Chun-Sing Wong

The University of Hong Kong, Hong Kong, Hong Kong

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Publications (15)51.16 Total impact

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    ABSTRACT: Diffusion tensor imaging has already been extensively used to probe microstructural alterations in white matter tracts, and scarcely, in deep gray matter. However, results in literature regarding age-related degenerative mechanisms in white matter tracts and parametric changes in the putamen are inconsistent. Diffusional kurtosis imaging is a mathematical extension of diffusion tensor imaging, which could more comprehensively mirror microstructure, particularly in isotropic tissues such as gray matter. In this study, we used the diffusional kurtosis imaging method and a white-matter model that provided metrics of explicit neurobiological interpretations in healthy participants (58 in total, aged from 25 to 84 years). Tract-based whole-brain analyses and regions-of-interest (anterior and posterior limbs of the internal capsule, cerebral peduncle, fornix, genu and splenium of corpus callosum, globus pallidus, substantia nigra, red nucleus, putamen, caudate nucleus, and thalamus) analyses were performed to examine parametric differences across regions and correlations with age. In white matter tracts, evidence was found supportive for anterior-posterior gradient and not completely supportive for retrogenesis theory. Age-related degenerations appeared to be broadly driven by axonal loss. Demyelination may also be a major driving mechanism, although confined to the anterior brain. In terms of deep gray matter, higher mean kurtosis and fractional anisotropy in the globus pallidus, substantia nigra, and red nucleus reflected higher microstructural complexity and directionality compared with the putamen, caudate nucleus, and thalamus. In particular, the unique age-related positive correlations for fractional anisotropy, mean kurtosis, and radial kurtosis in the putamen opposite to those in other regions call for further investigation of exact underlying mechanisms. In summary, the results suggested that diffusional kurtosis can provide measurements in a new dimension that were complementary to diffusivity metrics. Kurtosis together with diffusivity can more comprehensively characterize microstructural compositions and age-related changes than diffusivity alone. Combined with proper model, it may also assist in providing neurobiological interpretations of the identified alterations.
    Neurobiology of aging. 04/2014;
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    ABSTRACT: PURPOSE Newly introduced method of diffusional kurtosis imaging (DKI) is able to delineate non-Gaussian diffusion, which is beyond the scope of conventional diffusion tensor imaging (DTI). Clarifying whether the more accurate approach can improve imaging diagnosis of Alzheimer’s disease (AD) is of intense interests. METHOD AND MATERIALS DKI data were collected from a 3T scanner with 3 b values (0, 1000, 2000 s/mm2) and 32 diffusion directions. Using SPM, we conducted two sample t-test of DKI parametric maps voxel-by-voxel between two groups of 11 ADs, 20 normal controls (NCs). Statistical maps were thresholded at p < 0.001 and clusters with at least 500 edge-connected voxels were labeled. RESULTS In AD patients, compared with NC, significantly lower fractional anisotropy were observed in right frontal cortex and gyrus, right temporal cortex and gyrus. In addition, significantly higher mean diffusivity were observed in right temporal white matter, and significantly lower mean kurtosis in right inferior frontal gyrus, left and right temporal cortex, left and right inferior longitudinal fasciculus. CONCLUSION Adding to the traditional DTI metrics, DKI metric like mean kurtosis can provide new regional contrast between AD and NC. CLINICAL RELEVANCE/APPLICATION Therefore, DKI may potentially improve detection of early disease.
    Radiological Society of North America 2013 Scientific Assembly and Annual Meeting; 12/2013
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    ABSTRACT: To improve the accuracy of volume and apparent diffusion coefficient (ADC) measurements in diffusion-weighted magnetic resonance imaging (MRI), we proposed a method based on thresholding both the b0 images and the ADC maps. In 21 heterogeneous lesions from patients with metastatic gastrointestinal stromal tumors (GIST), gross lesion were manually contoured, and corresponding volumes and ADCs were denoted as gross tumor volume (GTV) and gross ADC (ADCg), respectively. Using a k-means clustering algorithm, the probable high-cellularity tumor tissues were selected based on b0 images and ADC maps. ADC and volume of the tissues selected using the proposed method were denoted as thresholded ADC (ADCthr) and high-cellularity tumor volume (HCTV), respectively. The metabolic tumor volume (MTV) in positron emission tomography (PET)/computed tomography (CT) was measured using 40% maximum standard uptake value (SUVmax) as the lower threshold, and corresponding mean SUV (SUVmean) was also measured. HCTV had excellent concordance with MTV according to Pearson's correlation (r=0.984, P<.001) and linear regression (slope = 1.085, intercept = -4.731). In contrast, GTV overestimated the volume and differed significantly from MTV (P=.005). ADCthr correlated significantly and strongly with SUVmean (r=-0.807, P<.001) and SUVmax (r=-0.843, P<.001); both were stronger than those of ADCg. The proposed lesion-adaptive semiautomatic method can help segment high-cellularity tissues that match hypermetabolic tissues in PET/CT and enables more accurate volume and ADC delineation on diffusion-weighted MR images of GIST.
    International journal of radiation oncology, biology, physics 10/2013; 87(2):407-13. · 4.59 Impact Factor
  • Annals of Hematology 08/2013; · 2.87 Impact Factor
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    ABSTRACT: OBJECTIVES: To evaluate dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) for characterising nasopharyngeal carcinoma (NPC). METHODS: Forty-five newly diagnosed NPC patients were recruited. The initial enhancement rate (E ( R )), contrast transfer rate (k ( ep )), elimination rate (k ( el )), maximal enhancement (MaxEn) and initial area under the curve (iAUC) were calculated from semiquantitative analysis. The K ( trans ) (volume transfer constant), v ( e ) (volume fraction) and k ( ep ) were calculated from quantitative analysis. Student's t-test was used to evaluate the differences among tumour stages. Pearson's correlation between the two sets of k ( ep ) was performed. RESULTS: Comparing tumours of T1/2 stage (n = 18) and T3/4 stage (n = 27), MaxEn (P = 0.030) and iAUC (P = 0.039) were both significantly different; however, the iAUC was the only independent variable with 69.6 % sensitivity and 76.5 % specificity respectively; v ( e ) was also significantly different (P = 0.010) with 69.6 % sensitivity and 70.6 % specificity respectively. No significant difference was found among N stages. The two sets of k ( ep )s were highly correlated (r = 0.809, P < 0.001). Forty-three patients had chemoradiation, one palliative chemotherapy and one radiotherapy only. In the four patients with poor outcome, k ( el, ) E ( R, ) MaxEn and iAUC tended to be higher. CONCLUSIONS: Neovasculature in higher T stage NPC exhibits some parameters of increased permeability and perfusion. Thus, DCE-MRI may be helpful as an adjunctive technique in evaluating NPC. KEY POINTS : • The correct assessment of nasopharyngeal carcinoma (NPC) is important for planning treatment. • Neovasculature in higher T stage NPC exhibits increased permeability and perfusion. • Correlation between quantitative and semi-quantitative analysis validates the robustness of DCE-MRI. • DCE-MRI may be helpful as an adjunctive parameter in evaluating NPC.
    European Radiology 02/2013; · 4.34 Impact Factor
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    ABSTRACT: To assess the awareness of radiation dose and associated risks caused by radiological procedures among local patients. All subjects were recruited by randomly sampling the patients receiving radiological examinations. These subjects were stratified on age, sex and education. The questionnaire was in Chinese and consisted of 28 questions mostly in multiple choice/true-or-false format, divided into three sections examining demographic data, radiation knowledge/awareness and expectations. A total of 173 questionnaires were returned (83 females and 84 females; mean age of 53). Of these, 32.6% had attended college, 32.6% had completed matriculation and 24.4% secondary school. Most subjects underwent CT (75), MRI (70) and PET-CT (18). Education significantly affected the radiation knowledge (P = 0.013). 60.7% and 32.7% were not aware of the radiation-free nature of MRI and USG, respectively. Respectively, 45.4% and 43.5% were of the misconception that Barium enema and Barium swallow studies do not involve radiation. Moreover, 77.6% and 87.9% were aware of the radiation-laden nature of CT and plain X-rays, respectively. Furthermore, 34% and 50%, respectively, think that they are not exposed to radiation at home and on a plane. Regarding the fatal cancer risk from CT, 17.8% chose the correct answer and 62% underestimated the risk. 32.2% correctly estimated the equivalent dose of CT in terms of number of conventional X-rays and 43.2% underestimated the dose. Most (98.2%) were told of the indication, and 42.7% were told the associated radiation dose. Patient radiation awareness is unsatisfactory. There is need to increase patient radiation awareness, and to provide them with the necessary information.
    Journal of Medical Imaging and Radiation Oncology 02/2013; 57(1):38-44. · 0.98 Impact Factor
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    ABSTRACT: OBJECT: Diffusional kurtosis imaging (DKI), a natural extension of diffusion tensor imaging (DTI), can characterize non-Gaussian diffusion in the brain. We investigated the capability of DKI parameters for detecting microstructural changes in both gray matter (GM) and white matter (WM) in patients with mild cognitive impairment (MCI) and Alzheimer's disease (AD) and sought to determine whether these DKI parameters could serve as imaging biomarkers to indicate the severity of cognitive deficiency. MATERIALS AND METHODS: DKI was performed on 18AD patients and 12 MCI patients. Fractional anisotropy, kurtosis and diffusivity parameters in the temporal, parietal, frontal and occipital lobes were compared between the two groups using Mann-Whitney U test. The correlations between regional DKI parameters and mini-mental state examination (MMSE) score were tested using Pearson's correlation. RESULTS: In ADs, significantly increased diffusivity and decreased kurtosis parameters were observed in both the GM and WM of the parietal and occipital lobes as compared to MCIs. Significantly decreased fractional anisotropy was also observed in the WM of these lobes in ADs. With the exception of fractional anisotropy and radial kurtosis, all the five other DKI parameters exhibited significant correlations with MMSE score in both GW and WM. CONCLUSION: Bearing additional information, the DKI model can provide sensitive imaging biomarkers for assessing the severity of cognitive deficiency in reference to MMSE score and potentially improve early detection and progression monitoring of AD based on characterizing microstructures in both the WM and especially the GM.
    Magnetic Resonance Imaging 01/2013; · 2.06 Impact Factor
  • Nan-Jie Gong, Chun-Sing Wong, Yiu-Ching Chu, Jing Gu
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    ABSTRACT: We compared the parameters derived from diffusion-weighted imaging (DWI) and positron emission tomography/computed tomography (PET/CT) for treatment response evaluation and response prediction in patients with gastrointestinal stromal tumor (GIST). Seven patients with histologically proven metastatic disease were enrolled. DWI and PET/CT data were collected from all patients at diagnosis and from six at follow-up. All 37 lesions were identifiable in DWI with a sensitivity of 100%. To achieve higher accuracy, we used the apparent diffusion coefficient (ADC) of liver and background noise as thresholds for the measurement of the ADCs of lesions. Significant inverse correlations were found between ADC(mean_thr) (ADC(mean) with thresholds) and SUV(mean) (mean standardized uptake value) (R(2)  = 0.523, p < 0.001 at diagnosis, and R(2)  = 0.916, p < 0.001 at follow-up), between ADC(mean_thr) and SUV(max) (maximum SUV) (R(2)  = 0.529, p < 0.001 at diagnosis, and R(2)  = 0.761, p < 0.001 at follow-up), between ΔADC(mean_thr) (percentage change in ADC(mean_thr) ) and ΔSUV(mean) (percentage change in SUV(mean) ) (R(2)  = 0.384, p < 0.001), and between ΔADC(mean_thr) and ΔSUV(max) (percentage change in SUV(max) ) (R(2)  = 0.500, p < 0.001). In lesion-based analysis, pre-treatment ADC(mean_thr) outperformed SUV(mean) and SUV(max) in treatment response prediction, with an area under the receiver operating characteristic curve of 0.706. These results show that DWI can provide a quantitative assessment comparable with PET/CT in GIST lesion characterization, treatment response evaluation and response prediction. Copyright © 2012 John Wiley & Sons, Ltd.
    NMR in Biomedicine 07/2012; · 3.45 Impact Factor
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    ABSTRACT: In this preliminary study, we aimed to investigate the abnormalities of water diffusion in children with temporal lobe epilepsy (TLE). Eight children with unilateral TLE (according to electroencephalography, EEG) and eight age- and sex-matched controls were recruited. Diffusion tensor imaging (DTI)/diffusional kurtosis imaging (DKI) acquisitions were performed. Radial diffusivity (λ(⊥) ), axial diffusivity (λ(∥) ), mean diffusivity (MD) and fractional anisotropy (FA) maps were calculated for both DTI and DKI, and radial kurtosis (K(⊥) ), axial kurtosis (K(∥) ) and mean kurtosis (MK) maps were calculated for DKI only. Mann-Whitney test showed that, for white matter in the temporal lobe, DKI-derived λ(∥) , MD and K(∥) were significantly different in bilateral temporal lobes and EEG-abnormal and EEG-normal sides of the temporal lobe between patients and controls, whereas DTI showed no abnormalities. For gray matter, DKI detected significantly higher MD and MK in the same three comparisons, whereas DTI detected abnormalities only in the comparison between bilateral temporal lobes and between EEG-normal sides in cases and left-right matched sides in controls. No significant difference was observed between EEG-abnormal and EEG-normal sides in cases. These preliminary results indicate that DKI is more sensitive than DTI for the detection of diffusion abnormalities in the temporal lobes of children with TLE, even when EEG signals are normal. These findings pave the way for the application of DKI for in-depth studies on TLE in children. Copyright © 2012 John Wiley & Sons, Ltd.
    NMR in Biomedicine 06/2012; 25(12):1369-77. · 3.45 Impact Factor
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    ABSTRACT: To investigate the optimal PET protocol and analytical method to characterize the glucose metabolism in nasopharyngeal carcinoma (NPC). Newly diagnosed NPC patients were recruited and a dynamic PET-CT scan was performed. The optimized threshold to derive the arterial input function (AIF) was studied. Two-tissue compartmental kinetic modeling using three, four, and five parameters, Patlak graphical analysis, and time sensitivity (S-factor) analysis were performed. The best compartmental model was determined in terms of goodness of fit, and correlated with Ki from Patlak graphical analysis and the S-factor. The methods with R>0.9 and P<0.05 were considered acceptable. The protocols using two static scans with its retention index (RI=(SUV(2)/SUV(1)-1)×100%, where SUV is the standardized uptake value) were also studied and compared with S-factor analysis. The best threshold of 0.6 was determined and used to derive AIF. The kinetic model with five parameters yields the best statistical results, but the model with k4=0 was used as the gold standard. All Ki values and some S-factors from data between various intervals (10-30, 10-45, 15-30, 15-45, 20-30, and 20-45 min) fulfilled the criteria. The RIs calculated from the S-factor were highly correlated to RI derived from simple two-point static scans at 10 and 30 min (R=0.9, P<0.0001). The Patlak graphical analyses and even a 20-min-interval S-factor analysis or simple two-point static scans were shown to be sufficient to characterize NPC metabolism, confirming the clinical feasibility of applying a short dynamic with image-derived AIF or simple two-point static PET scans for studying NPC.
    Nuclear Medicine Communications 11/2011; 33(2):191-7. · 1.38 Impact Factor
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    Chun-Sing Wong, Yiu-Ching Chu
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    ABSTRACT: With the evolution of immunochemical staining techniques and better imaging modalities with better image resolution and whole body coverage, gastrointestinal stromal tumor (GIST), the most common mesenchymal tumor of the gastrointestinal tract, is often encountered in clinical practice. Metastasis is common with malignant GIST and can be found in up to 50% of patients at presentation. Liver and peritoneum are the two most common sites of metastasis and accounted for 95% of cases. Lymphatics, bone and lung metastasis are rare. Malignant GIST with intracranial metastasis is even rarer, with only a few cases reported in the literature, and most of these had earlier metastasis elsewhere. Radiological features for GISTs are not specific but it does contribute to confirming early and accurate diagnosis of malignant GISTs by judging the tumor size, enhancement pattern and the invasion of adjacent structures. We report a case of a 26-year-old male with metastatic GIST to the liver and subsequently to the brain and skull vault. This is the first case reported in our locality and he is the youngest patient reported with this disease entity. The clinical progress, radiological features and the role of imaging will be discussed further in this paper. The radiological and clinical features of the primary tumor will specifically be addressed. The purpose of this paper is to enrich the current database of this rare disease entity and to alert both radiologists and clinicians about the imaging features of GIST with intracranial metastasis.
    Chinese medical journal 11/2011; 124(21):3595-7. · 0.90 Impact Factor
  • European Journal Of Haematology 08/2011; 88(3):275-6. · 2.55 Impact Factor
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    Journal of Clinical Oncology 05/2011; 29(20):e610-2. · 18.04 Impact Factor
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    ABSTRACT: Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the gastrointestinal tract. It can be benign or malignant in behavior. Stomach, being the most common site (70%) for GISTs, is followed by the small intestine (20%). Anorectal, colonic, and esophageal GISTs are uncommon, whereas extraintestinal GISTs are extremely rare. The presenting symptoms are highly dependent on tumor size and location, although a large number of GISTs are asymptomatic. The purpose of this article is to highlight the unusual characteristics of GISTs illustrated by PET/CT and CT imaging. These characteristics are organized into (1) unusual tumor location, (2) unusual clinical presentation, and (3) unusual sites of metastasis. Knowing the uncommon features of GISTs is important, as they are more often seen nowadays with the increasingly important role of PET/CT and CT in GIST management; and these tumors are associated with a poorer prognosis and unwanted delay in diagnosis is avoidable. With the availability of effective treatment by imatinib mesylate, a prompt and early diagnosis is essential for disease control. All GISTs illustrated in this article are pathologically proven.
    Clinical nuclear medicine 03/2011; 36(3):e1-7. · 3.92 Impact Factor
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    ABSTRACT: To assess the knowledge and practice pertaining to radiation exposure related to radiological imaging among medical doctors, in relation to specialty and year of experience. Questionnaires as recommended by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) were distributed to doctors in tertiary hospitals by convenience sampling. Their knowledge of radiation doses of common radiological investigations was assessed by any significant difference from correct answers by sampled t-test. Comparison between specialties and between the more (>6 years experience) and less experienced doctors was made by pairwise comparisons of 'right answer minus mean difference (RMD)' using Wilcoxon Signed Ranks Test. Descriptive analysis of their knowledge of harmful effects of radiation and the practices pertaining were also performed. Total 93 questionnaires were sent out and 82 (88.2%, 40 interns, 24 clinicians, 18 radiologists) were returned. Radiologists had the least deviation from correct answers compared to interns (1.29 vs. 2.40, p=0.018) and physicians (1.29 vs. 2.57, p=0.046). More-experienced doctors also performed better than the less-experienced (1.69 vs. 2.57, p=0.027). 12/80 (15%) and 4/80 (5%) failed to recognize MR and US as radiation-free modalities. Only 10/80 (12.5%) knew the risk of carcinogenesis from abdominal CT and only 4/81 (5%) will discuss radiation-related hazard with patients routinely. Knowledge of medical doctors, including radiologists, towards radiation exposure of imaging is unsatisfactory and could imply a tendency of radiation misuse and under-utilization of alternative radiation-free methods. On-job training and discussion of the radiation risk with patients are advised.
    European journal of radiology 03/2011; 81(3):e264-8. · 2.65 Impact Factor