Ng Siew Cheok

Dr. Ng Siew Cheok

Department of Biomedical Engineering, Faculty of Engineering, Universiti Malaya, 50603 Kuala Lumpur, Malaysia
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Research Focus & Metrics

Academic Career Length

35Years (1992-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 January 2014 in The Scientific World Journal
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YJYessi Jusman
Yessi Jusman
NCNg Siew Cheok
Ng Siew Cheok
NONoor Azuan Abu Osman
Noor Azuan Abu Osman
Advent of medical image digitalization leads to image processing and computer-aided diagnosis systems in numerous clinical applications. These technologies could be used to automatically diagnose patient or serve as second opinion to pathologists. This paper briefly reviews cervical screening techniques, advantages, and disadvantages. The digital data of the screening techniques are used as data for the computer screening system as replaced in the expert analysis. Four stages of the computer system are enhancement, features extraction, feature selection, and classification reviewed in detail. The computer system based on cytology data and electromagnetic spectra data achieved better accuracy than other data.

29 August 2017 in Medical & Biological Engineering & Computing
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Amir FaisalAmir Faisal
Amir Faisal
NCNg Siew Cheok
Ng Siew Cheok
SGSiew Li Goh
Siew Li Goh
KLKhin wee Lai
Khin wee Lai

19 May 2009 in IEEE Transactions on Biomedical Engineering
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Journal Article
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NCNg Siew Cheok
Ng Siew Cheok
RPRaveendran Paramesran
Raveendran Paramesran
The mu rhythm is an electroencephalogram (EEG) signal located at the central region of the brain that is frequently used for studies concerning motor activity. Quite often, the EEG data are contaminated with artifacts and the application of blind source separation (BSS) alone is insufficient to extract the mu rhythm component. We present a new two-stage approach to extract the mu rhythm component. The first stage uses second-order blind identification (SOBI) with stationary wavelet transform (SWT) to automatically remove the artifacts. In the second stage, SOBI is applied again to find the mu rhythm component. Our method is first compared with independent component analysis with discrete wavelet transform (ICA-DWT) as well as SOBI-DWT, ICA-SWT, and regression method for artifact removal using simulated EEG data. The results showed that the regression method is more effective in removing electrooculogram (EOG) artifacts, while SOBI-SWT is more effective in removing electromyogram (EMG) artifacts as compared to the other artifact removal methods. Then, all the methods are compared with the direct application of SOBI in extracting mu rhythm components on simulated and actual EEG data from ten subjects. The results showed that the proposed method of SOBI-SWT artifact removal enhances the extraction of the mu rhythm component.

SZShanguang Zhao
Shanguang Zhao
NCNg Siew Cheok
Ng Siew Cheok
SKSelina Khoo
Selina Khoo
ACAiping Chi
Aiping Chi
Synchronization of the dynamic processes in structural networks connect the brain across a wide range of temporal and spatial scales, creating a dynamic and complex functional network. Microstate and omega complexity are two reference-free electroencephalography (EEG) measures that can represent the temporal and spatial complexities of EEG data. Few studies have focused on potential brain spatiotemporal dynamics in the early stages of depression to use as an early screening feature for depression. Thus, this study aimed to explore large-scale brain network dynamics of individuals both with and without subclinical depression, from the perspective of temporal and spatial dimensions and to input them as features into a machine learning framework for the automatic diagnosis of early-stage depression. To achieve this, spatio–temporal dynamics of rest-state EEG signals in female college students (n = 40) with and without (n = 38) subclinical depression were analyzed using EEG microstate and omega complexity analysis. Then, based on differential features of EEGs between the two groups, a support vector machine was utilized to compare performances of spatio–temporal features and single features in the classification of early depression. Microstate results showed that the occurrence rate of microstate class B was significantly higher in the group with subclinical depression when compared with the group without. Moreover, the duration and contribution of microstate class C in the subclinical group were both significantly lower than in the group without subclinical depression. Omega complexity results showed that the global omega complexity of β-2 and γ band was significantly lower for the subclinical depression group compared with the other group (p < 0.05). In addition, the anterior and posterior regional omega complexities were lower for the subclinical depression group compared to the comparison group in α-1, β-2 and γ bands. It was found that AUC of 81% for the differential indicators of EEG microstates and omega complexity was deemed better than a single index for predicting subclinical depression. Thus, since temporal and spatial complexity of EEG signals were manifestly altered in female college students with subclinical depression, it is possible that this characteristic could be adopted as an early auxiliary diagnostic indicator of depression.

8 June 2016 in IEEE/ASME Transactions on Mechatronics
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FJFarahiyah Jasni
Farahiyah Jasni
NHNur Azah Hamzaid
Nur Azah Hamzaid
AMAsan Muthalif
Asan Muthalif
ZZZafirah Zakaria
Zafirah Zakaria
HMHanie Nadia Malaya
Hanie Nadia Malaya
NCNg Siew Cheok
Ng Siew Cheok
This paper presents the design and evaluation of an in-socket sensory system for a transfemoral prosthetic leg using a set of piezoelectric sensors. The design process includes identifying the optimal mounting configuration of the sensors and determining their best placement. Two experiments were performed separately to address each objective. Results of the experiment suggested that cushionall with fit size cantilever with elastic foundation should be adopted to mount the sensors on the socket's wall. As for the placement of the sensors, the result suggested that the sensors should be positioned in zig-zag orientation from top to bottom, which can cover all of the most active area on the quadriceps and hamstring muscle groups. With the identified design, the socket was fabricated and instrumented for a transfemoral amputee and the performance of the in-socket sensory system was evaluated. The amputee performed level walking at normal speed on a 5-m straight pathway multiple times while the output voltage signal from each sensor was recorded. The output signals consistency was assessed by calculating the cross correlation, r, within five trials. In order to measure the strength of the correlation matrix of each sensor, the Frobenius norm, ||A|| F was calculated. The high norm value for all sensors pattern (||A|| F >4.5) for quadriceps implies that the mounting and placement of the sensors is most suitable for a consistent and reliable signal. For Hamstring, results inferred that except for the two sensors located on the top most position and the most bottom sensor, the other sensors showed good performance (||A|| F >4.4). Thus, the proposed design of the in-socket sensory system using piezo sensors was proven to be effective for a transfemoral prosthetic leg.

16 June 2015 in Sensors
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PLPooi Khoon Lim
Pooi Khoon Lim
NCNg Siew Cheok
Ng Siew Cheok
WJWissam Jassim
Wissam Jassim
SRStephen Redmond
Stephen Redmond
MZMuhammad Zilany
Muhammad Zilany
NLNigel Lovell
Nigel Lovell
We present a novel approach to improve the estimation of systolic (SBP) and diastolic blood pressure (DBP) from oscillometric waveform data using variable characteristic ratios between SBP and DBP with mean arterial pressure (MAP). This was verified in 25 healthy subjects, aged 28 ± 5 years. The multiple linear regression (MLR) and support vector regression (SVR) models were used to examine the relationship between the SBP and the DBP ratio with ten features extracted from the oscillometric waveform envelope (OWE). An automatic algorithm based on relative changes in the cuff pressure and neighbouring oscillometric pulses was proposed to remove outlier points caused by movement artifacts. Substantial reduction in the mean and standard deviation of the blood pressure estimation errors were obtained upon artifact removal. Using the sequential forward floating selection (SFFS) approach, we were able to achieve a significant reduction in the mean and standard deviation of differences between the estimated SBP values and the reference scoring (MLR: mean ± SD = −0.3 ± 5.8 mmHg; SVR and −0.6 ± 5.4 mmHg) with only two features, i.e., Ratio2 and Area3, as compared to the conventional maximum amplitude algorithm (MAA) method (mean ± SD = −1.6 ± 8.6 mmHg). Comparing the performance of both MLR and SVR models, our results showed that the MLR model was able to achieve comparable performance to that of the SVR model despite its simplicity.