7 results on '"Thng CH"'
Search Results
2. Correlative assessment of tumor microcirculation using contrast-enhanced perfusion MRI and intravoxel incoherent motion diffusion-weighted MRI: is there a link between them?
- Author
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Bisdas S, Braun C, Skardelly M, Schittenhelm J, Teo TH, Thng CH, Klose U, and Koh TS
- Subjects
- Adult, Aged, Contrast Media, Diffusion, Female, Humans, Image Processing, Computer-Assisted, Male, Microcirculation, Middle Aged, Models, Theoretical, Motion, Organometallic Compounds, Prospective Studies, Software, Diffusion Magnetic Resonance Imaging methods, Glioma blood supply, Magnetic Resonance Angiography methods, Neuroimaging methods, Supratentorial Neoplasms blood supply
- Abstract
The purpose of this study was to correlate intravoxel incoherent motion (IVIM) imaging with classical perfusion-weighted MRI metrics in human gliomas. Parametric images for slow diffusion coefficient (D), fast diffusion coefficient (D*), and fractional perfusion-related volume (f) in patients with high-grade gliomas were generated. Maps of Fp (plasma flow), vp (vascular plasma volume), PS (permeability surface-area product), ve (extravascular, extracellular volume), E (extraction ratio), ke (influx ratio into the interstitium), and tc (vascular transit time) from dynamic contrast-enhanced (DCE) and dynamic susceptibility contrast-enhanced (DSC) MRI were also generated. A region-of-interest analysis on the contralateral healthy white matter and on the tumor areas was performed and the extracted parameter values were tested for any significant differences among tumor grades or any correlations. Only f could be significantly correlated to DSC-derived vp and tc in healthy brain tissue. Concerning the tumor regions, Fp was significantly positively correlated with D* and inversely correlated with f in DSC measurements. The D*, f, and f × D* values in the WHO grade III gliomas were non-significantly different from those in the grade IV gliomas. There was a trend to significant negative correlations between f and PS as well as between f × D* and ke in DCE experiments. Presumably due to different theoretical background, tracer properties and modeling of the tumor vasculature in the IVIM theory, there is no clearly evident link between D*, f and DSC- and DCE-derived metrics., (Copyright © 2014 John Wiley & Sons, Ltd.)
- Published
- 2014
- Full Text
- View/download PDF
3. Assessment of tumor necrotic fraction by dynamic contrast-enhanced MRI: a preclinical study of human tumor xenografts with histopathologic correlation.
- Author
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Koh TS, Thng CH, Hartono S, Dominguez LT, Lim TK, Huynh H, Martarello L, and Ng QS
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- Animals, Humans, Male, Mice, Mice, SCID, Necrosis, Neoplasms pathology, Staining and Labeling, Contrast Media, Magnetic Resonance Imaging, Neoplasms diagnosis, Xenograft Model Antitumor Assays
- Abstract
Contrary to the common notion that tumor necrotic regions are non-enhancing after contrast administration, recent evidence has shown that necrotic regions exhibit delayed and slow uptake of gadolinium tracer on dynamic contrast-enhanced MRI (DCE MRI). The purpose of this study is to explore whether the mapping of tumor voxels with delayed and slow enhancement on DCE MRI can be used to derive estimates of tumor necrotic fraction. Patient-derived tumor xenograft lines of seven human cancers were implanted in 26 mice which were subjected to DCE MRI performed using a spoiled gradient recalled sequence. Gadolinium tracer concentration was estimated using the variable flip angle technique. To identify tumor voxels exhibiting delayed and slow uptake of contrast medium, clustering analysis was performed using a k-means clustering algorithm that classified tumor voxels according to their contrast enhancement patterns. Comparison of the percentage of tumor voxels exhibiting delayed and slow enhancement with the tumor necrotic fraction estimated on histology showed a strong correlation (r = 0.962, p < 0.001). The mapping of tumor regions with delayed and slow contrast uptake on DCE MRI correlated strongly with tumor necrotic fraction, and can potentially serve as a non-invasive imaging surrogate for the in vivo assessment of necrotic fraction., (Copyright © 2014 John Wiley & Sons, Ltd.)
- Published
- 2014
- Full Text
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4. In vivo measurement of gadolinium diffusivity by dynamic contrast-enhanced MRI: a preclinical study of human xenografts.
- Author
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Koh TS, Hartono S, Thng CH, Lim TK, Martarello L, and Ng QS
- Subjects
- Animals, Cell Line, Tumor, Diffusion, Humans, Male, Mice, Mice, Inbred C57BL, Contrast Media pharmacokinetics, Gadolinium DTPA, Liver Neoplasms, Experimental pathology, Magnetic Resonance Imaging methods, Neoplasm Transplantation
- Abstract
Compartmental tracer kinetic models currently used for analysis of dynamic contrast-enhanced MRI data yield poor fittings or parameter values that are unphysiological in necrotic regions of the tumor, as these models only describe microcirculation in perfused tissue. In this study, we explore the use of Fick's law of diffusion as an alternative method for analysis of dynamic contrast-enhanced MRI data in the necrotic regions. Xenografts of various human cancer cell lines were implanted in 14 mice that were subjected to dynamic contrast-enhanced MRI performed using a spoiled gradient recalled sequence. Tracer concentration was estimated using the variable flip angle technique. Poorly perfused and necrotic tumor regions exhibiting delayed and slow enhancement were identified using a k-means clustering algorithm. Tracer behavior in necrotic regions was shown to be consistent with Fick's diffusion equation and the in vivo gadolinium diffusivity was estimated to be 2.08 (±0.88) × 10(-4) mm(2)/s. This study proposes the use of gadolinium diffusivity as an alternative parameter for quantifying tracer transport within necrotic tumor regions., (Copyright © 2012 Wiley Periodicals, Inc.)
- Published
- 2013
- Full Text
- View/download PDF
5. A comparative study of dynamic contrast-enhanced MRI parameters as biomarkers for anti-angiogenic drug therapy.
- Author
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Koh TS, Thng CH, Hartono S, Tai BC, Rumpel H, Ong AB, Sukri N, Soo RA, Wong CI, Low AS, Humerickhouse RA, and Goh BC
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- Adult, Aged, Angiogenesis Inhibitors blood, Area Under Curve, Demography, Disease Progression, Female, Humans, Kaplan-Meier Estimate, Male, Middle Aged, Neovascularization, Pathologic blood, Statistics, Nonparametric, Time Factors, Angiogenesis Inhibitors therapeutic use, Biomarkers, Tumor metabolism, Indazoles therapeutic use, Magnetic Resonance Imaging methods, Neovascularization, Pathologic drug therapy, Phenylurea Compounds therapeutic use
- Abstract
The aim of the present study was to compare three tracer kinetics methods for the analysis of dynamic contrast-enhanced (DCE) MRI data, namely the generalized kinetics model, the distributed-parameter model and the initial area under the tumor tracer curve (IAUC) method, in a Phase I study of an anti-angiogenic drug ABT -869; and to explore their utility as biomarkers. Twenty-eight patients with a range of tumors formed the study population. DCE MRI performed at baseline and 2 weeks post-treatment was analyzed using all three methods, yielding percentage changes for various tracer kinetics parameters. Correlation analyzes were performed between these parameters and in relation to drug exposure. The association of these parameters with time-to-progression was examined using receiver-operating characteristic and Kaplan-Meier curves. Significant correlation with drug exposure was found for the following parameters: normalized IAUC (IAUC(norm)), fractional interstitial volume v(e), fractional intravascular volume v(1) and permeability PS. However, only v(e) and PS were effective in predicting late progression. A decrease in v(e) of more than 1.7% and a decrease in PS of more than 25.1% observed at 2 weeks post-treatment could be associated with late progression. All three tracer kinetics methods have biomarker potential for assessing the effects of anti-angiogenic therapy., (Copyright © 2011 John Wiley & Sons, Ltd.)
- Published
- 2011
- Full Text
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6. Dynamic contrast-enhanced MRI of neuroendocrine hepatic metastases: A feasibility study using a dual-input two-compartment model.
- Author
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Koh TS, Thng CH, Hartono S, Kwek JW, Khoo JB, Miyazaki K, Collins DJ, Orton MR, Leach MO, Lewington V, and Koh DM
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- Computer Simulation, Contrast Media, Feasibility Studies, Humans, Image Enhancement methods, Liver Neoplasms metabolism, Models, Biological, Neuroendocrine Tumors metabolism, Reproducibility of Results, Sensitivity and Specificity, Gadolinium DTPA pharmacokinetics, Image Interpretation, Computer-Assisted methods, Liver Neoplasms diagnosis, Liver Neoplasms secondary, Magnetic Resonance Imaging methods, Neuroendocrine Tumors diagnosis, Neuroendocrine Tumors secondary
- Abstract
Neuroendocrine hepatic metastases exhibit various contrast uptake enhancement patterns in dynamic contrast-enhanced MRI. Using a dual-input two-compartment distributed parameter model, we analyzed the dynamic contrast-enhanced MRI datasets of seven patient study cases with the aim to relate the tumor contrast uptake patterns to parameters of tumor microvasculature. Simulation studies were also performed to provide further insights into the effects of individual microcirculatory parameter on the tumor concentration-time curves. Although the tumor contrast uptake patterns can be influenced by many parameters, initial results indicate that hepatic blood flow and the ratio of fractional vascular volume to fractional interstitial volume may potentially distinguish between the patterns of neuroendocrine hepatic metastases., (© 2010 Wiley-Liss, Inc.)
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- 2011
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7. Paclitaxel, carboplatin, and gemcitabine in metastatic nasopharyngeal carcinoma: a Phase II trial using a triplet combination.
- Author
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Leong SS, Wee J, Tay MH, Toh CK, Tan SB, Thng CH, Foo KF, Lim WT, Tan T, and Tan EH
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- Adult, Aged, Antineoplastic Combined Chemotherapy Protocols adverse effects, Carboplatin administration & dosage, Carcinoma pathology, Deoxycytidine administration & dosage, Disease-Free Survival, Drug Administration Schedule, Female, Humans, Male, Middle Aged, Nasopharyngeal Neoplasms pathology, Neutropenia chemically induced, Paclitaxel administration & dosage, Severity of Illness Index, Survival Analysis, Thrombocytopenia chemically induced, Treatment Outcome, Gemcitabine, Antineoplastic Combined Chemotherapy Protocols therapeutic use, Carcinoma drug therapy, Deoxycytidine analogs & derivatives, Nasopharyngeal Neoplasms drug therapy
- Abstract
Background: Patients with nasopharyngeal carcinoma (NPC) are treated primarily with radiotherapy. In the disseminated state, platinum-based, 2-drug combination regimens yielded response rates of 55-75%, achieving a median survival of 10-12 months. With the proven efficacy of second-generation cytotoxics like paclitaxel and gemcitabine in patients with metastatic NPC, the authors hypothesized that a triplet combination incorporating these newer cytotoxics may improve treatment results., Methods: Thirty-two patients with metastatic NPC were treated with combination chemotherapy that included paclitaxel 70 mg/m(2) on Days 1 and 8, carboplatin dosed to area under curve of 5 on Day 1, and gemcitabine 1000 mg/m(2) on Days 1 and 8 every 21 days for a maximum of 8 cycles., Results: Two patients achieved a complete response, and 23 patients achieved a partial response, for an overall response rate of 78%. The main toxicities were hematologic, with 41% of patients experiencing Grade 3 or 4 anemia, 41% of patients experiencing Grade 3 or 4 thrombocytopenia, and 78% of patients experiencing Grade 3 or 4 neutropenia. The median time to disease progression was 8.1 months, and the median overall survival was 18.6 months., Conclusions: The combination of paclitaxel, carboplatin, and gemcitabine showed promising efficacy against metastatic NPC but at the expense of considerable toxicity., ((c) 2004 American Cancer Society)
- Published
- 2005
- Full Text
- View/download PDF
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