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B S Tan

Publications and source records attributed to B S Tan.

At least 19 recordsLinked to original sources
PubMed2006

High-average-power mid-infrared ZnGeP2 optical parametric oscillator with a wavelength-dependent polarization rotator.

A wavelength-dependent polarization rotator is used to transform the orthogonal polarizations of the signal and idler of a near-degenerate type II KTP optical parametric oscillator (OPO) into a common polarization state. This common polarization allows a single ZnGeP2 OPO to fully utilize the 2 microm signal and idler KTP OPO outputs in a mid-IR conversion. The simple design of the wavelength-dependent polarization rotator yields a compact source that simultaneously generates four mid-JR wavelengths collinearly with a total mid-IR average power of 5.5 W at a >15 kHz pulse repetition rate.

Journal Article↗
PubMed2005

Uterine artery embolisation for symptomatic fibroids in a tertiary hospital in Singapore.

INTRODUCTION: Transcatheter uterine artery embolisation (UAE) for the treatment of symptomatic uterine enlargement due to fibroids has been performed in several overseas centres with promising results. We report our experience with UAE in Singapore General Hospital. MATERIALS AND METHODS: Twenty women with symptomatic uterine fibroids who declined surgery were treated by transcatheter UAE. The uterine arteries were selectively catheterised and embolised with polyvinyl alcohol particles. Post-procedure analgesia was administered via a patient-controlled analgesia pump. The patients were followed up at regular intervals clinically and with transabdominal ultrasonography. RESULTS: Transcatheter UAE was performed on all patients with no major complications. Nineteen patients had both uterine arteries embolised while 1 patient had only the right uterine artery embolised on account of hypoplasia of the left uterine artery. The mean hospital stay was 3.5 days (range, 2 to 9). At a mean follow-up of 56 weeks (range, 6 to 168), all patients reported improvements in their presenting symptoms. Objective improvement in terms of reduction of uterine and fibroid sizes was determined on ultrasonography. The median size of the uterine volume decreased from 308 to 187 mL while the median diameter of the largest fibroid reduced from 6.2 to 4.6 cm. The median haemoglobin level increased to 12.7 g/dL from the pre-procedural median of 9.9 g/dL. One patient, who initially responded with a decrease in uterine and dominant fibroid size, became symptomatic (menorrhagia) at 6 months post-embolisation. She underwent a repeat procedure with complete resolution of symptoms. A second patient had recurrence of symptoms at 12 months, but was subsequently lost to follow-up. CONCLUSION: Mid-term results of UAE for the treatment of symptomatic fibroids in our hospital indicate this to be a safe and effective therapeutic option.

Adult↗
PubMed2005

Fluorosis prevalence among schoolchildren in a fluoridated community in Malaysia.

OBJECTIVES: This study aims to assess the magnitude of the problem of fluorosis among 10-11 year old schoolchildren in a fluoridated area in Malaysia. METHODS: An analytical cross-sectional design was adopted. Sampling of subjects was by a 2-stage systematic random sampling technique in Selangor, a fully fluoridated area. 1,343 10-11 year olds were assessed for fluorosis using the Dean's index. RESULTS: The prevalence of fluorosis was 58.7% (788 subjects); 478 (35.6%) subjects exhibited very mild fluorosis, 196 (14.6%) mild, 102 (7.6%) moderate, 12 (0.9%) severe and 555 (41.3%) no fluorosis. Tooth prevalence was 30.1%. Overall, the Community Fluorosis Index (CFI) was 0.96 and ranged from 0.23 to 1.72. Fifteen out of 30 schools had CFI > 1.0 (medium public health significance). CONCLUSIONS: The prevalence of dental fluorosis in Malaysia (mostly very mild to mild) at 58.7% is indicative of slightly above optimal levels of exposure. There were pockets of areas where fluorosis were of medium public health significance (CFI > 1.0). It must be cautioned that, fluorosis if not monitored closely, can become an increasing public health concern.

Child↗
PubMed2003

Clinical utility of selective intra-arterial calcium-stimulated hepatic venous sampling in regionalisation of insulinomas--the Singapore experience.

INTRODUCTION: To evaluate the efficacy and safety of selective intra-arterial calcium-stimulated hepatic venous sampling (ASVS) as a preoperative regionalisation modality for insulinomas. DESIGN AND METHODS: Four patients with biochemically-proven endogenous hyperinsulinism and negative spiral computed tomographic (CT) pancreas were subjected to ASVS between October 1999 to May 2001. Results obtained from ASVS were compared with localisation studies using either magnetic resonance imaging (MRI) or endoscopic ultrasonography (EUS); and these were confirmed surgically whenever possible. RESULTS: ASVS led to a definitive regionalisation in all 4 patients evaluated; the predicted location of the insulinoma matched the findings intraoperatively in all 3 patients who were operated upon. These were all proven to be insulinoma histologically. However, 1 patient showed a positive ASVS result in samples obtained from the left hepatic vein only. In the patient who was unable to undergo surgical resection due to other co-morbid factors, his ASVS findings were corroborated by localisation obtained from the MRI study. Conversely, EUS was found to give an incorrect localisation of insulinoma in 1 patient. Adverse effects were encountered in 3 patients (2 with mild hypotension and 1 with transient atrial fibrillation); however, premature termination of the procedure was not necessary in any of the patients. CONCLUSION: ASVS is accurate and reliable for regionalisation of insulinoma, especially in patients who do not have an obvious, unequivocal tumour using high quality current-generation MRI scans.

Adult↗
PubMed2003

Colorectal hepatic metastases: Role of radiofrequency ablation.

INTRODUCTION: Radiofrequency ablation (RFA) is a new minimally invasive treatment that has been increasingly used in the treatment of liver metastases. This review aims to outline the principles governing the use of RFA and to examine its role when applied to the management of colorectal liver metastases. METHODS: A Medline search of experimental and clinical studies relating to the use of RFA in the management of colorectal hepatic metastasis was carried out. RESULTS: RFA is currently used as an alternative to surgery in patients with unresectable disease, and sometimes as its companion, allowing patients hitherto considered unsuitable for resection to become surgical candidates. RFA has been shown to be safe and well tolerated, with few major complications and minimal patient discomfort. Although its use is unlikely to achieve cure in such patients, it has a definite role in palliation and relief of symptoms. Long-term data, when these become available, may also show improved survival. However, because RFA is a local ablative therapy, it does not address the progressive and systemic nature of colorectal carcinoma. CONCLUSIONS: RFA is an important alternative/complimentary tool in the management of colorectal hepatic metastases. Combining RFA with surgery or chemotherapy may reduce the incidence of local and systemic relapse.

Catheter Ablation↗
PubMed2003

Pregnancy following embolisation of uterine arteriovenous malformation--a case report.

INTRODUCTION: Pregnancy following successful embolisation of a uterine arteriovenous malformation (AVM) is rare. Hypovascularity of treated areas affecting placentation and fetal growth has been postulated to be the cause for adverse pregnancy outcomes. CLINICAL PICTURE: A 37-year-old multiparous lady presented with anaemia from repeated heavy vaginal bleeding from an iatrogenic uterine AVM. This was diagnosed with power Doppler ultrasonography and embolised after pelvis angiography with hystoacryl and lipiodol. Following this she had a spontaneous pregnancy with a normal outcome. CONCLUSION: There are no distinguishing clinical features of a uterine AVM. An index of suspicion and power Doppler sonography help in reaching a diagnosis. Dilatation and curettage should be avoided as this can precipitate torrential vaginal bleeding.

Adult↗
PubMed2002

Outcome of percutaneous nephrostomy for the management of pyonephrosis.

OBJECTIVE: The aim of this study was to evaluate the efficacy of percutaneous nephrostomy (PCN) drainage for the interim management of pyonephrosis. METHODS: Ninety-two consecutive patients [29 men, 63 women; mean age, 57 years; range, 23 to 88] who underwent PCN for the treatment of pyonephrosis from 1996 to 1999 were evaluated retrospectively. The clinical presentation, bacteriology and patient outcomes were analyzed. RESULTS: The majority [77%] of patients had underlying obstructing urinary calculi. Other causes of obstruction included strictures [9%], papillary necrosis [7%], pelvi-ureteric junction obstruction [4%] and malignant stricture [3%]. The microorganisms cultured were Escherichia coli [30%], Klebsiella [19%], Proteus [8%], Pseudomonas [5%], Enterococcus [5%], and Candida spp [5%]. The microorganisms were sensitive to gentamicin [79%], ceftriaxone [71%], cephalexin [54%], nitrofurantoin [40%], cotrimoxazole [35%], nalidixic acid [32%] and ampicillin [29%]. Only 30% of bladder urine cultures were positive for microorganisms; the addition of PCN cultures improved this yield to 58%. The antibiotic regimen was revised according to the PCN culture whenever there was a discrepancy. After PCN, 69% of patients underwent minimally invasive procedures as definitive treatment of the obstructing lesion. Only 14% of patients required open surgery. There was low procedure-related morbidity [14%] and low overall mortality [2%]. CONCLUSIONS: PCN cultures yield important bacteriological information. The procedure is associated with minimal morbidity, facilitates definitive treatment and provides therapeutic benefit.

Adult↗
PubMed2002

Single centre review of radiologically-guided percutaneous nephrostomies: a report of 273 procedures.

INTRODUCTION: To evaluate the technical success and complications associated with radiologically-guided percutaneous nephrostomies (PCNs) in a single centre. MATERIALS AND METHODS: A total of 273 PCNs performed in 190 patients in our hospital over a 3-year period from January 1997 to December 1999 were retrospectively reviewed. The study population consisted of 97 males and 93 females, ranging in age from 13 to 91 years. The main indications were urinary obstruction (77.7%), pyonephrosis (18.3%) and urinary diversion (4%). Demographic variables, technical and risk factors related to the procedure, complications, effect on urine cultures and body temperature; and subsequent patient management were examined. RESULTS: The technical success rate was 99%. The 30-day mortality was 7.2%, none of which were procedure related. Haemorrhage requiring transfusion occurred in 4.3% while septicaemia affected 3.2% of patients. Drainage catheter complications included catheter dislodgement and blockage which were 11.9% and 4.1%, respectively. Thirty-one per cent of PCNs subsequently underwent ureteric stenting as the definitive treatment modality. CONCLUSION: Radiologically-guided PCN is a safe procedure with a high technical success rate.

Adolescent↗
PubMed2002

A case of uterine artery pseudoaneurysms.

Uterine artery pseudoaneurysms is a rare cause of haemorrhage but is potentially life-threatening and can occur after common gynaecological operations such as a Caesarean section or a hysterectomy. A 33-year-old woman who developed secondary postpartum haemorrhage after a Caesarean section was diagnosed to have uterine artery pseudoaneurysms on ultrasound scan. She was treated with bilateral uterine artery embolisation via selective catherisation of uterine arteries. Good outcome with the aneurysms remaining obliterated was obtained. Angiographic embolisation is a safe and effective method of treating postpartum haemorrhage in haemodynamically stable patients and should be an option before resorting to surgery in appropriately selected cases.

Adult↗
PubMed2001

Health beliefs in oral cancer: Malaysian estate Indian scenario.

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.

Adult↗
PubMed2001

Diagnostic accuracy of focused appendiceal CT in clinically equivocal cases of acute appendicitis.

PURPOSE: To determine the diagnostic accuracy of modified focused appendiceal computed tomography (CT) to exclude or confirm appendicitis in patients who presented with equivocal symptoms and signs of appendicitis. MATERIALS AND METHODS: One hundred patients (age range, 14-81 years; mean age, 30.6 years) with equivocal symptoms and signs of acute appendicitis were included in this prospective study. Patients were given 30 mL of diatrizoate meglumine and diatrizoate sodium and 60 mL of sorbitol mixed in 1 L of water orally over 1 hour. CT was performed 1.5 hours after the commencement of oral contrast material administration. The criteria used for the diagnosis of appendicitis were (a) appendix greater than 6 mm in maximum diameter, (b) no contrast material in the appendiceal lumen, and (c) inflammatory changes in the periappendiceal fat. CT results were compared with histopathologic findings at appendectomy. Patients with negative CT findings were followed up by telephone or clinically. RESULTS: Of 100 cases, 30 were positive at CT and 70 were negative. There were 28 true-positive cases; two false-positive cases, one cecal diverticulitis and one pelvic peritonitis with periappendicitis; and two false-negative cases, one perforated appendix and one mucosal and submucosal inflammation of the appendix but no transmural inflammation. Sensitivity was 93%, specificity was 97%, and accuracy was 96%. CONCLUSION: Focused appendiceal CT in which oral contrast material is used alone yields high levels of accuracy in clinically equivocal cases of acute appendicitis.

Acute Disease↗
PubMed2001

188rhenium-TDD-lipiodol in treatment of inoperable primary hepatocellular carcinoma--a case report.

INTRODUCTION: The aim of this study was to investigate the potential of using 188Re Lipiodol for selective internal radiation therapy of inoperable hepatocellular carcinoma (HCC). CLINICAL PICTURE: A 33-year-old female with poorly-differentiated multicentric HCC, elevated alpha-fetoprotein (AFP) and increased serum alkaline phosphatase. TREATMENT: Over a 2-month interval, the patient was treated twice with 4GBq of 188Re-TDD-Lipiodol. OUTCOMES: There was good localisation of 188Re Lipiodol in the tumours, but also in thyroid (first treatment) and gastrointestinal tract (both treatments). So far (5 months post-treatment), the patient remains well with stable disease. CONCLUSIONS: 188Re Lipiodol can be an effective radiopharmaceutical for the treatment of HCC; however, more work must be done to minimise the uptake in bowel.

Adult↗
PubMed2001

Acute renal colic: value of unenhanced spiral computed tomography compared with intravenous urography.

OBJECTIVE: The objective of this study was to compare the efficacy of plain spiral computed tomographic (CT) scan with intravenous urography (IVU) in the evaluation of patients with suspected urinary calculi/obstruction. MATERIALS AND METHODS: Twenty consecutive patients with acute signs of renal colic were prospectively examined with unenhanced spiral CT followed by an IVU within the same day. The CT scans were reviewed jointly by 2 radiologists blinded to the IVU and a consensus was reached for each finding. The IVU was similarly reviewed by another 2 separate radiologists. RESULTS: Eleven of the 20 patients had signs of urinary obstruction on CT and IVU. Of these 11 patients, 7 had a ureteric calculus that was demonstrated on CT and IVU and 4 had a calculus that was demonstrated on CT only. Two patients had a urinary calculus seen on CT and IVU with no signs of urinary obstruction. One patient had a calculus seen on CT alone with no urinary obstruction. Two patients only had signs of urinary obstruction on CT. The remaining 4 cases had normal findings on CT and IVU. CONCLUSION: Unenhanced CT is more effective than IVU in identifying ureteric calculi and is equally effective in detecting urinary obstruction. CT is also useful in detecting secondary signs of obstruction even in the absence of any calculus.

Acute Disease↗
PubMed2000

Cold sweats.

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Adult↗
PubMed2000

DNA testing for fragile X syndrome in 255 males from special schools in Singapore.

INTRODUCTION: Fragile X syndrome, the most common cause of inherited mental retardation, results from unstable expansion of a trinucleotide (CGG)n repeat in the FMR1 gene. Phenotypic expression is variable making clinical diagnosis difficult, while diagnosis by Southern blotting is relatively expensive and labour intensive. The prevalence in Singapore has not been studied. MATERIALS AND METHODS: We developed a rapid screening test using a PCR analysis. We studied 255 males with unexplained cause for learning difficulties from 8 special schools. A clinical scoring system based on characteristic features described was devised. RESULTS: PCR analysis showed absence of the band for the normal allele in 11 samples, 6 of which were confirmed by Southern blotting to be positive for FMR1 expansion, giving a 2% false-positive rate with PCR. Sensitivity of the PCR test was evaluated by performing Southern blotting in all PCR-normal samples; all of which were confirmed to be normal. This PCR test was shown to be highly reproducible. Clinical criteria were not predictive. CONCLUSIONS: Six (2.4%) new cases of fragile X syndrome were detected. There is a need to incorporate fragile X testing in routine screening of patients with developmental delay and learning difficulties. The use of PCR could eliminate the need for Southern blotting in up to 95% of cases. PCR analysis provides a simple, reliable and rapid tool for screening.

Adolescent↗
PubMed1999

Partial nephrectomy for renal tumours: the Singapore General Hospital experience.

From January 1991 to August 1998, 220 radical nephrectomies were performed for renal cell carcinoma (RCC). During the same period, 27 patients underwent partial nephrectomy for their renal tumours. These included 19 male and 8 female (mean age, 54; range, 35-75). Their clinical presentation, diagnostic modalities and surgical outcome were evaluated. The lesions included 18 RCCs, 7 angiomyolipomas (AMLs), 1 oncocytoma and 1 dysoncogenetic renal tumour. Only 8 patients had specific urological symptoms. Computerised tomography (CT) scan was diagnostic in 78% of cases. Tumour size ranged from 15-50 mm for RCC and 30-190 mm for AML, respectively. Operative time averaged 92 minutes (range: 35-145). The hospital stay ranged from 3 to 25 days (mean 11). Complications occurred in four cases (14.8%); there was one death (3.7%). No tumour recurrence was detected during a mean follow up of 20 months. None of the patients developed significant renal impairment. Partial nephrectomy is feasible in small RCC and some large AML, and can be offered in selected patients.

Adult↗