Chao-Ying Wang

National Taiwan University, Taipei, Taipei, Taiwan

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Publications (9)35.09 Total impact

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    ABSTRACT: BACKGROUND AND PURPOSE: Brain enhancement on contrast-enhanced T1-weighted imaging (CET1-WI) after ischemic stroke is generally accepted as an indicator of the blood-brain barrier disruption. However, this phenomenon usually starts to become visible at the subacute phase. The purpose of this study was to evaluate the time-course profiles of K(trans), cerebral blood volume (vp), and CET1-WI with early detection of blood-brain barrier changes on K(trans) maps and their role for prediction of subsequent hemorrhagic transformation in acute middle cerebral arterial infarct. METHODS: Twenty-six patients with acute middle cerebral arterial stroke and early spontaneous reperfusion, whose MR images were obtained at predetermined stroke stages, were included. T2*-based MR perfusion-weighted images were acquired using the first-pass pharmacokinetic model to derive K(trans) and vp. Parenchymal enhancement observed on maps of K(trans), vp, and CET1-WI at each stage was compared. Association among these measurements and hemorrhagic transformation was analyzed. RESULTS: K(trans) map showed significantly higher parenchymal enhancement in ischemic parenchyma as compared with that of vp map and CET1-WI at early stroke stages (P<0.05). The increased K(trans) at acute stage was not associated with parenchymal enhancement in CET1-WI at the same stage. Parenchymal enhancement in CET1-WI started to occur at the late subacute stage and tended to be luxury reperfusion-dependent. Patients with hemorrhagic transformation showed higher mean K(trans) values as compared with patients without hemorrhagic transformation (P=0.02). CONCLUSIONS: Postischemic brain enhancement on routine CET1-WI seems to be closely related to the luxury reperfusion at the late subacute stage and is not dependent on microvascular permeability changes at the acute stage.
    Stroke 06/2013; · 6.16 Impact Factor
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    ABSTRACT: The magnetic resonance (MR) T2 value of cartilage is a reliable indicator of tissue properties and therefore may be used as an objective diagnostic tool in early meniscal degeneration. The purpose of this study was to investigate age, gender, location, and zonal differences in MR T2 value of the posterior horns of knee menisci in asymptomatic subjects. Sixty asymptomatic volunteers (30 men and 30 women) were enrolled and divided into three different age groups: 20-34, 35-49 and 50-70 years. The inclusion criteria were BMI<30 kg/cm(2) , normalized Western Ontario and McMaster Universities (WOMAC) pain score of zero, and no evidence of meniscal and ligamentous abnormalities on routine knee MR imaging. The T2 values were measured on images acquired with a T2-weighted fat-suppressed turbo spin-echo sequence at 3T. The mean T2 values in both medial and lateral menisci for the 20-34, 35-49, and 50-70 age groups were 9.94 msec±0.94, 10.73 msec±1.55, and 12.36 msec±2.27, respectively, for women and 9.17 msec±0.74, 9.64 msec±0.67, and 10.95 msec±1.33, respectively, for men. The T2 values were significantly higher in the 50-70 age group than the 20-34 age group (P<0.001) and in women than in men (P = 0.001, 0.004, and 0.049 for each respective age group). T2 values were significantly higher in medial menisci than in lateral menisci only in women age 50-70 (3.33 msec, P = 0.006) and in the white zone and red/white zone of the 50-70 and 35-49 age groups than that of the 20-34 age group (2.47, 1.02; 2.77, 1.16 msec, respectively, all P<0.01). The MR T2 values of the posterior meniscal horns increase with increasing age in women and are higher in women than in men. The age-related rise of T2 values appears to be more severe in medial menisci than in lateral menisci. Differences exist in the white zone and red/white zone.
    PLoS ONE 01/2013; 8(3):e59769. · 3.53 Impact Factor
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    ABSTRACT: To investigate the effects of 3,4-methylenedioxymethamphetamine (MDMA, commonly known as "ecstasy") on the alterations of brain metabolites and anatomic tissue integrity related to the function of the basal ganglia-thalamocortical circuit by using proton magnetic resonance (MR) spectroscopy and diffusion-tensor MR imaging. This study was approved by a local institutional review board, and written informed consent was obtained from all subjects. Thirty-one long-term (>1 year) MDMA users and 33 healthy subjects were enrolled. Proton MR spectroscopy from the middle frontal cortex and bilateral basal ganglia and whole-brain diffusion-tensor MR imaging were performed with a 3.0-T system. Absolute concentrations of metabolites were computed, and diffusion-tensor data were registered to the International Consortium for Brain Mapping template to facilitate voxel-based group comparison. The mean myo-inositol level in the basal ganglia of MDMA users (left: 4.55 mmol/L ± 2.01 [standard deviation], right: 4.48 mmol/L ± 1.33) was significantly higher than that in control subjects (left: 3.25 mmol/L ± 1.30, right: 3.31 mmol/L ± 1.19) (P < .001). Cumulative lifetime MDMA dose showed a positive correlation with the levels of choline-containing compounds (Cho) in the right basal ganglia (r = 0.47, P = .02). MDMA users also showed a significant increase in fractional anisotropy (FA) in the bilateral thalami and significant changes in water diffusion in several regions related to the basal ganglia-thalamocortical circuit as compared with control subjects (P < .05; cluster size, >50 voxels). Increased myo-inositol and Cho concentrations in the basal ganglia of MDMA users are suggestive of glial response to degenerating serotonergic functions. The abnormal metabolic changes in the basal ganglia may consequently affect the inhibitory effect of the basal ganglia to the thalamus, as suggested by the increased FA in the thalamus and abnormal changes in water diffusion in the corresponding basal ganglia-thalamocortical circuit.
    Radiology 06/2011; 260(2):531-40. · 6.34 Impact Factor
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    ABSTRACT: To investigate quantitatively the topographic perfusion characteristics of the adenohypophysis by using dynamic contrast material-enhanced magnetic resonance (MR) imaging in a subgroup of patients with idiopathic growth hormone deficiency (IGHD) and with normal-appearing pituitary morphology on MR images. This HIPAA-compliant, prospective study was approved by an institutional review board, and informed consent was obtained for all patients. Twenty-five patients (mean age, 10.6 years ± 3.3 [standard deviation]) with clinical growth retardation, proved IGHD, and normal pituitary morphology on MR images were included for analysis. Sixteen children (mean age, 10.8 years ± 5.5) were included as control subjects. Time to peak (TTP) perfusion properties of the adenohypophysis in 10 regions of interest from multisection coronal dynamic contrast-enhanced T1-weighted MR images were quantitatively derived by using the Brix pharmacokinetic model. Significant difference was determined with a two-tailed Student t test. The Pearson correlation coefficient was used to correlate the perfusion parameters, including maximal enhancement peak and slope, with serum growth hormone levels in the IGHD group. TTP for the IGHD group was significantly prolonged compared with that for the control group (P < .005). The prolonged TTP in the IGHD group was found to be diffuse. The levels of growth hormone deficiency were negatively correlated with the peak enhancement and the slope of the wash-in phase, which suggests increased blood volume in IGHD within the pituitary gland. IGHD and the degree of growth hormone deficiency are associated with nonregional perfusion delay in morphologically normal adenohypophyses. The lack of lateralization of perfusion delay may suggest that microvascular structural abnormalities play a role in IGHD.
    Radiology 09/2010; 258(1):213-21. · 6.34 Impact Factor
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    ABSTRACT: Although isotropic diffusion-weighted imaging (isoDWI) is very sensitive to the detection of acute ischemic stroke, it may occasionally show diffusion negative result in hyper-acute stroke. We hypothesize that high diffusion contrast diffusion trace-weighted image with enhanced T2 may improve stroke lesion conspicuity. Five hyper acute stroke patients (M:F=0:5, average age=61.8+/-20.5 y/o) and 16 acute stroke patients (M:F=11:5, average age=67.7+/-12 y/o) were examined six-direction tensor DWIs at b=707s/mm(2). Three different diffusion-weighted images, including isotropic (isoDWI), diffusion trace-weighted image (trDWI) and T2-enhanced diffusion trace-weighted image (T2E_trDWI), were generated. Normalized lesion-to-normal ratio (nLNR) and contrast-to-noise ratio (CNR) of three diffusion images were calculated from each patient and statistically compared. The trDWI shows better nLNR than isoDWI on both hyper-acute and acute stroke lesions, whereas no significant improvement in CNR. Nevertheless, the T2E_trDWI has statistically superior CNR and nLNR than those of isoDWI and trDWI in both hyper-acute and acute stroke. We concluded that tensor diffusion trace-weighted image with T2 enhancement is more sensitive to stroke lesion detection, and can provide higher lesion conspicuity than the conventional isotropic DWI for early stroke lesion delineation without the need of high-b-value technique.
    European journal of radiology 06/2009; 74(3):e89-94. · 2.65 Impact Factor
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    ABSTRACT: We aimed to quantitatively investigate the alteration of parotid perfusion after irradiation using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) based on a two-compartment tracer kinetic model. This study enrolled 19 patients (53.2 +/- 14.9 years) treated by head and neck radiotherapy and 19 age-relevant and sex-matched subjects as a control group. Perfusion parameters (K ( el ), k (21) and A) of parotid glands were analyzed based on the Brix model from T1-weighted DCE-MRI. Suitability of the Brix model was evaluated via Monte Carlo simulation for the goodness-of-fit. Analysis of nonlinear goodness-of-fit showed that the Brix model is appropriate in evaluating the parotid perfusion (R(2) = 0.938 +/- 0.050). The irradiated parotid glands showed significantly lower K ( el ) (P < 0.0005) and k (21) (P < 0.05) and consequently significantly higher value of peak enhancement (P < 0.0005) and time-to-peak (P < 0.0005) compared with non-irradiated ones, suggestive of gradual and prolonged accumulation and delayed wash-out of contrast agent due to increased extracellular extravascular space and decreased vascular permeability in the irradiated glands. Linear regression analysis showed dose-dependent perfusion changes of the irradiated parotid glands. We conclude that quantitative DCE-MRI is a potential tool in investigating parotid gland perfusion changes after radiotherapy.
    European Radiology 01/2009; 19(1):94-102. · 4.34 Impact Factor
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    ABSTRACT: To develop an adaptive subvoxel stepping scheme, as an adjunct to tensor deflection (TEND) tractography, that automatically adjusts the stepping size by considering the tensor linearity to properly trace fiber bundles in regions with different degrees of tensor anisotropy. A theoretical investigation of the TEND algorithm was performed to assess the degree of deflection of the propagation vector toward the major eigenvector. Mathematically generated phantoms (one with curved fibers and the other with crossing fibers) at wide ranges of signal-to-noise ratio (SNR), and human brain images obtained in vivo were used to test the performance of the adaptive stepping algorithm. The degree of deflection was found to be inversely related to the stepping size. A small stepping size was advantageous for tracing single curved fiber bundles, whereas a large stepping size was beneficial for passing through fiber crossing regions. The performance of the adaptive stepping algorithm was superior to fixed stepping in both situations, leading to an approximately 0.17 voxel of deviation in curved fibers and a nearly 100% successful tracking rate in crossing fibers at typical SNR. Human brain images demonstrated similar results. The adaptive stepping algorithm is a helpful adjunct to TEND tractography.
    Journal of Magnetic Resonance Imaging 09/2006; 24(2):451-8. · 2.57 Impact Factor
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    ABSTRACT: Partial volume with CSF is known to contaminate the quantification of white matter anisotropy depicted by diffusion tensor imaging (DTI). We hypothesized that the FLAIR technique helps to improve DTI white matter tractography in the normal adult brain by eliminating CSF partial volume effects. Seven healthy adults aged 23-37 underwent both conventional and FLAIR DTI at 1.5T. Each subject was imaged five times. Neural fiber tractography was performed with both sequences by using two algorithms: a voxel-based method (EZ-tracing) with global seed points and another based on subvoxel tractography (tensor deflection) by using manual encircling of local seed points. Total volume of the fibers tracked was compared for the two types of images. Fiber tracking was substantially most successful on FLAIR DTI near the lateral ventricles and the sulci, where CSF partial volume effects were likely present. Minor false tracts on FLAIR images, possibly due to a reduced signal-to-noise ratio, were found in regions relatively free of CSF contamination; however, they did not affect tracking of major periventricular white matter bundles, such as those related to the corpus callosum or the corona radiata. When we excluded false tracts, the FLAIR technique depicted an average of 17% more fibers in volume than conventional DTI in the periventricular regions (P < .0005, paired Student t test). Despite the reduction of signal-to-noise ratio and longer imaging times, FLAIR improved tractography by eliminating CSF partial volume effects.
    American Journal of Neuroradiology 03/2005; 26(3):591-7. · 3.17 Impact Factor
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    Chang-Shin Lee, Cheng-Yu Chen, Chao-Ying Wang

Publication Stats

57 Citations
35.09 Total Impact Points

Institutions

  • 2005–2010
    • National Taiwan University
      • Department of Electrical Engineering
      Taipei, Taipei, Taiwan
  • 2009
    • Tri-Service General Hospital
      T’ai-pei, Taipei, Taiwan