Journal of the HCI Society of Korea
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• v.12 no.4
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• pp.45-55
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• 2017

In recent years, some service providers have introduced chatbot agents to provide engagement in the healthcare field. However, current research on chatbot agents is still limited to designing various chatbot identities for healthcare services. By contrast, this study aims to investigate how various agent identities affect users' perceptions and behaviors differently. We developed three chatbot agents with different identities: a doctor (an individual), a hospital (an institution), and a virtual agent (a machine). Then, we recruited 36 users and divided them into three groups, each using a different chatbot agent. They were asked to track their behaviors and review advice from the chatbot agent for six days. Post-hoc surveys and interviews were conducted in order to investigate users' perceptions. The findings are as follows: participants felt more trusting and intimate with the doctor and hospital agents than with the virtual agent. Many of the participants preferred the hospital agent due to its higher reliability. However, all three agents did not lead the participants to change their behaviors. This study contributes to providing practical guidelines for designing chatbots in the healthcare field by studying users' perceptions and behaviors depending on chatbot identities.

• Journal of the Korean Society of Radiology
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• v.11 no.5
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• pp.329-334
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• 2017

The purpose of this study is to estimating the possibility of manufacturing radiation shielding sheet by searching for environmentally friendly materials suitable for medical environment of medical radiation shielding. There are many tungsten products which are currently used as shielding materials in place of lead, but there are small problems in the mass production of lightweight shielding sheets due to economical efficiency. To solve these problems, a lightweight, environmentally friendly material with economical efficiency is required. In this study, Barium sulphate and Iodine were proposed. Both materials are already used as contrast medias in radiography, and it is predicted that the shielding effect will be sufficient in a certain region as a shielding material because of the characteristic of absorbing radiation. Therefore, in this study, we used a Monte Carlo simulation to simulate radiation shielding materials. When it is a contrast agent such as Barium sulfate and Iodine, the radiation absorption effect in the high energy region appears greatly, and the effectiveness of the two shielding substance in the energy region of the star with thickness of 120 kVp is also evaluated in the medical radiation imaging region. Simulated estimation results it was possible to estimate the effectiveness of shielding for all two substances. Iodine has higher shielding effect than barium sulfate, 0.05 mm thick appears great effect. Therefore, the Monte Carlo simulation confirms that iodine, which is a radiological contrast agent, is also usable as barium sulfate in the production of radiation shielding sheets.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.7
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• pp.4704-4710
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• 2015

The purpose of this study is to obtain a useful diagnostic image by increasing the signal strength of the peripheral artery, was to use a T1 shortening effect of gadolinium contrast agents to improve the disadvantages of the phase image. From october to december 2014 thirty patients were underwent the MRI scanning, except for heart disease. Research method was evaluated comparing the image after gadolinium contrast MR image acquisition step before evaluating the difference between the signal intensity for T1 shortening effect. In frontal lobe 19.45%, temporal lobe 23.09%, occipital lobe 25.45%, parietal lobe 18.82%, cerebellum 20.93% after peripheral arterial signal strength results of gadolinium contrast agent injection was increased significantly after injection of gadolinium both statistically significant. After injecting a contrast agent gadolinium in SWI by increasing the signal strength of the T1 shortening effect can be obtained when using the phase image to give a useful image in diagnosis and treatment.

• Nuclear Medicine and Molecular Imaging
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• v.40 no.3
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• pp.169-176
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• 2006

Purpose: According to the development of CT scanner in PET/CT system, the role of CT unit as a diagnostic tool has been more important. To improve the diagnostic ability of CT scanner, it is a key aspect that CT scanning has to be performed with high dose energy and intravenous (IV) contrast. So we investigated the effect of IV contrast media on the maximum SUV (maxSUV) of normal tissues and pathologic lesions using PET/CT scanner with high dose CT scanning. Materials & Methods: The study enrolled 13 patients who required PET/CT evaluation. At first, the patients were performed whole body non-contrast CT (NCCT-120 kVp, 130 mAs) scan. Then contrast enhanced CT (CECT) scan was performed immediately. Finally PET scan was followed. The PET omission data were reconstructed twice, once with the NCCT and again with the CECT. We measured the maxSUV of 10 different body regions that were considered as normal in ail patients. Also pathologic lesions were investigated. Results: There were not seen focal artifacts in PET images based on CT with IV contrast agent. Firstly, 130 normal regions in 13 patients were evaluated. The maxSUV was significantly different between two PET images (p<0.00)). The maxSUV was $1.1{\pm}0.5$ in PET images with CECT-corrected attenuation and $1.0{\pm}0.5$ in PET images with NCCI-corrected attenuation. The limit of agreement was $0.1{\pm}0.3$ in Bland-Altman analysis. Especially there were significant differences in 6 of 10 regions, apex and base of the right lung, ascending aorta, segment 6 & segment 8 of the liver and spleen (p<0.05). Secondly, 39 pathologic lesions were evaluated. The maxSUV was significantly different between two PET images (p<0.001). The maxSUV was $4.7{\pm}2.0$ in PET images with CECT-corrected attenuation and $4.4{\pm}2.0$ in PET images with NCCT-corrected attenuation. The limit of agreement was $0.4{\pm}0.8$ in Bland-Altman analysis. Conclusion: Although there were increases of maxSUVs in the PET images based on CT with IV contrast agent, it was very narrow in the range of limit of agreement. So there was no significant effect to clinical interpretation for PET images that were corrected attenuation with high dose CT using IV contrast.

• Biomaterials and Biomechanics in Bioengineering
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• v.3 no.3
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• pp.129-140
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• 2016

This article reports the development of biodegradable photoluminescent polymer (BPLP)-based nanoparticles (NPs) incorporating either magnetic nanoparticles (BPLP-MNPs) or gadopentate dimeglumine (BPLP-Gd NPs), for cancer diagnosis and treatment. The aim of the study is to compare these nanoparticles in terms of their surface properties, fluorescence intensities, MR imaging capabilities, and in vitro characteristics to choose the most promising dual-imaging nanoprobe. Results indicate that BPLP-MNPs and BPLP-Gd NPs had a size of $195{\pm}43nm$ and $161{\pm}55nm$, respectively and showed good stability in DI water and 10% serum for 5 days. BPLP-Gd NPs showed similar fluorescence as the original BPLP materials under UV light, whereas BPLP-MNPs showed comparatively less fluorescence. VSM and MRI confirmed that the NPs retained their magnetic properties following encapsulation within BPLP. Further, in vitro studies using HPV-7 immortalized prostate epithelial cells and human dermal fibroblasts (HDFs) showed > 70% cell viability up to $100{\mu}g/ml$ NP concentration. Dose-dependent uptake of both types of NPs by PC3 and LNCaP prostate cancer cells was also observed. Thus, our results indicate that BPLP-Gd NPs would be more appropriate for use as a dual-imaging probe as the contrast agent does not mask the fluorescence of the polymer. Future studies would involve in vivo imaging following administration of BPLP-Gd NPs for biomedical applications including cancer detection.

• Korean Journal of Radiology
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• v.23 no.7
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• pp.697-719
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• 2022

Gadoxetate magnetic resonance imaging (MRI) is widely used in clinical practice for liver imaging. For optimal use, we must understand both its advantages and limitations. This article is the outcome of an online advisory board meeting and subsequent discussions by a multidisciplinary group of experts on liver diseases across the Asia-Pacific region, first held on September 28, 2020. Here, we review the technical considerations for the use of gadoxetate, its current role in the management of patients with hepatocellular carcinoma (HCC), and its relevance in consensus guidelines for HCC imaging diagnosis. In the latter part of this review, we examine recent evidence evaluating the impact of gadoxetate on clinical outcomes on a continuum from diagnosis to treatment decision-making and follow-up. In conclusion, we outline the potential future roles of gadoxetate MRI based on an evolving understanding of the clinical utility of this contrast agent in the management of patients at risk of, or with, HCC.