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Writing a systematic review

Ng KH, Peh WC

Singapore Med J, 2010 May;51(5):362-6.
PMID: 20593139

Evidence-based medicine (EBM) aims to combine the best available scientific evidence with clinical experience and individual judgment of patient needs. In the hierarchy of scientific evidence, systematic reviews (along with meta-analyses) occupy the highest levels in terms of the quality of evidence. A systematic review is the process of searching, selecting, appraising, synthesising and reporting clinical evidence on a particular question or topic. It is currently considered the best, least biased and most rational way to organise, gather, evaluate and integrate scientific evidence from the rapidly-changing medical and healthcare literature. Systematic reviews could be used to present current concepts or serve as review articles and replace the traditional expert opinion or narrative review. This article explains the structure and content of a systematic review.
Surveying trends in radiation oncology medical physics in the Asia Pacific Region

Kron T, Healy B, Ng KH

Phys Med, 2016 Jul;32(7):883-8.
PMID: 27320695 DOI: 10.1016/j.ejmp.2016.06.001

OBJECTIVE: Our study aims to assess and track work load, working conditions and professional recognition of radiation oncology medical physicists (ROMPs) in the Asia Pacific Region over time.
METHODS: A structured questionnaire was mailed in 2008, 2011 and 2014 to senior medical physicists representing 23 countries. The questionnaire covers 7 themes: education and training including certification; staffing; typical tasks; professional organisations; resources; research and teaching; job satisfaction.
RESULTS: Across all surveys the response rate was >85% with the replies representing practice affecting more than half of the world's population. The expectation of ROMP qualifications (MSc and between 1 and 3years of clinical experience) has not changed much over the years. However, compared to 2008, the number of medical physicists in many countries has doubled. Formal professional certification is only available in a small number of countries. The number of experienced ROMPs is small in particular in low and middle income countries. The increase in staff numbers from 2008 to 2014 is matched by a similar increase in the number of treatment units which is accompanied by an increase in treatment complexity. Many ROMPs are required to work overtime and not many find time for research. Resource availability has only improved marginally and ROMPs still feel generally overworked, but professional recognition, while varying widely, appears to be improving slowly.
CONCLUSION: While number of physicists and complexity of treatment techniques and technologies have increased significantly, ROMP practice remains essentially unchanged over the last 6years in the Asia Pacific Region.
Fulltext Therapeutic radionuclides in nuclear medicine: current and future prospects

Yeong CH, Cheng MH, Ng KH

J Zhejiang Univ Sci B, 2014 Oct;15(10):845-63.
PMID: 25294374 DOI: 10.1631/jzus.B1400131

The potential use of radionuclides in therapy has been recognized for many decades. A number of radionuclides, such as iodine-131 ((131)I), phosphorous-32 ((32)P), strontium-90 ((90)Sr), and yttrium-90 ((90)Y), have been used successfully for the treatment of many benign and malignant disorders. Recently, the rapid growth of this branch of nuclear medicine has been stimulated by the introduction of a number of new radionuclides and radiopharmaceuticals for the treatment of metastatic bone pain and neuroendocrine and other malignant or non-malignant tumours. Today, the field of radionuclide therapy is enjoying an exciting phase and is poised for greater growth and development in the coming years. For example, in Asia, the high prevalence of thyroid and liver diseases has prompted many novel developments and clinical trials using targeted radionuclide therapy. This paper reviews the characteristics and clinical applications of the commonly available therapeutic radionuclides, as well as the problems and issues involved in translating novel radionuclides into clinical therapies.
Intra-epithelially entrapped blood vessels in ameloblastoma

Siar CH, Ishak I, Ng KH

J Oral Pathol Med, 2015 May;44(5):378-85.
PMID: 25155411 DOI: 10.1111/jop.12247

The ameloblastoma is a benign but locally aggressive odontogenic neoplasm with a high recurrence rate. While significant progress has been made in our understanding regarding the role of tumoral vasculature relative to the diverse behavioral characteristics of this tumor, no attention has been paid to a distinct subset of blood vessels entrapped within its epithelial compartment. As vascular niches are known to influence tumoral growth, clarification of these vessels is important. The objectives of this study were to investigate the morphologic characteristics of intra-epithelially entrapped blood vessels (IEBVs) in ameloblastoma and to speculate on their relevance.
Podoplanin, E-cadherin, β-catenin, and CD44v6 in recurrent ameloblastoma: their distribution patterns and relevance

Siar CH, Ishak I, Ng KH

J Oral Pathol Med, 2015 Jan;44(1):51-8.
PMID: 25059841 DOI: 10.1111/jop.12203

Ameloblastoma is a benign but locally infiltrative odontogenic epithelial neoplasm with a high risk for recurrence. Podoplanin, a lymphatic endothelium marker, putatively promotes collective cell migration and invasiveness in this neoplasm. However, its role in the recurrent ameloblastoma (RA) remains unclear. As morphological, signaling, and genetic differences may exist between primary and recurrent tumors, clarification of their distribution patterns is of relevance.
Radiation dose in coronary CT angiography associated with prospective ECG-triggering technique: comparisons with different CT generations

Sabarudin A, Sun Z, Ng KH

Radiat Prot Dosimetry, 2013;154(3):301-7.
PMID: 22972797 DOI: 10.1093/rpd/ncs243

A retrospective analysis was performed in patients undergoing prospective ECG-triggered coronary computed tomography (CT) angiography (CCTA) with the single-source 64-slice CT (SSCT), dual-source 64-slice CT (DSCT), dual-source 128-slice CT and 320-slice CT with the aim of comparing the radiation dose associated with different CT generations. A total of 164 patients undergoing prospective ECG-triggered CCTA with different types of CT scanners were studied with the mean effective doses estimated at 6.8 ± 3.2, 4.2 ± 1.9, 4.1±0.6 and 3.8 ± 1.4 mSv corresponding to the 128-slice DSCT, 64-slice DSCT, 64-slice SSCT and 320-slice CT scanners. In this study a positive relationship was found between the effective dose and the body mass index (BMI). A low radiation dose is achieved in prospective ECG-triggered CCTA, regardless of the CT scanner generation. BMI is identified as the major factor that has a direct impact on the effective dose associated with prospective ECG-triggered CCTA.
Fulltext A hybrid distance measure for clustering expressed sequence tags originating from the same gene family

Ng KH, Ho CK, Phon-Amnuaisuk S

PLoS One, 2012;7(10):e47216.
PMID: 23071763 DOI: 10.1371/journal.pone.0047216

Clustering is a key step in the processing of Expressed Sequence Tags (ESTs). The primary goal of clustering is to put ESTs from the same transcript of a single gene into a unique cluster. Recent EST clustering algorithms mostly adopt the alignment-free distance measures, where they tend to yield acceptable clustering accuracies with reasonable computational time. Despite the fact that these clustering methods work satisfactorily on a majority of the EST datasets, they have a common weakness. They are prone to deliver unsatisfactory clustering results when dealing with ESTs from the genes derived from the same family. The root cause is the distance measures applied on them are not sensitive enough to separate these closely related genes.
Ameloblastoma of the jaws: a retrospective analysis of 340 cases in a Malaysian population

Siar CH, Lau SH, Ng KH

J Oral Maxillofac Surg, 2012 Mar;70(3):608-15.
PMID: 21723654 DOI: 10.1016/j.joms.2011.02.039

Ameloblastoma of the human jaw is an uncommon but clinically significant odontogenic epithelial neoplasm. The aim was to analyze the clinicopathologic characteristics of ameloblastoma in a Malaysian population.
Optimal beam quality selection based on contrast-to-noise ratio and mean glandular dose in digital mammography

Aminah M, Ng KH, Abdullah BJ, Jamal N

Australas Phys Eng Sci Med, 2010 Dec;33(4):329-34.
PMID: 20938762 DOI: 10.1007/s13246-010-0035-3

The performance of a digital mammography system (Siemens Mammomat Novation) using different target/filter combinations and tube voltage has been assessed. The objective of this study is to optimize beam quality selection based on contrast-to-noise ratio (CNR) and mean glandular dose (MGD). Three composition of breast were studied with composition of glandular/adipose of 30/70, 50/50, and 70/30. CNR was measured using 2, 4 and 6 cm-thick simulated breast phantoms with an aluminium sheet of 0.1 mm thickness placed on top of the phantom. Three target/filter combinations, namely molybdenum/molybdenum (Mo/Mo), molybdenum/rhodium (Mo/Rh) and tungsten/rhodium (W/Rh) with various tube voltage and mAs were tested. MGD was measured for each exposure. For 50/50 breast composition, Mo/Rh combination with tube voltage 26 kVp is optimal for 2 cm-thick breast. W/Rh combination with tube voltage 27 and 28 kVp are optimal for 4 and 6 cm-thick breast, respectively. For both 30/70 and 70/30 breast composition, W/Rh combination is optimal with tube voltage 25, 26 and 27 kVp, respectively. From our study it was shown that there are potential of dose reduction up to 11% for a set CNR of 3.0 by using beam quality other than that are determined by AEC selection. Under the constraint of lowest MGD, for a particular breast composition, calcification detection is optimized by using a softer X-ray beam for thin breast and harder X-ray beam for thick breast. These experimental results also indicate that for breast with high fibroglandular tissues (70/30), the use of higher beam quality does not always increase calcification detection due to additional structured noise caused by the fibroglandular tissues itself.
The characteristics of Fuji IP Cassette Type PII and application for radiation oncology quality assurance tests and portal imaging

Soh HS, Ung NM, Ng KH

Australas Phys Eng Sci Med, 2008 Jun;31(2):146-50.
PMID: 18697706

The advancement of digital imaging has prompted more medical institutions to go filmless. The computed radiography (CR) system is becoming an important tool not only in diagnostic imaging, but also in radiation oncology. A new CR system that was specially designed for the use in radiation oncology, Fuji IP cassette type PII has been introduced to the market in the middle of year 2006. This project aimed to study some basic physical characteristics of this new type of cassette and explore its application for performing quality assurance (QA) tests and portal imaging in radiotherapy. All the images were read by FCR 5000 Plus reader. The image was found to reach its saturation value of 1023 (due to the image was stored in 10 bits data) by depending on the sensitivity value being adjusted. The uniformity test gave the result of 0.12%. The cassette was used to perform the QA tests which were previously performed using film. All the results met the specification as stated in AAPM Task Group 40. The comparison for the portal images of PortalVision contrast-detail phantom showed that the spatial resolution of the images obtained by CR system (Fujifilm Co., Ltd., Tokyo, Japan) were better than the EPID (Varian Medical Systems, Inc., Palo Alto, USA) and film system (Eastman Kodak Co., New York, USA). The IP cassette type PII was found to be suitable as an alternative QA test tool and portal imaging in radiotherapy.
Fulltext Evaluation of radiation dose and image quality following changes to tube potential (kVp) in conventional paediatric chest radiography

Ramanaidu S, Sta Maria R, Ng Kh, George J, Kumar G

Biomed Imaging Interv J, 2006 Jul;2(3):e35.
PMID: 21614244 MyJurnal DOI: 10.2349/biij.2.3.e35

A study of radiation dose and image quality following changes to the tube potential (kVp) in paediatric chest radiography.
Fulltext Diffusion weighted MR imaging in acute vertebral compression fractures: differentiation between malignant and benign causes

Bhugaloo A, Abdullah B, Siow Y, Ng Kh

Biomed Imaging Interv J, 2006 Apr;2(2):e12.
PMID: 21614224 MyJurnal DOI: 10.2349/biij.2.2.e12

The primary objective of this study was to evaluate the specificity and sensitivity of diffusion weighted MR imaging (DWI) in the differentiation and characterisation between benign and malignant vertebral compression fractures compared with conventional T1 WI, T2 WI and fat suppressed contrast enhanced T1 WI in the Malaysian population.
Global quality control perspective for the physical and technical aspects of screen-film mammography--image quality and radiation dose

Ng KH, Jamal N, DeWerd L

Radiat Prot Dosimetry, 2006;121(4):445-51.
PMID: 16709704

The systematic monitoring of image quality and radiation dose is an ultimate solution to ensuring the continuously high quality of mammography examination. At present several protocols exist around the world, and different test objects are used for quality control (QC) of the physical and technical aspects of screen-film mammography. This situation may lead to differences in radiation image quality and dose reported. This article reviews the global QC perspective for the physical and technical aspects of screen-film mammography with regard to image quality and radiation dose. It points out issues that must be resolved in terms of radiation dose and that also affect the comparison.
Health beliefs in oral cancer: Malaysian estate Indian scenario

Tan BS, Ng KH, Esa R

Patient Educ Couns, 2001 Mar;42(3):205-11.
PMID: 11164319

This is a study to describe the health beliefs related to oral cancer (OC) in a high-risk group in Malaysia, a predominantly Indian community living in an agricultural setting called an estate. The study population was a convenient sample of 112 adults, above 20 years of age, attending oral cancer screening in two estates. The subjects consisted of 106 (94.6%) Indians and six (5.4%) Malays. Using the Health Belief Model, the perceptions of susceptibility to OC, its severity, and the benefits of and barriers to preventive actions, as well as beliefs underlying OC aetiology were investigated. About half of the subjects (n=57, 50.9%) felt susceptible to oral cancer. A majority of subjects (n=93, 83.0%) felt that oral cancer is a severe disease. Thirty four people (30.4%) perceived OC as a preventable disease, while 56 (50%) did not, and the remaining 22 (19.6%) did not know if OC was preventable or not. The majority of subjects (84.8%) believed that modifications to the betel quid habit could be beneficial. The information solicited can be used as a starting point to design health-education activities aimed at this group in particular and the population in general.
An in vitro study comparing two different film-screen combinations in the detection of impacted fish bones

Abdullah BJ, Kaur H, Ng KH

Br J Radiol, 1998 Sep;71(849):930-3.
PMID: 10195007

Dried fish bones from eight species of Malaysian fish were placed in an animal cadaver at four sites (tonsil, valleculae, larynx and oesophagus) and radiographed using a double and a single film-screen combination. The use of the single film-screen combination resulted in visibility of all fish bones placed in the larynx, two of which were not visible on the double film-screen combination. There was a 50% increase of the visibility of the fish bones in the oesophagus using the single film-screen combination. The difference in dose and cost between the two different film-screen combinations was not significant.
Evaluating the quality of images produced by soft X-ray units

Bradley DA, Wong CS, Ng KH

Appl Radiat Isot, 2000 9 26;53(4-5):691-7.
PMID: 11003508

For broad-beam soft X-ray sources, assessment of the quality of image produced by such units is made complex by the low penetration capabilities of the radiation. In the present study we have tested the utility of several types of test tool, some of which have been fabricated by us, as part of an effort to evaluate several key image defining parameters. These include the film characteristic, focal-spot size, image resolution and detail detectability. The two sources of X-rays used in present studies were the University of Malaya flash X-ray device (UMFX1) and a more conventional soft X-ray tube (Softex, Tokyo), the latter operating at peak accelerating potentials of 20 kVp. We have established, for thin objects, that both systems produce images of comparable quality and, in particular, objects can be resolved down to better than 45 microm.
Medical radiation exposures for diagnostic radiology in Malaysia

Ng KH, Abdullah BJ, Sivalingam S

Health Phys, 1999 Jul;77(1):33-6.
PMID: 10376539

The medical radiation usage for diagnostic radiology in Malaysia (a Level II country) for 1990-1994 is reported, enabling a comparison to be made for the first time with the United Nations Scientific Committee on the Effects of Atomic Radiation Report. In 1994, the number of physicians, radiologists, x-ray units, and x-ray examinations per 1,000 population was 0.45, 0.005, 0.065, and 183, respectively. (Level I countries had averages of 2.6, 0.072, 0.35, and 860, respectively). In 1994, a total of 3.6 million x-ray examinations were performed; the annual effective dose per capita to the population was 0.05 mSv, and the collective effective dose was 1,000 person-Sv. Chest examinations contributed 63% of the total. Almost all examinations experienced increasing frequency from 1990 to 1994 except for barium studies, cholecystography, and intravenous urography (-23%, -36%, -51%). These decreases are related to the increasing use of ultrasound and greater availability of fiberoptic endoscopy. Notable increases during the same period were observed in computed tomography (161%), cardiac procedures (190%), and mammography (240%). In order to progress from Level II to Level I status Malaysia needs to expand and upgrade radiological service in tandem with the health care development of the country.
Wavelet-based compression of medical images: filter-bank selection and evaluation

Saffor A, bin Ramli AR, Ng KH

Australas Phys Eng Sci Med, 2003 Jun;26(2):39-44.
PMID: 12956184

Wavelet-based image coding algorithms (lossy and lossless) use a fixed perfect reconstruction filter-bank built into the algorithm for coding and decoding of images. However, no systematic study has been performed to evaluate the coding performance of wavelet filters on medical images. We evaluated the best types of filters suitable for medical images in providing low bit rate and low computational complexity. In this study a variety of wavelet filters are used to compress and decompress computed tomography (CT) brain and abdomen images. We applied two-dimensional wavelet decomposition, quantization and reconstruction using several families of filter banks to a set of CT images. Discreet Wavelet Transform (DWT), which provides efficient framework of multi-resolution frequency was used. Compression was accomplished by applying threshold values to the wavelet coefficients. The statistical indices such as mean square error (MSE), maximum absolute error (MAE) and peak signal-to-noise ratio (PSNR) were used to quantify the effect of wavelet compression of selected images. The code was written using the wavelet and image processing toolbox of the MATLAB (version 6.1). This results show that no specific wavelet filter performs uniformly better than others except for the case of Daubechies and bi-orthogonal filters which are the best among all. MAE values achieved by these filters were 5 x 10(-14) to 12 x 10(-14) for both CT brain and abdomen images at different decomposition levels. This indicated that using these filters a very small error (approximately 7 x 10(-14)) can be achieved between original and the filtered image. The PSNR values obtained were higher for the brain than the abdomen images. For both the lossy and lossless compression, the 'most appropriate' wavelet filter should be chosen adaptively depending on the statistical properties of the image being coded to achieve higher compression ratio.
The World Wide Web is a net disservice to medical physicists in developing countries

Ng KH, Niroomand-Rad A, Hendee WR

Med Phys, 2001 Dec;28(12):2391-3.
PMID: 11797940
Mammographic image quality and exposure in South East Asia

Ng KH, DeWerd LA, Schmidt RC

Australas Phys Eng Sci Med, 2000 Dec;23(4):135-7.
PMID: 11376538

Generally there is a significant delay before optimized performance of mammography is fully realized in the developing countries. To evaluate the status of mammographic performance, a survey of mammographic image quality and exposure was performed in nine hospitals from four selected South East Asian countries. The entrance exposure on the surface of the American College of Radiology (ACR) mammographic phantom (ACR-RMI model 156) was made using both thermoluminescent dosimeters (TLDs) and an ionization chamber. The TLDs were mailed from the University of Wisconsin Radiation Calibration Laboratory (UWRCL) to the cooperating hospitals. The surveyed hospitals processed the images and returned them to the UWRCL for subsequent evaluation of the image quality of the mammographic phantom. Machine-specific data, technique factors and sensitometric data were also obtained. At 28 kVp, the mean entrance exposure is 0.91 R (0.46 to 2.6 R), mean glandular dose is 1.61 mGy (0.90 to 4.15 mGy), mean optical density is 1.37 (0.66 to 2.30), mean total phantom image score is 9.1(4-12). Only three of the nine hospitals tested achieved an acceptable score above the minimum 10. Results for 25 and 30 kVp showed similar trend. The variation between the ion chamber measurements and TLD measurements ranged from 4 to 24%. There is a wide variation in the image quality and entrance exposure among hospitals in South East Asia. There is a need for a quality assurance program. The factors that cause low score in the phantom images must be corrected. Calibration and the use of appropriate ionization chambers for mammography is important.

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