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Biomedical subjects

B K Ng

Publications and source records attributed to B K Ng.

At least 19 recordsLinked to original sources
PubMed2006

Subnanosecond-resolution phase-resolved fluorescence imaging technique for biomedical applications.

Characterization of fluorescence emissions from cells often leads to conclusive results in the early detection of cellular abnormalities. Cellular abnormalities can be characterized by their difference in the fluorescence lifetime, which may be less than nanoseconds. A sensitive frequency domain technique, also called a phase-resolved fluorescence imaging technique, is proposed in which fluorescence emissions at the same wavelengths can more effectively be separated with subnanosecond resolution in their lifetime difference. The system configuration is optimized by incorporating even-step phase shifting in the homodyne-assisted signal-processing concept along with the phase-resolved fluorescence technique to eliminate the dc offsets of emission. Experiments are carried out with simulated samples composed of two fluorescence emissions of the same wavelength but with different lifetime values. Suppression of either of the fluorescence emissions by selective imaging of the other validates the superiority of the proposed technique. Hence, this technique can potentially be applied in the early detection of cellular abnormalities.

Biomedical Engineering↗
PubMed2003

Clinics in diagnostic imaging (90). Childhood nasopharyngeal carcinoma.

An 11-year-old boy presented with a nasopharyngeal mass that was thought to represent a juvenile angiofibroma based on the initial clinical and radiological evaluation. Partial tumour resection was performed. Resected specimen revealed histological diagnosis of undifferentiated carcinoma. Further evaluation of the tumour including MR imaging, radioisotope bone scan, CT thorax and abdomen were performed. Differential diagnoses of childhood nasopharyngeal masses were discussed. The differences between childhood NPC and adult NPC, rhabdomyosarcoma, malignant lymphoma and juvenile nasopharyngeal angiofibroma were also discussed.

Carcinoma↗
PubMed2001

Continuous cardiac output monitoring system.

A continuous cardiac output monitoring system has been developed in the laboratory to allow the real-time measurement of the cardiac output. This form of continuous cardiac output measurement allows the doctor to view the beat-to-beat cardiac output and can be employed to measure artery constrictions as well. The sensor comprises a laser Doppler velocimeter and an impedance measurement unit. The laser Doppler velocimeter is capable of measuring bi-directional blood flow within the vessel while the impedance measurement unit determines the cross-sectional area of the vessel. In laboratory tests, it was demonstrated on a heart-lung machine that the product of the two parameters measured is proportional to the actual flow volume of up to 6 lmin(-1) with a mean percentage error of 12.4% and a mean square error of 0.09 (using the lmin(-1) scale) were obtained. This is significantly more accurate than the measurement made using the thermodilution cathether.

Cardiac Output↗
PubMed2001

Adjuvant postoperative 5-fluorouracil chemotherapy combined with pelvic radiation for rectal cancer: results from an Asian population.

Prospective randomized clinical trials have shown the effectiveness of combined adjuvant 5-fluorouracil-based chemotherapy and radiotherapy after surgical resection of rectal cancer. To assess toxicity of this therapy, prospective data were collected from 236 Asian rectal cancer patients treated with combined 5-fluorouracil-based chemotherapy and radiotherapy after surgery. Almost 82% of patients completed planned therapy. Grade 3 and 4 diarrhea, stomatitis, and granulocytopenia occurred in approximately 18-21% of patients. There were two treatment-related deaths from granulocytopenia and sepsis. With median follow-up of 3.5 years, median disease-free and overall survival was 75 and 88 months, respectively. In conclusion, combined adjuvant 5-fluorouracil-based chemotherapy and radiotherapy after surgical resection of rectal cancer is tolerable in Asian patients with moderate toxicity.

Adenocarcinoma↗
PubMed2001

Acute elbow trauma in children: spectrum of injury revealed by MR imaging not apparent on radiographs.

OBJECTIVE: The objective of this study is to evaluate the frequency and significance of unrecognized bone or soft-tissue injury in pediatric patients with elbow trauma assessed with radiographs alone. SUBJECTS AND METHODS: Fifty children (32 boys and 18 girls; mean age, 7.3 years; age range, 2-12 years) with acute elbow trauma were examined with radiography and MR imaging. Radiographs were categorized into those showing normal findings, an effusion, an equivocal fracture, or an unequivocal fracture. MR examinations were assessed for an effusion, fracture, transphyseal fracture extension, physeal injury, bone bruising, and ligament or muscle injury. Average clinical follow-up was 1.6 years (range, 6-28 months) after injury. RESULTS: Radiographs showed normal findings in seven children (14%), an effusion only in 17 children (34%), and an unequivocal or equivocal fracture in 26 children (52%). MR imaging showed an effusion in 48 children (96%); unequivocal fracture in 37 children (74%), including transphyseal fracture in seven children (14%) and other physeal injury in three children (6%); bone bruising in 45 children (90%); ligament injury in six children (14%); and muscle injury in 19 children (38%). A less severe spectrum of injury occurred in children with normal findings on radiographs than in those with an effusion or fracture seen on radiography. Follow-up radiographs did not help in the detection of radiographically occult fractures. MR findings had no appreciable effect on patient treatment and no value in predicting duration of convalescence or clinical outcome at an average of 1.6 years after injury. CONCLUSION: In children with elbow trauma, MR imaging reveals a broad spectrum of bone and soft-tissue injury beyond that recognizable radiographically. However, the additional information afforded by MR imaging has little bearing on treatment or clinical outcome.

Acute Disease↗
PubMed2001

Gallstone granuloma: a rare complication of laparoscopic cholecystectomy.

Gallstone spillage during laparoscopic cholecystectomy is a relatively common occurrence. These intraperitoneal stones rarely give rise to complications. We present the case of a 68 female who presented with a 5 cm diameter epigastric mass two years after a laparoscopic cholecystectomy for acute-on-chronic cholecystitis with gallbladder stones. CT abdomen demonstrated an inflammatory mass with central calcification. Laparotomy and excision of the mass revealed the diagnosis as a gallstone granuloma.

Abdominal Muscles↗
PubMed2001

Fibula pseudarthrosis revisited treatment with Ilizarov apparatus: case report and review of the literature.

A case of isolated congenital fibula pseudarthrosis with progressive valgus ankle deformity is reported. Valgus deformity can be corrected early by Ilizarov apparatus. Bone grafting is an essential part of treatment for union of the pseudarthrosis site. Internal splinting may be helpful in preventing further valgus deformity by maintaining continuity of fibula. Age of presentation has an important bearing on the choice of treatment.

Ankle Joint↗
PubMed2000

Progesterone synthesized by Schwann cells during myelin formation regulates neuronal gene expression.

Previously, progesterone was found to regulate the initiation and biosynthetic rate of myelin synthesis in Schwann cell/neuronal cocultures. The mRNA for cytochrome P450scc (converts cholesterol to pregnenolone), 3beta-hydroxysteroid dehydrogenase (3beta-HSD, converts pregnenolone to progesterone), and the progesterone receptor were found to be markedly induced during active myelin synthesis. However, the cells in the cocultures responsible for these changes were not identified. In this study, in situ hybridization was used to determine the localization of the enzymes responsible for steroid biosynthesis. The mRNA for cytochrome P450scc and 3beta-HSD were detected only in actively myelinating cocultures and were localized exclusively in the Schwann cells. Using immunocytochemistry, with minimal staining of the Schwann cells, we found the progesterone receptor in the dorsal root ganglia (DRG) neurons. The progesterone receptor in the neurons translocated into the nuclei of these cells when progesterone was added to neuronal cultures or during myelin synthesis in the cocultures. Additionally, a marked induction of the progesterone receptor was found in neuronal cultures after the addition of progesterone. The induction of various genes in the neurons was also investigated using mRNA differential display PCR in an attempt to elucidate the mechanism of steroid action on myelin synthesis. Two novel genes were induced in neuronal cultures by progesterone. These genes, along with the progesterone receptor, were also induced in cocultures during myelin synthesis, and their induction was blocked by RU-486 (a progesterone receptor antagonist). These genes were not induced in Schwann cells cultured alone after the addition of progesterone. These results suggest that progesterone is synthesized in Schwann cells and that it can indirectly regulate myelin formation by activating transcription via the classical steroid receptor in the DRG neurons.

3-Hydroxysteroid Dehydrogenases↗
PubMed2000

A case report of the use of magnesium sulphate during anaesthesia in a patient who had adrenalectomy for phaeochromocytoma.

INTRODUCTION: Patients with phaeochromocytoma have haemodynamic instability during adrenalectomy. CLINICAL PICTURE: A case showing major swings of blood pressure during tumour handling. TREATMENT: Magnesium sulphate infusion alone failed to prevent severe hypertension. OUTCOME: The patient had to be given phentolamine and sodium nitroprusside to control the severe hypertension. CONCLUSION: The greatest value of magnesium sulphate is in controlling catecholamine release at induction and intubation, and in association with other agents in controlling arrhythmias and hypertension during tumour handling.

Adrenal Gland Neoplasms↗
PubMed1999

Bone mineralization at the callotasis site after completion of lengthening.

We studied the course of bone mineralization of regenerate bone after callotasis lengthening. Twenty-three patients (eight boys) (mean age at operation 11.5 years, range 4-17 years; leg length discrepancy [LLD] at surgery ranging from 4 to 13 cm) underwent dual-energy X-ray absorptiometry (DEXA) scanning weekly during the distraction phase, at 2 week intervals until removal of the fixator, and at the time of their out-patient visits thereafter, for a mean of 794 +/- 420 days after removal of the apparatus. At removal of the fixator, the bone mineral content (BMC) of the regenerate was nearly 70% of the normal contralateral limb. With time, this value gradually increased, and tended to reach normal values, with no significant difference between femur and tibia. With time, the BMC of the regenerate tends to return to the value of the normal contralateral limb. Probably, once the limb length discrepancy has been equalized, the mechanical stimuli imparted through weight-bearing to the lengthened limb are of the same magnitude bilaterally. In this instance, then, the newly formed bone, responding to these physical stimuli, would normalize its mineral content, confirming that bone remodeling continues well after lengthening is terminated. Mineralization of the regenerate after completion of the lengthening process reaches values significantly greater than at removal of the fixator, with an increase of >50% of the prelengthening values, regardless of the underlying pathology. The final value of this increased BMC is not significantly different than in the normal contralateral unoperated limb. At least part of the increase in bone mineralization following callotasis lengthening is due to the normal process of growth and development.

Absorptiometry, Photon↗
PubMed1999

Splenic actinomycosis.

We report a rare case of abdominal actinomycosis occurring in the spleen and review the literature on abdominal actinomycosis.

Actinomycosis↗
PubMed1998

Severe progressive deformities after limb lengthening in type-II fibular hemimelia.

Until recently the accepted treatment of choice for severe type-II fibular hemimelia has been Syme's or Boyd's amputation. The alternative of distraction lengthening using the Ilizarov technique is now available. We report three patients (four limbs) with type-II fibular hemimelia who were treated by the Ilizarov technique and followed up for two to six years. Severe progressive procurvatum and valgus deformity of the tibia and valgus deformity and lateral subluxation of the ankle were found in all four limbs. Multiple additional soft-tissue and bony surgery was necessary. In view of these problems we feel that reappraisal of the indications for lengthening in type-II fibular hemimelia is necessary.

Child↗
PubMed1998

Ambulatory anorectal surgery--is it feasible locally?

Currently, anorectal procedures are done in an inpatient setting in most local hospitals. This study examines the feasibility of performing these procedures in an outpatient setting. Patients (age range 16 to 65 years) with anorectal complaints requiring surgery were randomized into 2 groups of 40 patients each. Procedures performed included haemorrhoidectomy, fistulotomy, lateral sphincterectomy, excision of rectal polyps and examination under anaesthesia. The first group was managed in the conventional inpatient setting with regional anaesthesia. The second group was done on an ambulatory basis with local anal block. Intravenous and oral ketorolac was used for postoperative pain control and patients were discharged about 4 hours postoperatively. No complications were noted in the second group while the first group had 2 cases of acute urine retention requiring temporary catheterisation and 2 cases of significant bleeding requiring hospitalisation. Pain and satisfaction scores for both groups were similar. Anorectal surgery can be performed in an outpatient setting locally with safety and efficacy. The cost savings can be significant.

Adolescent↗
PubMed1998

Adjuvant chemotherapy for patients with resected Dukes' C and high-risk B2 colon cancer with fluorouracil and levamisole.

Carcinoma of the large bowel is the second leading cause of cancer mortality in Singapore. Although the great majority of patients are discovered at a stage where resection with curative intent is possible, almost half of the patients afflicted will die of it. The combination of 5-fluorouracil + levamisole used in patients with curatively resected high risk Dukes B2 and all Dukes' C colon cancers has been shown to reduce cancer recurrence rate and improve overall survival. Since 1990 adjuvant chemotherapy has been recommended for this group of patients. This report describes patients treated in Singapore, their toxicities and their outcome. A total of 341 patients were treated between 1990 and 1996. Treatment compliance was 71.8%. Toxicity was moderate with mainly grade 1-2 nausea and vomiting, diarrhoea, stomatitis, alopecia, and neutropenia. There was 1 treatment-related death. Median recurrence-free interval was 81 months and median survival was not reached at 90 months. This regimen is tolerable. Until further randomised reports comparing 5-fluorouracil + levamisole to other combinations are available, this combination chemotherapy is recommended to patients after surgical resection of the high risk Dukes' B2 and Dukes' C colon cancer to reduce cancer recurrence and improve overall survival.

Adenocarcinoma↗
PubMed1997

Sclerosing lipogranuloma of the scrotum following a laparoscopic herniorraphy and varicocelectomy--a case report.

"Sclerosing lipogranuloma" was first coined to describe a lesion of adipose tissue thought to be due to trauma. Later, analysis of the fat within these lesions showed the presence of exogenous paraffin hydrocarbons and a link with paraffin injection was postulated. In Japan, lipogranulomas without a history of trauma or paraffin injection have been described more frequently. Our patient, developed such a lesion in his scrotum following a laparoscopic left herniorrhaphy and varicocelectomy (intra-abdominal approach). He had no prior history of trauma or paraffin injection. A possible relationship is postulated.

Adult↗