Browsing by Author "Chiu, Yen-Yu"

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Comparison of Gd-Bz-TTDA, Gd-EOB-DTPA, and Gd-BOPTA for dynamic MR imaging of the liver in rat models
(2012-03-01)
Jaw, Twei-Shiun
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Chen, Shih-Hsien
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Wang, Yun-Ming
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Hsu, Jui-Sheng
;
Kuo, Yu-Ting
To evaluate the competitive potential of a new lipophilic paramagnetic complex, Gd-Bz-TTDA [4-benzyl-3,6,10-tri (carboxymethyl)-3,6,10-triazado-decanedioic acid] compared with two other commercially available MR hepatobiliary contrast agents, gadobenate dimeglumine (Gd-BOPTA) and gadoxetic acid (Gd-EOB-DTPA), dynamic MR imaging studies were performed on normal and hepatocellular carcinoma (HCC) rat models using a 1.5-Tesla MR scanner. The results indicate that normal rats that were injected with 0.1 mmol/kg Gd-Bz-TTDA showed significantly more intense and persistent liver enhancement than those that were injected with the same dose of Gd-EOB-DTPA or Gd-BOPTA. All of these agents showed similar enhancement patterns in the implanted HCC. The liver-lesion contrast-to-noise ratios were higher and more persistent in rats that were injected with Gd-Bz-TTDA. These results indicate that Gd-Bz-TTDA is comparable with the commercially available hepatobiliary agents, Gd-EOB-DTPA and Gd-BOPTA, and can result in more intense and prolonged liver enhancement while still providing better liver-lesion discrimination. These results warrant further large-scale studies. Copyright (C) 2012, Elsevier Taiwan LLC. All rights reserved.
Development of a Gd(III)-Based Receptor-Induced Magnetization Enhancement (RIME) Contrast Agent for beta-Glucuronidase Activity Profiling
(2012-11-19)
Chen, Shih-Hsien
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Kuo, Yu-Ting
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Singh, Gyan
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Cheng, Tian-Lu
;
Su, Yu-Zheng
beta-Glucuronidase is a key lysosomal enzyme and is often overexpressed in necrotic tumor masses. We report here the synthesis of a pro receptor induced magnetization enhancement (pro RIME) magnetic resonance imaging (MRI) contrast agent ([Gd(DOTA-FP beta Gu)]) for molecular imaging of beta-glucuronidase activity in tumor tissues. The contrast agent consists of two parts, a gadolinium complex and a beta-glucuronidase substrate (beta-D-glucopyranuronic acid). The binding association constant (K-A) of [Gd(DOTA-FP beta Gu)] is 7.42 X 10(2), which is significantly lower than that of a commercially available MS-325 (K-A = 3.0 x 10(4)) RIME contrast agent. The low K-A value of [Gd(DOTA-FP beta Gu)] is due to the pendant beta-D-glucopyranuronic acid moiety. Therefore, [Gd(DOTA-FP beta Gu)] can be used for detection of beta-glucuronidase through RIME modulation. The detail mechanism of enzymatic activation of [Gd(DOTA-FP beta Gu)] was elucidated by LC-MS. The kinetics of beta-glucuronidase catalyzed hydrolysis of [Eu(DOTA-FP beta Gu)] at pH 7.4 best fit the Miechalis-Menten kinetic mode with K-m = 1.38 mM, K-cat = 3.76 x 10(3), and k(cat)/K-m = 2.72 x 10(3) M-1 s(-1). The low K-m value indicates high affinity of beta-glucuronidase for [Gd(DOTA-FP beta Gu)] FP beta Gu) at physiological pH. Relaxometric studies revealed that T-1 relaxivity of [Gd(DOTA-FP beta Gu)] changes in response to the concentration of beta-glucuronidase. Consistent with the relaxometric studies, [Gd(DOTA-FP beta Gu)] showed significant change in MR image signal in the presence of beta-glucuronidase and HSA. In vitro and in vivo MR images demonstrated appreciable differences in signal enhancement in the cell lines and tumor xenografts in accordance to their expression levels of beta-glucuronidase. [GRAPHICS] .
Effect of Rainfall, Runoff and Infiltration Processes on the Stability of Footslopes
(2020-05-01)
Chen, Hung-En
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Chiu, Yen-Yu
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Tsai, Tung-Lin
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Yang, Jinn-Chuang
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防災與水環境研究中心
To analyze the effect of runoff on shallow landslides, a model coupling one-dimensional rainfall-runoff and two-dimensional infiltration was established to simulate rainfall, infiltration, and runoff processes. Based on Bishop's limit equilibrium method, the slope failure of a hypothetical footslope was studied. First, conditions with and without inflow were compared. The results reveal a remarkable difference in factors of safety (FS) between the two conditions, suggesting that considering the effect of runoff is crucial for landslide modeling. In terms of a series of tests of the various magnitudes, durations, lag-time, and peak position of the hydrograph, analyses show that larger inflow leads to more accumulated infiltration and triggers landslides earlier. A long-term duration inflow decreases the stability more than short intensive inflow does. With subsequent surface inflow, slope failure may occur after rainfalls stop, owing to the inflow, and the shape of inflow hydrographs could slightly affect the variance in FS. Results also indicate the necessity of considering the surface runoff when using a numerical model to analyze landslide, particularly on a footslope.
In vivo magnetic resonance imaging of mice liver tumors using a new gadolinium-based contrast agent
(2013-05-01)
Chen, Shih-Hsien
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Kuo, Yu-Ting
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Cheng, Tian-Lu
;
Chen, Chiao-Yun
;
Chiu, Yen-Yu
We compared the enhancement effect between a newly synthesized tissue-specific contrast agent, [Gd-DOTA-FP beta G], and a commercially available agent, [Gd(DOTA)](-), in a murine model of liver tumor using a clinical magnetic resonance imaging scanner. The colon cancer cell lines with and without beta-glucuronidase (beta G) expression were implanted into the liver of mice. Self-synthesized gadolinium-based magnetic resonance contrast agent, [Gd(DOTA-FP beta G)], was administered to measure enhancement on magnetic resonance images using a commercially available agent, [Gd(DOTA)](-), as control in a clinical 3.0 tesla (T) magnetic resonance scanner. In vivo fluorescence imaging and histopathology of the liver were also performed to compare and correlate with the magnetic resonance studies. The in vivo fluorescence imaging failed to depict a sufficiently intense signal for liver or liver tumor of mice without exposure of the liver following an incision on the abdominal wall. The tissue-specific magnetic resonance agent, [Gd(DOTA-FP beta G)], caused significantly stronger enhancement in tumors expressing beta G (CT26/m beta G-eB7) than in tumors not expressing beta G (CT26) (p < 0.05). In the magnetic resonance imaging studies using control agent [Gd(DOTA)](-), the tumors with and without beta G expression depicted no significant difference in enhancement on the T1-weighted images. The [Gd(DOTA-FP beta G)] also provided significantly more contrast uptake in the CT26/m beta G-eB7 tumor than in the normal liver parenchyma, whereas the [Gd(DOTA)](-) did not. This study confirms that better contrast enhancement can be readily detected in vivo by the use of a tissue-specific magnetic resonance contrast agent to target tumor cells with specific biomarkers in a clinical magnetic resonance imaging scanner. Copyright (c) 2012, Kaohsiung Medical University. Published by Elsevier Taiwan LLC. All rights reserved.
Investigation of the Influence of Rainfall Runoff on Shallow Landslides in Unsaturated Soil Using a Mathematical Model
(2019-06-01)
Chiu, Yen-Yu
;
Chen, Hung-En
;
Yeh, Keh-Chia
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土木工程學系
;
Department of Civil Engineering
Infiltration and groundwater have been widely considered as the main factors that cause shallow landslides; however, the effect of runoff has received less attention. In this study, an in-house physical-process-based shallow landslide model is developed to demonstrate the influence of runoff. The model is controlled by coupling the shallow water equation (dynamic) and Richards' equation. An infinite slope stability analysis is applied to evaluate the possibility of regional landslides. A real, small catchment topography is adopted as a demonstration example. The simulation illustrates the variations of runoff and the factor of safety (FS) during a storm. The results indicate that, after the surface becomes saturated, the FS may keep varying due to the increasing pressure head, which is caused by increasing surface water depth. This phenomenon most likely occurs downstream where the slopes easily accumulate water. The depth of the surface water may also be a factor of slope failure. Therefore, it is essential to increase the accuracy of calculating the runoff depth when assessing regional shallow landslides.