Displaying publications 181 - 200 of 288 in total

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  1. Trend and impact of international collaboration in clinical medicine papers published in Malaysia
    Low WY, Ng KH, Kabir MA, Koh AP, Sinnasamy J
    Scientometrics, 2014;98:1521-1533.
    PMID: 24465065
    Research collaboration is the way forward in order to improve quality and impact of its research findings. International research collaboration has resulted in international co-authorship in scientific communications and publications. This study highlights the collaborating research and authorship trend in clinical medicine in Malaysia from 2001 to 2010. Malaysian-based author affiliation in the Web of Science (Science Citation Index Expanded) and clinical medicine journals (n = 999) and articles (n = 3951) as of 30th Oct 2011 were downloaded. Types of document analyzed were articles and reviews, and impact factors (IF) in the 2010 Journal Citation Report Science Edition were taken to access the quality of the articles. The number of publications in clinical medicine increased from 4.5 % (n = 178) in 2001 to 23.9 % (n = 944) in 2010. The top three contributors in the subject categories are Pharmacology and Pharmacy (13.9 %), General and Internal Medicine (13.6 %) and Tropical Medicine (7.3 %). By journal tier system: Tier 1 (18.7 %, n = 738), Tier 2 (22.5 %, n = 888), Tier 3 (29.6 %, n = 1170), Tier 4 (27.2 %, n = 1074), and journals without IF (2.1 %, n = 81). University of Malaya was the most productive. Local collaborators accounted for 60.3 % and international collaborations 39.7 %. Articles with international collaborations appeared in journals with higher journal IFs than those without international collaboration. They were also cited more significantly than articles without international collaborations. Citations, impact factor and journal tiers were significantly associated with international collaboration in Malaysia's clinical medicine publications. Malaysia has achieved a significant number of ISI publications in clinical medicine participation in international collaboration.
  2. Identifying factors associated with diagnostic concordance/discordance in oral lichen planus
    Siar CH, Lim JS, Tang SP, Chia HS, Loh YM, Ng KH
    J Oral Maxillofac Surg, 2013 Oct;71(10):1688-93.
    PMID: 23773425 DOI: 10.1016/j.joms.2013.04.026
    To identify factors associated with concordance and discordance between clinical and histopathologic diagnoses of oral lichen planus lesions.
  3. Fusion of gamma scintigraphic and magnetic resonance images improves the anatomical delineation of radiotracer for the assessment of gastrointestinal transit
    Yeong CH, Abdullah BJ, Ng KH, Chung LY, Goh KL, Perkins AC
    Nucl Med Commun, 2013 Jul;34(7):645-51.
    PMID: 23612704 DOI: 10.1097/MNM.0b013e32836141e4
    This paper describes the use of gamma scintigraphic and magnetic resonance (MR) fusion images for improving the anatomical delineation of orally administered radiotracers used in gastrointestinal (GI) transit investigations.
  4. Cementum status in natural teeth opposing implant-borne bridgework in Macaca fascicularis
    Siar CH, Pua CK, Toh CG, Romanos G, Ng KH
    Oral Surg Oral Med Oral Pathol Oral Radiol, 2012 Nov;114(5 Suppl):S46-53.
    PMID: 23083955 DOI: 10.1016/j.tripleo.2011.07.049
    The objective of this study was to investigate the cementum status in natural teeth opposing implant-supported bridgework.
  5. Dual-source CT coronary angiography: effectiveness of radiation dose reduction with lower tube voltage
    Sabarudin A, Md Yusof AK, Tay MF, Ng KH, Sun Z
    Radiat Prot Dosimetry, 2013;153(4):441-7.
    PMID: 22807493 DOI: 10.1093/rpd/ncs127
    This study was conducted to investigate the effectiveness of dose-saving protocols in dual-source computed tomography (CT) coronary angiography compared with invasive coronary angiography (ICA). On 50 patients who underwent coronary CT angiography was performed dual-source CT (DSCT) and compared with ICA procedures. Entrance skin dose (ESD), which was measured at the thyroid gland, and effective dose (E) were assessed for both imaging modalities. The mean ESD measured at the thyroid gland was the highest at 120 kVp, followed by the 100 kVp DSCT and the ICA protocols with 4.0±1.8, 2.7±1.0 and 1.1±1.2 mGy, respectively. The mean E was estimated to be 10.3±2.1, 6.2±2.3 and 5.3±3.4 mSv corresponding to the 120-kVp, 100-kVp DSCT and ICA protocols, respectively. The application of 100 kVp in DSCT coronary angiography is feasible only in patients with a low body mass index of <25 kg m(-2), which leads to a significant dose reduction with the radiation dose being equivalent to that of ICA.
  6. Differential expression of canonical and non-canonical Wnt ligands in ameloblastoma
    Siar CH, Nagatsuka H, Han PP, Buery RR, Tsujigiwa H, Nakano K, et al.
    J Oral Pathol Med, 2012 Apr;41(4):332-9.
    PMID: 22077561 DOI: 10.1111/j.1600-0714.2011.01104.x
    Canonical and non-canonical Wnt signaling pathways modulate diverse cellular processes during embryogenesis and post-natally. Their deregulations have been implicated in cancer development and progression. Wnt signaling is essential for odontogenesis. The ameloblastoma is an odontogenic epithelial neoplasm of enamel organ origin. Altered expressions of Wnts-1, -2, -5a, and -10a are detected in this tumor. The activity of other Wnt members remains unclarified.
  7. Reproducibility of neutron activated Sm-153 oral dose formulations intended for human administration
    Yeong CH, Blackshaw PE, Ng KH, Abdullah BJ, Blaauw M, Dansereau RJ, et al.
    Appl Radiat Isot, 2011 Sep;69(9):1181-4.
    PMID: 21550260 DOI: 10.1016/j.apradiso.2011.04.017
    Neutron activation of Sm-152 offers a method of radiolabeling for the in vivo study of oral dose formulations by gamma scintigraphy. Reproducibility measurements are needed to ensure the robustness of clinical studies. 204 enteric-coated guaifenesin core tablets (10mg of Sm(2)O(3)) were irradiated by thermal neutrons to achieve 1 MBq at 48 h. Administered activities were 0.86±0.03 MBq. Good reproducibility (CV=3.5%) was observed over 24 weeks ensuring that volunteer doses were within the dose reference level of 0.8 mSv.
  8. Notch4 overexpression in ameloblastoma correlates with the solid/multicystic phenotype
    Siar CH, Nagatsuka H, Chuah KS, Rivera RS, Nakano K, Ng KH, et al.
    Oral Surg Oral Med Oral Pathol Oral Radiol Endod, 2010 Aug;110(2):224-33.
    PMID: 20659700 DOI: 10.1016/j.tripleo.2010.03.009
    Notch signaling has been implicated in cell fate decisions during odontogenesis and tumorigenesis of some odontogenic neoplasms; however, its role in solid/multicystic (SA), unicystic (UA), and recurrent (RA) ameloblastoma remains unclear. The aim of this study was to determine Notch receptor and ligand expressions in these subtypes and to speculate on their significance.
  9. Differential expression of Notch receptors and their ligands in desmoplastic ameloblastoma
    Siar CH, Nakano K, Han PP, Nagatsuka H, Ng KH, Kawakami T
    J Oral Pathol Med, 2010 Aug 1;39(7):552-8.
    PMID: 20337864 DOI: 10.1111/j.1600-0714.2009.00871.x
    In mammals, the Notch gene family encodes four receptors (Notch1-4), and all of them are important for cell fate decisions. Notch signaling pathway plays an essential role in tooth development. The ameloblastoma, a benign odontogenic epithelial neoplasm, histologically recapitulates the enamel organ at bell stage. Notch has been detected in the plexiform and follicular ameloblastoma. Its activity in the desmoplastic ameloblastoma is unknown.
  10. A low cost solution for post-biopsy complications using available RFA generator and coaxial core biopsy needle
    Azlan CA, Mohd Nasir NF, Saifizul AA, Faizul MS, Ng KH, Abdullah BJ
    Australas Phys Eng Sci Med, 2007 Dec;30(4):288-91.
    PMID: 18274069
    Percutaneous image-guided needle biopsy is typically performed in highly vascular organs or in tumours with rich macroscopic and microscopic blood supply. The main risks related to this procedure are haemorrhage and implantation of tumour cells in the needle tract after the biopsy needle is withdrawn. From numerous conducted studies, it was found that heating the needle tract using alternating current in radiofrequency (RF) range has a potential to minimize these effects. However, this solution requires the use of specially designed needles, which would make the procedure relatively expensive and complicated. Thus, we propose a simple solution by using readily available coaxial core biopsy needles connected to a radiofrequency ablation (RFA) generator. In order to do so, we have designed and developed an adapter to interface between these two devices. For evaluation purpose, we used a bovine liver as a sample tissue. The experimental procedure was done to study the effect of different parameter settings on the size of coagulation necrosis caused by the RF current heating on the subject. The delivery of the RF energy was varied by changing the values for delivered power, power delivery duration, and insertion depth. The results showed that the size of the coagulation necrosis is affected by all of the parameters tested. In general, the size of the region is enlarged with higher delivery of RF power, longer duration of power delivery, and shallower needle insertion and become relatively constant after a certain value. We also found that the solution proposed provides a low cost and practical way to minimizes unwanted post-biopsy effects.
  11. Entrance surface dose and image quality: comparison of adult chest and abdominal X-ray examinations in general practitioner clinics, public and private hospitals in Malaysia
    Hambali AS, Ng KH, Abdullah BJ, Wang HB, Jamal N, Spelic DC, et al.
    Radiat Prot Dosimetry, 2009 Jan;133(1):25-34.
    PMID: 19223292 DOI: 10.1093/rpd/ncp007
    This study was undertaken to compare the entrance surface dose (ESD) and image quality of adult chest and abdominal X-ray examinations conducted at general practitioner (GP) clinics, and public and private hospitals in Malaysia. The surveyed facilities were randomly selected within a given category (28 GP clinics, 20 public hospitals and 15 private hospitals). Only departmental X-ray units were involved in the survey. Chest examinations were done at all facilities, while only hospitals performed abdominal examinations. This study used the x-ray attenuation phantoms and protocols developed for the Nationwide Evaluation of X-ray Trends (NEXT) survey program in the United States. The ESD was calculated from measurements of exposure and clinical geometry. An image quality test tool was used to evaluate the low-contrast detectability and high-contrast detail performance under typical clinical conditions. The median ESD value for the adult chest X-ray examination was the highest (0.25 mGy) at GP clinics, followed by private hospitals (0.22 mGy) and public hospitals (0.17 mGy). The median ESD for the adult abdominal X-ray examination at public hospitals (3.35 mGy) was higher than that for private hospitals (2.81 mGy). Results of image quality assessment for the chest X-ray examination show that all facility types have a similar median spatial resolution and low-contrast detectability. For the abdominal X-ray examination, public hospitals have a similar median spatial resolution but larger low-contrast detectability compared with private hospitals. The results of this survey clearly show that there is room for further improvement in performing chest and abdominal X-ray examinations in Malaysia.
  12. Quantitative assessment of breast density from digitized mammograms into Tabar's patterns
    Jamal N, Ng KH, Looi LM, McLean D, Zulfiqar A, Tan SP, et al.
    Phys Med Biol, 2006 Nov 21;51(22):5843-57.
    PMID: 17068368
    We describe a semi-automated technique for the quantitative assessment of breast density from digitized mammograms in comparison with patterns suggested by Tabar. It was developed using the MATLAB-based graphical user interface applications. It is based on an interactive thresholding method, after a short automated method that shows the fibroglandular tissue area, breast area and breast density each time new thresholds are placed on the image. The breast density is taken as a percentage of the fibroglandular tissue to the breast tissue areas. It was tested in four different ways, namely by examining: (i) correlation of the quantitative assessment results with subjective classification, (ii) classification performance using the quantitative assessment technique, (iii) interobserver agreement and (iv) intraobserver agreement. The results of the quantitative assessment correlated well (r2 = 0.92) with the subjective Tabar patterns classified by the radiologist (correctly classified 83% of digitized mammograms). The average kappa coefficient for the agreement between the readers was 0.63. This indicated moderate agreement between the three observers in classifying breast density using the quantitative assessment technique. The kappa coefficient of 0.75 for intraobserver agreement reflected good agreement between two sets of readings. The technique may be useful as a supplement to the radiologist's assessment in classifying mammograms into Tabar's pattern associated with breast cancer risk.
  13. Pediatric melioidosis in Pahang, Malaysia
    How HS, Ng KH, Yeo HB, Tee HP, Shah A
    J Microbiol Immunol Infect, 2005 Oct;38(5):314-9.
    PMID: 16211138
    Melioidosis is much less common in children than in adults. This study investigated the incidence, demographic characteristics, presenting symptoms and outcome of pediatric melioidosis in Pahang, Malaysia. This retrospective study included patients < or =18 years old with positive body fluid cultures for Burkholderia pseudomallei from January 2000 to June 2003. Data on culture results were obtained from 2 referral hospitals. The incidence of pediatric melioidosis was 0.68/100,000 population per year. Of the 13 patients identified during the study period, 10 were male; 9 were Malays, 2 were Indians and 2 were aborigines. The mean age of these patients was 9.5 +/- 5.4 years. None of the patients had a previous history of confirmed melioidosis or predisposing factors for infection. Localized melioidosis was the most common presentation (46.2%) followed by melioidosis with septic shock (38.4%). Among patients with localized melioidosis, head and neck involvement (83.3%) was the most common presentation (2 patients with cervical abscesses, 1 with submandibular abscesses and 2 with acute suppurative parotitis) and another patient had right axillary abscess. All of the patients with septic shock had pneumonia and 2 of them had multi-organ involvement. The mortality among patients with septic shock was 80% and death occurred within 24 h of admission in all cases. In contrast, no complications or death occurred among patients with localized melioidosis. Melioidosis with septic shock is less common than localized melioidosis in pediatric patients, but is associated with very high mortality.
  14. Invadopodia proteins, cortactin, N-WASP and WIP differentially promote local invasiveness in ameloblastoma
    Siar CH, Rahman ZA, Tsujigiwa H, Mohamed Om Alblazi K, Nagatsuka H, Ng KH
    J Oral Pathol Med, 2016 Sep;45(8):591-8.
    PMID: 26752341 DOI: 10.1111/jop.12417
    BACKGROUND: Cell migration and invasion through interstitial tissues are dependent upon several specialized characteristics of the migratory cell notably generation of proteolytic membranous protrusions or invadopodia. Ameloblastoma is a benign odontogenic epithelial neoplasm with a locally infiltrative behaviour. Cortactin and MMT1-MMP are two invadopodia proteins implicated in its local invasiveness. Other invadopodia regulators, namely N-WASP, WIP and Src kinase remain unclarified. This study addresses their roles in ameloblastoma.

    MATERIALS AND METHOD: Eighty-seven paraffin-embedded ameloblastoma cases (20 unicystic, 47 solid/multicystic, 3 desmoplastic and 17 recurrent) were subjected to immunohistochemistry for expression of cortactin, N-WASP, WIP, Src kinase and F-actin, and findings correlated with clinicopathological parameters.

    RESULTS: Invadopodia proteins (except Src kinase) and F-actin were widely detected in ameloblastoma (cortactin: n = 73/87, 83.9%; N-WASP: n = 59/87; 67.8%; WIP: n = 77/87; 88.5%; and F-actin: n = 87/87, 100%). Protein localization was mainly cytoplasmic and/or membranous, and occasionally nuclear for F-actin. Cortactin, which functions as an actin-scaffolding protein, demonstrated significantly higher expression levels within ameloblastoma tumoral epithelium than in stroma (P < 0.05). N-WASP, which coordinates actin polymerization and invadopodia-mediated extracellular matrix degradation, was overexpressed in the solid/multicystic subtype (P < 0.05). WIP, an upstream regulator of N-WASP, and F-actin were significantly upregulated along the tumour invasive front compared to tumour centres (P < 0.05). Except for males with cortactin overexpression, other clinical parameters (age, ethnicity and anatomical site) showed no significant correlations.

    CONCLUSIONS: Present results suggest that local invasiveness of ameloblastoma is dependent upon the migratory potential of its tumour cells as defined by their distribution of cortactin, N-WASP and WIP in correlation with F-actin cytoskeletal dynamics.

  15. Application of wavelet techniques for cancer diagnosis using ultrasound images: A Review
    Sudarshan VK, Mookiah MR, Acharya UR, Chandran V, Molinari F, Fujita H, et al.
    Comput Biol Med, 2016 Feb 1;69:97-111.
    PMID: 26761591 DOI: 10.1016/j.compbiomed.2015.12.006
    Ultrasound is an important and low cost imaging modality used to study the internal organs of human body and blood flow through blood vessels. It uses high frequency sound waves to acquire images of internal organs. It is used to screen normal, benign and malignant tissues of various organs. Healthy and malignant tissues generate different echoes for ultrasound. Hence, it provides useful information about the potential tumor tissues that can be analyzed for diagnostic purposes before therapeutic procedures. Ultrasound images are affected with speckle noise due to an air gap between the transducer probe and the body. The challenge is to design and develop robust image preprocessing, segmentation and feature extraction algorithms to locate the tumor region and to extract subtle information from isolated tumor region for diagnosis. This information can be revealed using a scale space technique such as the Discrete Wavelet Transform (DWT). It decomposes an image into images at different scales using low pass and high pass filters. These filters help to identify the detail or sudden changes in intensity in the image. These changes are reflected in the wavelet coefficients. Various texture, statistical and image based features can be extracted from these coefficients. The extracted features are subjected to statistical analysis to identify the significant features to discriminate normal and malignant ultrasound images using supervised classifiers. This paper presents a review of wavelet techniques used for preprocessing, segmentation and feature extraction of breast, thyroid, ovarian and prostate cancer using ultrasound images.
  16. Optimization of dose and image quality of paediatric cardiac catheterization procedure
    Lubis LE, Bayuadi I, Pawiro SA, Ng KH, Bosmans H, Soejoko DS
    Phys Med, 2015 Nov;31(7):659-68.
    PMID: 26050060 DOI: 10.1016/j.ejmp.2015.05.011
    The purpose of this study is to quantify the quality of the available imaging modes for various iodine-based contrast agent concentration in paediatric cardiology. The figure of merit (FOM) was defined as the squared signal to noise ratio divided by a patient dose related parameter. An in house constructed phantom simulated a series of vessel segments with iodine concentrations from 10% or 30 mg/cc to 16% or 48 mg/cc of iodine in a blood plasma solution, all within the dimensional constraints of a paediatric patient. The phantom also used test inserts of tin (Sn). Measurements of Entrance Surface Air Kerma (ESAK) and exit dose rate were performed along with calculations of the signal-to-noise ratio (SNR) of all the objects. A first result showed that it was favourable to employ low dose fluoroscopy mode and lower frame rate modes in cine acquisition if dynamic information is not critical. Normal fluoroscopy dose mode provided a considerably higher dose level (in comparison to low dose mode) with only a slight improvement in SNR. Higher frame rate cine modes should be used however when the clinical situation dictates so. This work also found that tin should not be intended as iodine replacement material for research purposes due to the mismatching SNR, particularly on small vessel sizes.
  17. Characterization of a MOSkin detector for in vivo skin dose measurements during interventional radiology procedures
    Safari MJ, Wong JH, Ng KH, Jong WL, Cutajar DL, Rosenfeld AB
    Med Phys, 2015 May;42(5):2550-8.
    PMID: 25979047 DOI: 10.1118/1.4918576
    The MOSkin is a MOSFET detector designed especially for skin dose measurements. This detector has been characterized for various factors affecting its response for megavoltage photon beams and has been used for patient dose measurements during radiotherapy procedures. However, the characteristics of this detector in kilovoltage photon beams and low dose ranges have not been studied. The purpose of this study was to characterize the MOSkin detector to determine its suitability for in vivo entrance skin dose measurements during interventional radiology procedures.
  18. Fulltext A Study of Dielectric Properties of Proteinuria between 0.2 GHz and 50 GHz
    Mun PS, Ting HN, Ong TA, Wong CM, Ng KH, Chong YB
    PLoS One, 2015;10(6):e0130011.
    PMID: 26066351 DOI: 10.1371/journal.pone.0130011
    This paper investigates the dielectric properties of urine in normal subjects and subjects with chronic kidney disease (CKD) at microwave frequency of between 0.2 GHz and 50 GHz. The measurements were conducted using an open-ended coaxial probe at room temperature (25°C), at 30°C and at human body temperature (37°C). There were statistically significant differences in the dielectric properties of the CKD subjects compared to those of the normal subjects. Statistically significant differences in dielectric properties were observed across the temperatures for normal subjects and CKD subjects. Pearson correlation test showed the significant correlation between proteinuria and dielectric properties. The experimental data closely matched the single-pole Debye model. The relaxation dispersion and relaxation time increased with the proteinuria level, while decreasing with the temperature. As for static conductivity, it increased with proteinuria level and temperature.
  19. Doses to patients in routine X-ray examinations in Malaysia
    Ng KH, Rassiah P, Wang HB, Hambali AS, Muthuvellu P, Lee HP
    Br J Radiol, 1998 Jun;71(846):654-60.
    PMID: 9849390
    A collaborative national survey initiated by the University of Malaya and the Ministry of Health was conducted from 1993 to 1995 to establish baseline patient dose data for seven common types (12 projections) of X-ray examinations in Malaysia. A total of 12 randomly selected public hospitals and 867 patients were included in this survey. The entrance surface doses (ESD) received by the patients were measured using thermoluminescent dosemeters (TLDs) attached to the patient's skin. Histograms are presented showing wide, positively skewed distributions of measured entrance surface doses for each examination. Mean, median, first and third quartile values of ESD and median effective dose are reported. Survey results are generally comparable with those reported in the UK, USA and by the International Atomic Energy Agency (IAEA). The results also provide information on dose level for a lower weight population (mean weight 60 kg) compared with the international reference dose values based on a 70 kg standard. The findings support the importance of the on-going national quality assurance programme to ensure doses are kept to a level consistent with optimum image quality. The data will also be useful for the formulation of national guidance levels as recommended by the IAEA. Furthermore, this study provides patient dosimetry information on healthcare level II countries.
  20. Differentiation of elemental composition of normal and malignant breast tissue by instrumental neutron activation analysis
    Ng KH, Bradley DA, Looi LM, Mahmood CS, Wood AK
    Appl Radiat Isot, 1993 Mar;44(3):511-6.
    PMID: 8472024
    Multi-elemental quantitative analyses of 15 paired samples of normal and malignant human breast tissue by instrumental neutron activation analysis are reported. The elements, Al, Br, Ca, Cl, Co, Cs, Fe, K, Na, Rb, Zn were detected. Significantly elevated concentration levels were found for Al, Br, Ca, Cl, Cs, K, Na, Zn in malignant compared to normal tissue. Although the role of elemental composition in breast cancer is unclear, this finding may be of importance as another parameter for differentiating normal from malignant tissue.
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