Displaying publications 1 - 20 of 35 in total

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  1. Kua Ch, Abdul Aziz Y
    Biomed Imaging Interv J, 2008 Oct;4(4):e24.
    PMID: 21611013 DOI: 10.2349/biij.4.4.e24
    Presence of air in the kidney can be problematic as the location of the air in different parts of the kidney greatly affects the subsequent management and outcome of the patient. We present here a case of a patient who had emphysematous pyelitis, in which CT scan was able to display presence of air only in the collecting system, thus differentiating this condition from the more fulminant emphysematous pyelonephritis. This leads to a more favourable prognosis and outcome to the patient.
  2. Lau S, Ng KH, Abdul Aziz YF
    Br J Radiol, 2016 Oct;89(1066):20160258.
    PMID: 27452264 DOI: 10.1259/bjr.20160258
    OBJECTIVE: To investigate the sensitivity and robustness of a volumetric breast density (VBD) measurement system to errors in the imaging physics parameters including compressed breast thickness (CBT), tube voltage (kVp), filter thickness, tube current-exposure time product (mAs), detector gain, detector offset and image noise.

    METHODS: 3317 raw digital mammograms were processed with Volpara(®) (Matakina Technology Ltd, Wellington, New Zealand) to obtain fibroglandular tissue volume (FGV), breast volume (BV) and VBD. Errors in parameters including CBT, kVp, filter thickness and mAs were simulated by varying them in the Digital Imaging and Communications in Medicine (DICOM) tags of the images up to ±10% of the original values. Errors in detector gain and offset were simulated by varying them in the Volpara configuration file up to ±10% from their default values. For image noise, Gaussian noise was generated and introduced into the original images.

    RESULTS: Errors in filter thickness, mAs, detector gain and offset had limited effects on FGV, BV and VBD. Significant effects in VBD were observed when CBT, kVp, detector offset and image noise were varied (p 

  3. Lau S, Abdul Aziz YF, Ng KH
    PLoS One, 2017;12(4):e0175781.
    PMID: 28419125 DOI: 10.1371/journal.pone.0175781
    OBJECTIVES: To investigate: (1) the variability of mammographic compression parameters amongst Asian women; and (2) the effects of reducing compression force on image quality and mean glandular dose (MGD) in Asian women based on phantom study.

    METHODS: We retrospectively collected 15818 raw digital mammograms from 3772 Asian women aged 35-80 years who underwent screening or diagnostic mammography between Jan 2012 and Dec 2014 at our center. The mammograms were processed using a volumetric breast density (VBD) measurement software (Volpara) to assess compression force, compression pressure, compressed breast thickness (CBT), breast volume, VBD and MGD against breast contact area. The effects of reducing compression force on image quality and MGD were also evaluated based on measurement obtained from 105 Asian women, as well as using the RMI156 Mammographic Accreditation Phantom and polymethyl methacrylate (PMMA) slabs.

    RESULTS: Compression force, compression pressure, CBT, breast volume, VBD and MGD correlated significantly with breast contact area (p<0.0001). Compression parameters including compression force, compression pressure, CBT and breast contact area were widely variable between [relative standard deviation (RSD)≥21.0%] and within (p<0.0001) Asian women. The median compression force should be about 8.1 daN compared to the current 12.0 daN. Decreasing compression force from 12.0 daN to 9.0 daN increased CBT by 3.3±1.4 mm, MGD by 6.2-11.0%, and caused no significant effects on image quality (p>0.05).

    CONCLUSIONS: Force-standardized protocol led to widely variable compression parameters in Asian women. Based on phantom study, it is feasible to reduce compression force up to 32.5% with minimal effects on image quality and MGD.

  4. Hashim H, Rahmat K, Abdul Aziz YF, Chandran PA
    Ear Nose Throat J, 2014 Jun;93(6):E20-3.
    PMID: 24932824
    We report the case of a 30-year-old woman who was referred to us for evaluation of a 2-week history of fever, headache, vomiting, bilateral ptosis, and blurred vision. Imaging obtained by the referring institution had identified a sphenoid sinus mass and diffuse meningeal infiltration, which was thought to represent an infective process. We subsequently identified the mass as a metastatic hepatocellular carcinoma (HCC). The patient was placed under palliative care, and she died 1 month later. Metastases to the sphenoid sinus from any primary source are very rare, and they are generally not considered in the radiologic differential diagnosis. HCC is known to metastasize to the lung, lymph nodes, and musculoskeletal system; again, reported cases of metastasis to the sphenoid sinus are rare. Indeed, our review of the English-language literature found only 6 previously reported cases of sinonasal metastasis of a primary HCC. A diagnosis of a sinonasal metastasis is more difficult in a patient who has no previous diagnosis of a primary malignancy. In presenting this case, our aim is to remind readers of this possibility.
  5. Chan RS, Abdul Aziz YF, Chandran P, Ng EK
    Singapore Med J, 2011 Nov;52(11):e232-5.
    PMID: 22173263
    A 62 year-old woman who presented with an atraumatic acute abdomen was discovered to have haemoperitoneum with splenic rupture on urgent computed tomography and was immediately referred for life-saving emergency splenectomy. Histopathological examination revealed secondary splenic amyloidosis. The patient was later found to be suffering from infective endocarditis secondary to her permanent cardiac pacemaker. This report describes a patient who could have suffered from a long-standing infected vegetation on a permanent cardiac pacemaker, which led to splenic amyloidosis and spontaneous splenic rupture.
  6. Kaur S, Rahmat K, Chandran PA, Alli K, Aziz YF
    Singapore Med J, 2012 Nov;53(11):e240-3.
    PMID: 23192514
    The incidence of synchronous bilateral infiltrating breast cancer has been reported to be 2%. However, synchronous unilateral infiltrating ductal carcinoma and infiltrating lobular carcinoma (ILC) are very rarely reported. We present a woman with palpable ILC who was later found to have synchronous well-circumscribed ductal carcinoma on further imaging. We also discuss the use of diagnostic approaches such as ultrasonography, mammography and histopathology. This case highlights the importance of careful assessment of concurrent lesions in the breast in the presence of an existing carcinoma.
  7. Abdullah BJ, Mohammad N, Sangkar JV, Abd Aziz YF, Gan GG, Goh KY, et al.
    Br J Radiol, 2005 Jul;78(931):596-600.
    PMID: 15961840
    The objective of this study was to prospectively determine the incidence of venous thrombosis (VT) in the upper limbs in patients with peripherally inserted central catheters (PICC). We prospectively investigated the incidence of VT in the upper limbs of 26 patients who had PICC inserted. The inclusion criteria were all patients who had a PICC inserted, whilst the exclusion criterion was the inability to perform a venogram (allergies, previous contrast medium reaction and inability of gaining venous access). Both valved and non-valved catheters were evaluated. Prior to removal of the PICC, an upper limb venogram was performed. The number of segments involved with VT were determined. The duration of central venous catheterization was classified as; less than 6 days, between 6 days and 14 days and more than 14 days. VT was confirmed in 38.5% (10/26) of the patients. The majority 85.7% (12/14) were complete occlusive thrombi and the majority of VT only involved one segment. There was no statistical correlation between the site of insertion of the PICC and the location of VT. Neither was there any observed correlation between the occurrence of VT with the patient's history of hypertension, hypercholesterolaemia, coronary artery disease, diabetes mellitus, cardiac insufficiency, smoking or cancer. There was also no statistical correlation with the size of the catheter. In conclusion, PICCs are associated with a significant risk of upper extremity deep vein thrombosis (UEVT).
  8. Johari B, Abdul Aziz YF, Krishnasamy S, Looi LM, Hashim SA, Raja Mokhtar RA
    Iran J Radiol, 2015 Apr;12(2):e11197.
    PMID: 26060549 DOI: 10.5812/iranjradiol.11197
    The presence of tumor thrombus in the right atrium is frequently the result of direct intraluminal extension of infra-diaphragmatic malignancy into the inferior vena cava (IVC) or supradiaphragmatic carcinoma into the superior vena cava (SVC). Right atrial tumor thrombus with extension into both SVC and IVC has not been reported in the literature. We present a patient who presented with symptoms of right atrial and SVC obstruction. Imaging revealed presence of a thrombus in the right atrium, extending to the SVC and IVC, with the additional findings of a left adrenal mass and multiple liver lesions. The histopathological examination of the right atrial mass revealed metastatic adenocarcinoma cells. The patient was given a presumptive diagnosis of metastatic adenocarcinoma, most likely adrenal in origin, with multiple hepatic lesions suspicious for metastasis. The clinical outcome of the patient was not favorable; the patient succumbed before the adrenal mass could be confirmed to be the primary tumor. This case highlights that in patients manifesting with extensive cavoatrial thrombus as, the existence of primary carcinoma should be considered especially in the adrenal cortex or in the lung.
  9. Sze TL, Abdul Aziz YF, Abu Bakar N, Mohd Sani F, Oemar H
    Iran J Radiol, 2015 Jan;12(1):e6878.
    PMID: 25793089 DOI: 10.5812/iranjradiol.6878
    Coronary artery fistula (CAF) is a rare anomaly of the coronary artery. Patients with this condition are usually asymptomatic. However, cardiac failure may occur later in life due to progressive enlargement of the fistula. Diagnosis is traditionally made by echocardiogram and conventional angiogram. However with the advantage of new technologies such as computed tomography (CT) coronary angiography, the course and communications of these fistulae can be delineated non-invasively and with greater accuracy. We report a case of a left circumflex artery fistula to the coronary sinus which was suspected on echocardiogram and the diagnosis was clinched on ECG-gated CT.
  10. Leong CO, Liew YM, Bilgen M, Abdul Aziz YF, Chee KH, Chiam YK, et al.
    J Magn Reson Imaging, 2016 Jul 15.
    PMID: 27418150 DOI: 10.1002/jmri.25390
    To propose a cardiac motion tracking model that evaluates wall motion abnormality in postmyocardial infarction patients. Correlation between the motion parameter of the model and left ventricle (LV) function was also determined.
  11. Khalid A, Lim E, Chan BT, Abdul Aziz YF, Chee KH, Yap HJ, et al.
    J Magn Reson Imaging, 2019 04;49(4):1006-1019.
    PMID: 30211445 DOI: 10.1002/jmri.26302
    BACKGROUND: Existing clinical diagnostic and assessment methods could be improved to facilitate early detection and treatment of cardiac dysfunction associated with acute myocardial infarction (AMI) to reduce morbidity and mortality.

    PURPOSE: To develop 3D personalized left ventricular (LV) models and thickening assessment framework for assessing regional wall thickening dysfunction and dyssynchrony in AMI patients.

    STUDY TYPE: Retrospective study, diagnostic accuracy.

    SUBJECTS: Forty-four subjects consisting of 15 healthy subjects and 29 AMI patients.

    FIELD STRENGTH/SEQUENCE: 1.5T/steady-state free precession cine MRI scans; LGE MRI scans.

    ASSESSMENT: Quantitative thickening measurements across all cardiac phases were correlated and validated against clinical evaluation of infarct transmurality by an experienced cardiac radiologist based on the American Heart Association (AHA) 17-segment model.

    STATISTICAL TEST: Nonparametric 2-k related sample-based Kruskal-Wallis test; Mann-Whitney U-test; Pearson's correlation coefficient.

    RESULTS: Healthy LV wall segments undergo significant wall thickening (P 50% transmurality) underwent remarkable wall thinning during contraction (thickening index [TI] = 1.46 ± 0.26 mm) as opposed to healthy myocardium (TI = 4.01 ± 1.04 mm). For AMI patients, LV that showed signs of thinning were found to be associated with a significantly higher percentage of dyssynchrony as compared with healthy subjects (dyssynchrony index [DI] = 15.0 ± 5.0% vs. 7.5 ± 2.0%, P 

  12. Tan LK, Liew YM, Lim E, Abdul Aziz YF, Chee KH, McLaughlin RA
    Med Biol Eng Comput, 2018 Jun;56(6):1053-1062.
    PMID: 29147835 DOI: 10.1007/s11517-017-1750-7
    In this paper, we develop and validate an open source, fully automatic algorithm to localize the left ventricular (LV) blood pool centroid in short axis cardiac cine MR images, enabling follow-on automated LV segmentation algorithms. The algorithm comprises four steps: (i) quantify motion to determine an initial region of interest surrounding the heart, (ii) identify potential 2D objects of interest using an intensity-based segmentation, (iii) assess contraction/expansion, circularity, and proximity to lung tissue to score all objects of interest in terms of their likelihood of constituting part of the LV, and (iv) aggregate the objects into connected groups and construct the final LV blood pool volume and centroid. This algorithm was tested against 1140 datasets from the Kaggle Second Annual Data Science Bowl, as well as 45 datasets from the STACOM 2009 Cardiac MR Left Ventricle Segmentation Challenge. Correct LV localization was confirmed in 97.3% of the datasets. The mean absolute error between the gold standard and localization centroids was 2.8 to 4.7 mm, or 12 to 22% of the average endocardial radius. Graphical abstract Fully automated localization of the left ventricular blood pool in short axis cardiac cine MR images.
  13. Tan LK, McLaughlin RA, Lim E, Abdul Aziz YF, Liew YM
    J Magn Reson Imaging, 2018 07;48(1):140-152.
    PMID: 29316024 DOI: 10.1002/jmri.25932
    BACKGROUND: Left ventricle (LV) structure and functions are the primary assessment performed in most clinical cardiac MRI protocols. Fully automated LV segmentation might improve the efficiency and reproducibility of clinical assessment.

    PURPOSE: To develop and validate a fully automated neural network regression-based algorithm for segmentation of the LV in cardiac MRI, with full coverage from apex to base across all cardiac phases, utilizing both short axis (SA) and long axis (LA) scans.

    STUDY TYPE: Cross-sectional survey; diagnostic accuracy.

    SUBJECTS: In all, 200 subjects with coronary artery diseases and regional wall motion abnormalities from the public 2011 Left Ventricle Segmentation Challenge (LVSC) database; 1140 subjects with a mix of normal and abnormal cardiac functions from the public Kaggle Second Annual Data Science Bowl database.

    FIELD STRENGTH/SEQUENCE: 1.5T, steady-state free precession.

    ASSESSMENT: Reference standard data generated by experienced cardiac radiologists. Quantitative measurement and comparison via Jaccard and Dice index, modified Hausdorff distance (MHD), and blood volume.

    STATISTICAL TESTS: Paired t-tests compared to previous work.

    RESULTS: Tested against the LVSC database, we obtained 0.77 ± 0.11 (Jaccard index) and 1.33 ± 0.71 mm (MHD), both metrics demonstrating statistically significant improvement (P < 0.001) compared to previous work. Tested against the Kaggle database, the signed difference in evaluated blood volume was +7.2 ± 13.0 mL and -19.8 ± 18.8 mL for the end-systolic (ES) and end-diastolic (ED) phases, respectively, with a statistically significant improvement (P < 0.001) for the ED phase.

    DATA CONCLUSION: A fully automated LV segmentation algorithm was developed and validated against a diverse set of cardiac cine MRI data sourced from multiple imaging centers and scanner types. The strong performance overall is suggestive of practical clinical utility.

    LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018.

  14. Tan SK, Yeong CH, Ng KH, Abdul Aziz YF, Sun Z
    PLoS One, 2016;11(8):e0161543.
    PMID: 27552224 DOI: 10.1371/journal.pone.0161543
    OBJECTIVES: This study aimed to measure the absorbed doses in selected organs for prospectively ECG-triggered coronary computed tomography angiography (CCTA) using five different generations CT scanners in a female adult anthropomorphic phantom and to estimate the effective dose (HE).

    MATERIALS AND METHODS: Prospectively ECG-triggered CCTA was performed using five commercially available CT scanners: 64-detector-row single source CT (SSCT), 2 × 32-detector-row-dual source CT (DSCT), 2 × 64-detector-row DSCT and 320-detector-row SSCT scanners. Absorbed doses were measured in 34 organs using pre-calibrated optically stimulated luminescence dosimeters (OSLDs) placed inside a standard female adult anthropomorphic phantom. HE was calculated from the measured organ doses and compared to the HE derived from the air kerma-length product (PKL) using the conversion coefficient of 0.014 mSv∙mGy-1∙cm-1 for the chest region.

    RESULTS: Both breasts and lungs received the highest radiation dose during CCTA examination. The highest HE was received from 2 × 32-detector-row DSCT scanner (6.06 ± 0.72 mSv), followed by 64-detector-row SSCT (5.60 ± 0.68 and 5.02 ± 0.73 mSv), 2 × 64-detector-row DSCT (1.88 ± 0.25 mSv) and 320-detector-row SSCT (1.34 ± 0.48 mSv) scanners. HE calculated from the measured organ doses were about 38 to 53% higher than the HE derived from the PKL-to-HE conversion factor.

    CONCLUSION: The radiation doses received from a prospectively ECG-triggered CCTA are relatively small and are depending on the scanner technology and imaging protocols. HE as low as 1.34 and 1.88 mSv can be achieved in prospectively ECG-triggered CCTA using 320-detector-row SSCT and 2 × 64-detector-row DSCT scanners.

  15. Sim JH, Abdul Aziz YF, Mansor A, Vijayananthan A, Foong CC, Vadivelu J
    Med Educ Online, 2015;20:26185.
    PMID: 25697602 DOI: 10.3402/meo.v20.26185
    INTRODUCTION: The purpose of this study was to compare students' performance in the different clinical skills (CSs) assessed in the objective structured clinical examination.

    METHODS: Data for this study were obtained from final year medical students' exit examination (n=185). Retrospective analysis of data was conducted using SPSS. Means for the six CSs assessed across the 16 stations were computed and compared.

    RESULTS: Means for history taking, physical examination, communication skills, clinical reasoning skills (CRSs), procedural skills (PSs), and professionalism were 6.25±1.29, 6.39±1.36, 6.34±0.98, 5.86±0.99, 6.59±1.08, and 6.28±1.02, respectively. Repeated measures ANOVA showed there was a significant difference in the means of the six CSs assessed [F(2.980, 548.332)=20.253, p<0.001]. Pairwise multiple comparisons revealed significant differences between the means of the eight pairs of CSs assessed, at p<0.05.

    CONCLUSIONS: CRSs appeared to be the weakest while PSs were the strongest, among the six CSs assessed. Students' unsatisfactory performance in CRS needs to be addressed as CRS is one of the core competencies in medical education and a critical skill to be acquired by medical students before entering the workplace. Despite its challenges, students must learn the skills of clinical reasoning, while clinical teachers should facilitate the clinical reasoning process and guide students' clinical reasoning development.

  16. Teng ZS, Ser GTZ, Hong WH, Teo CH, Abdul Aziz YF, Vadivelu J, et al.
    Hum Resour Health, 2024 Aug 22;22(1):59.
    PMID: 39174962 DOI: 10.1186/s12960-024-00939-4
    BACKGROUND: In recent years, there have been many instances of negative sentiments expressed by and resignations observed from doctors working in the Ministry of Health (MOH), Malaysia. However, little is known about the perspectives of medical students and their career intentions. This study aims to determine the current Malaysian medical students' career intentions immediately after graduation and upon completing the 2 years of housemanship and to establish the factors influencing these intentions.

    METHODS: This was a cross-sectional study of 859 Malaysian medical students from 21 medical schools who voluntarily completed a self-administered online questionnaire that was disseminated by representatives from medical schools nationwide and social media platforms of a national medical student society.

    RESULTS: 37.8% of the respondents were optimistic about a career with the Ministry of Health (MOH), Malaysia in the future. Most of the respondents (91.2%) plan to join and complete the MOH Housemanship programme as soon as possible after graduation, with the majority of them (66.2%) planning to complete it in their state of origin. After 2 years of Housemanship programme, only more than half of the respondents (63.1%) plan to continue their careers in MOH. Slightly more than a quarter (27.1%) of the total respondents plan to emigrate to practise medicine, with 80.7% of them planning to return to Malaysia to practise medicine after some years or after completing specialisation training. Combining the career intentions of Malaysian medical students immediately after graduation and upon completion of the 2 years housemanship programme, only a slight majority (57.5%) of the respondents plan to continue their career in MOH eventually. Most of the respondents (85.0%) intend to specialise.

    CONCLUSION: A concerning number of Malaysian medical students plan to leave the Ministry of Health workforce, the main healthcare provider in Malaysia, in the future. Urgent government interventions are needed to address the underlying factors contributing to the potential exodus of future doctors to prevent further straining of the already overburdened healthcare system, posing a significant threat to public well-being. An annual national study to track medical students' career intentions is recommended to gather crucial data for the human resources for health planning in Malaysia.

  17. Chan BT, Abu Osman NA, Lim E, Chee KH, Abdul Aziz YF, Abed AA, et al.
    PLoS One, 2013;8(6):e67097.
    PMID: 23825628 DOI: 10.1371/journal.pone.0067097
    Dilated cardiomyopathy (DCM) is the most common myocardial disease. It not only leads to systolic dysfunction but also diastolic deficiency. We sought to investigate the effect of idiopathic and ischemic DCM on the intraventricular fluid dynamics and myocardial wall mechanics using a 2D axisymmetrical fluid structure interaction model. In addition, we also studied the individual effect of parameters related to DCM, i.e. peak E-wave velocity, end systolic volume, wall compliance and sphericity index on several important fluid dynamics and myocardial wall mechanics variables during ventricular filling. Intraventricular fluid dynamics and myocardial wall deformation are significantly impaired under DCM conditions, being demonstrated by low vortex intensity, low flow propagation velocity, low intraventricular pressure difference (IVPD) and strain rates, and high-end diastolic pressure and wall stress. Our sensitivity analysis results showed that flow propagation velocity substantially decreases with an increase in wall stiffness, and is relatively independent of preload at low-peak E-wave velocity. Early IVPD is mainly affected by the rate of change of the early filling velocity and end systolic volume which changes the ventriculo:annular ratio. Regional strain rate, on the other hand, is significantly correlated with regional stiffness, and therefore forms a useful indicator for myocardial regional ischemia. The sensitivity analysis results enhance our understanding of the mechanisms leading to clinically observable changes in patients with DCM.
  18. Tan SL, Rahmat K, Rozalli FI, Mohd-Shah MN, Aziz YF, Yip CH, et al.
    Clin Radiol, 2014 Jan;69(1):63-71.
    PMID: 24156797 DOI: 10.1016/j.crad.2013.08.007
    To investigate the capability and diagnostic accuracy of diffusion-weighted imaging (DWI) in differentiating benign from malignant breast lesions using 3 T magnetic resonance imaging (MRI).
  19. Suppiah S, Rahmat K, Mohd-Shah MN, Azlan CA, Tan LK, Aziz YF, et al.
    Clin Radiol, 2013 Sep;68(9):e502-10.
    PMID: 23706826 DOI: 10.1016/j.crad.2013.04.002
    To investigate the diagnostic accuracy of single-voxel proton magnetic resonance spectroscopy (SV (1)H MRS) by quantifying total choline-containing compounds (tCho) in differentiating malignant from benign lesions, and subsequently, to analyse the relationship of tCho levels in malignant breast lesions with their histopathological subtypes.
  20. Abu Bakar N, Abdul Aziz YF, Singh Sandhu R, Fadzli F, Yaakub NA, Krishnasamy S, et al.
    Heart Lung Circ, 2013 Apr;22(4):305-8.
    PMID: 22921797 DOI: 10.1016/j.hlc.2012.07.016
    Pericardial cysts are uncommon mediastinal lesions that are usually congenital in origin. Patients are usually asymptomatic and the cysts are generally discovered on routine radiography for unrelated purposes. This case illustrates a symptomatic presentation of a haemorrhagic pericardial cyst in which radiographic, echocardiographic and multislice (MRI and CT) imaging were performed. The imaging findings were not typical of pericardial cysts leading to a diagnostic quandary despite the varied imaging techniques. In conclusion, it is important to appreciate that the imaging findings of pericardial cysts can be varied. Radiologists and clinicians alike should be aware of this variability.
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