Douglas K.S. Ng

The University of Hong Kong, Hong Kong, Hong Kong

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Publications (2)5.73 Total impact

  • Fuk-Hay Tang · Douglas K.S. Ng · Daniel H.K. Chow ·
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    ABSTRACT: We present a computer-aided detection (CAD) scheme for early detection of ischemic stroke with small lesions using image feature characteristics. A novel Circular Adaptive Region of Interest (CAROI) method is proposed to analyze the Computed Tomography (CT) images of the brain. Our result indicates that for the emergency physicians and radiology residents, there is a significant improvement in sensitivity and specificity when using CAD (P < 0.005). A mathematical model is established incorporating the weighting of the feature changes. Our CAD scheme is promising for early detection of ischemic stroke and helps improve the efficiency and accuracy of clinical practice.
    Computers in Biology and Medicine 07/2011; 41(7):529-36. DOI:10.1016/j.compbiomed.2011.05.001 · 1.24 Impact Factor
  • Michael Ying · Douglas K S Ng · Dennis M C Yung · Esther S T Lee ·
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    ABSTRACT: Ultrasound is a useful imaging tool in the assessment of thyroid glands, and Doppler ultrasound helps in the evaluation of thyroid vascularity. This study was undertaken to evaluate the difference in the thyroid vascularity demonstrated on the state-of-the-art high-sensitivity power Doppler sonography (HSPDS) and the conventional power Doppler sonography (PDS), and to investigate the feasibility of using a customized algorithm with image-processing software for semi-quantitative assessment of thyroid vascularity. A total of 25 healthy volunteers were included in the study, and each subject had two thyroid ultrasound examinations with HSPDS and PDS, respectively. High sensitivity and conventional power Doppler sonograms of the thyroid glands were taken and recorded. To evaluate the vascularity of thyroid lobes quantitatively, a customized algorithm using the software Matlab was developed and used to analyze the ultrasound images. The vascularity of thyroid lobe (i.e., region of interest, ROI) was expressed as the vascular index (VI), which is the ratio of the number of color pixels to the total number of pixels within the ROI. Results showed that thyroid vascularity was detected in all thyroid lobes on both HSPDS and PDS. The mean VI of the thyroid lobes on HSPDS (right lobe, 0.31 +/- 0.08; left lobe, 0.32 +/- 0.07) was significantly higher than on PDS (right lobe, 0.18 +/- 0.09; left lobe, 0.16 +/- 0.08) (p < 0.05). There was no significant difference in the VI between the right and left thyroid lobes (p >0.05). On HSPDS, 96% of the thyroid lobes showed a VI <0.5, while 96% of thyroid lobes had a VI <0.3 on PDS. HSPDS is more sensitive than PDS in the detection of thyroid vascularity. The developed algorithm can quantify the color pixels on power Doppler sonograms, which is useful for objective assessment of thyroid vascularity.
    Thyroid: official journal of the American Thyroid Association 09/2009; 19(11):1265-9. DOI:10.1089/thy.2009.0221 · 4.49 Impact Factor