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Biomedical subjects

S Y Ng

Publications and source records attributed to S Y Ng.

At least 19 recordsLinked to original sources
PubMed2006

Comparison of ultrasound, digital and conventional radiography in differentiating periapical lesions.

OBJECTIVES: To carry out an in vivo comparative pilot study to evaluate the efficacy of ultrasound, digital (DR) and conventional plain film-based imaging (PF) in the differential diagnosis of periapical lesions. METHODS: Fifteen patients aged between 13 years and 40 years with periapical lesions associated with anterior maxillary or mandibular teeth requiring endodontic surgery were selected and consented for the study. Pre-operative periapical radiographs (PF) and charge coupled device (CCD) DR were obtained. Measurements and provisional diagnoses of the apical areas were made by three specialist observers (two dental radiologists and one endodontist) on three separate occasions. Pre-operative ultrasound examinations were then performed and the images assessed by two specialist observers (ultrasonographer and endodontist) for the size, contents, vascular supply and a provisional diagnosis made as to whether the lesion was a cyst or granuloma. Endodontic surgery was performed including curettage of the apical tissues to enable histopathological investigation, which provided the gold standard diagnosis. All measurements and findings were compared and statistically analysed. RESULTS: On PF and DR the periapical lesions were readily identified but observers were unable to differentiate granuloma from cyst using either modality. Dimensional measurements were subject to greater interobserver variation on DR than on PF. Where sufficient buccal cortical bone had been resorbed, ultrasound imaging was straightforward but underestimated the size of the lesions compared with PF and DR. In all 15 cases, the ultrasound diagnosis agreed with the histopathological gold standard. CONCLUSIONS: PF and DR enable diagnosis of periapical disease existence, but not of its nature; while ultrasound underestimates the extent of disease, but can provide accurate information on the pathological nature of the lesion.

Adolescent↗
PubMed2006

The in-vitro activity of colistin in gram-negative bacteria.

INTRODUCTION: Colistin is a polypeptide antibiotic belonging to the polymyxins, and has been increasingly used for the treatment of multiresistant gram-negative infections. There is little current available data on the susceptibility of gram-negative bacilli to colistin, in part because susceptibility testing for colistin remains problematic, and also because the use of colistin is not widespread. This study tested clinical isolates of gram-negative bacilli for susceptibility to colistin using the reference susceptibility testing method of agar dilution. METHODS: 102 strains of gram-negative bacilli were collected over a one-year period. Antibiotic susceptibility profiles were derived from disc susceptibility testing, and organisms were identified by standard microbiological methods. Isolates were selected for inclusion in the study using susceptibility profiles and epidemiological data. Minimum inhibitory concentrations to colistin were obtained by performing agar dilution according to a standardised method. RESULTS: 30 percent of tested isolates were resistant to colistin. All Acinetobacter spp. and Escherichia coli were susceptible to colistin. Colistin resistance was detected predominantly in Stenotrophomonas maltophilia and Pseudomonas aeruginosa, but was also present in Enterobacter spp. and Klebsiella spp. CONCLUSION: Colistin resistance is uncommon in the Enterobacteriaceae, but present in a significant proportion of S. maltophilia and P. aeruginosa isolates. From the results of this study, we recommend that susceptibility testing be performed whenever the clinical use of the polymyxins is considered.

Anti-Bacterial Agents↗
PubMed2005

Observation of tumour thickness and resection margin at surgical excision of primary oral squamous cell carcinoma--assessment by ultrasound.

Tumour thickness and the status of resection margins are of prognostic significance in the treatment of oral cancer. In a single blind prospective study, 14 patients with biopsy proven oral squamous cell carcinoma had intraoral ultrasound imaging done preoperatively to measure tumour thickness, and intraoperatively to measure the deep surgical margin half way during resection. The cut surface was demonstrated on ultrasound by placing a metal, ultrasound-reflective, retractor into the surgical cut. The ultrasound measurements were compared to the subsequent histological measurements. Using the threshold of 5mm as indicator of margin clearance, there was agreement in 10 out of 14 cases between ultrasound and histology. Ultrasound detection of close surgical margins had a sensitivity of 83% and a specificity of 63%. For preoperative tumour thickness measurement, ultrasound imaging showed a high degree of correlation with histology (Pearson correlation coefficient=0.95, P<0.01). This original paper demonstrates that high resolution ultrasound imaging applied intraorally is a reliable tool in objectively assessing both the tumour thickness and the surgical margin clearance at the time of surgery.

Carcinoma, Squamous Cell↗
PubMed2005

Tensile testing of a single ultrafine polymeric fiber.

Due to the difficulty in handling micro and nanoscale fibers and measuring the small load required for deformation, mechanical properties of these fibers have not been widely characterized. In this study, tensile test of a single-strand polycaprolactone electrospun ultrafine fiber was performed using a nano tensile tester. The tested fiber exhibited the characteristic low strength and low modulus but high extensibility at room temperature. The mechanical properties were also found to be dependent on fiber diameter. Fibers with smaller diameter had higher strength but lower ductility due to the higher 'draw ratio' that was applied during the electrospinning process.

Biocompatible Materials↗
PubMed2005

Diagnostic difficulties of complex root morphology: case study of a lower wisdom tooth.

We did a panoramic radiographic examination of a symptomatic lower third molar for surgical planning and risk assessment. This showed a close association with the inferior dental canal, in addition to uncertain root morphology. A periapical radiograph showed evidence of additional smaller curved roots. Axial computed tomography (CT) with coronal reformats did not provide further information about the morphology of the root. After removal of the tooth, its root form was compared with the diagnostic images. The periapical radiograph provided the most information about the morphology of the additional roots. The axial and reformatted coronal CT showed accurately the position and tortuous course of the inferior dental canal.

Adult↗
PubMed2003

Ultrasound imaging in the preoperative estimation of the size of tracheostomy tube required in specialised operations in children.

BACKGROUND: Some children are dependent on a tracheostomy for many years. As they grow, larger tracheostomy tubes may be required. Although tables of sizes of tracheas exist for different age groups, they are estimations of normal and may not be accurate for atypical cases. Chest radiographs and computed tomograms (CT) have been used experimentally to estimate tracheal sizes, but are not in regular use. METHOD: High-resolution diagnostic ultrasound imaging was used to estimate the internal and external transverse tracheal diameter, and the depth of the trachea from the skin surface. This allowed selection of the correct standard pattern tracheostomy tube, or the construction of a custom-made tube preoperatively. RESULTS: Four children with various abnormalities who were being considered for replacement tracheostomies were scanned. In one, diagnostic ultrasound confirmed that a new larger fenestrated tube could be placed, which subsequently improved vocalisation and respiration. In the other three, the scan showed there was no space to allow a larger tube to be placed. The standard tables were not suitable for any of these patients. CONCLUSION: High-resolution ultrasound has a role in the non-invasive measurement of the size of the tube needed for specialised operations in children.

Abnormalities, Multiple↗
PubMed2003

A new approach using intraoperative ultrasound imaging for the localization and removal of multiple foreign bodies in the neck.

An innovative method of using ultrasound imaging intraoperatively is reported. Multiple radiopaque and radiolucent foreign bodies within soft tissues were localized in theatre using high resolution ultrasonography. Depth of injury and vessel status were also ultrasonically assessed. Surgical removal of all foreign bodies was aided by intraoperative ultrasound guidance. In addition, this new approach of using intraoperative ultrasonography was pivotal in confirming the removal of all foreign bodies from the wound at the time of the operation.

Accidents, Occupational↗
PubMed2003

Use of block copolymers of poly(ortho esters) and poly (ethylene glycol) micellar carriers as potential tumour targeting systems.

Amphiphilic AB and ABA block copolymers have been prepared from poly (ortho esters) and poly (ethylene glycol). Such block copolymers readily form micellar dispersions in water, or buffers. The CMC is in the range of 3 x 10(-4)-5 x 10(-4) g/l which is a value low enough to assure retention of micelle integrity upon intravenous injection. The size, as determined by dynamic light scattering was in the 40-70 nm range. The micelles can be stored in lyophilized form for at lest 8 months and easily reconstituted to the original properties. The micelles are stable in PBS at pH 7.4 and 37 degrees C for 3 days and in a citrate buffer at pH 5.5 and 37 degrees C for 2 h. Stability in the presence of bovine serum albumin depends on the structure of the block copolymer and especially the length of the POE block.

Drug Carriers↗
PubMed2003

Decreased access to health care and social isolation among young adults with cerebral palsy after leaving school.

OBJECTIVE: To examine if leaving special schools has a negative impact on the health care and social isolation of young adults with cerebral palsy. METHODS: Young adults with cerebral palsy, aged between 15 and 22 years, were divided into 2 cohorts: current students, who were still receiving services from special schools, and school-leavers, who had since been discharged from care. A questionnaire and physical examination were administered to assess the extent of disability, health care received by, and social isolation of these young adults. RESULTS: School-leavers had a greater degree of dissability than did students, although the results were not statistically significant. Health care exposure to specialists, general practitioners, therapists physiotherapists, occupational therapists, and/or speech therapists), and medical social workers decreased after leaving school; with the exception of contact with general practitioners, these results were significant (p<0.05). The entire cohort was more socially isolated than a control cohort. School-leavers participated in fewer activities outside their homes, but showed less concern about their disability than did current students. CONCLUSIONS: Young adults with cerebral palsy continue to have health care and lifestyle needs after leaving school, which are currently not being adequately met.

Adolescent↗
PubMed2003

Interpretation of skull radiographs for facial fractures by medical staff working in UK emergency departments: a pilot study.

OBJECTIVES: This was a pilot study to determine the ability of hospital doctors (1) to assess the technical quality of occipitomental (OM) radiographs and (2) to identify facial fractures. METHOD: Twenty-two doctors from four UK Accident and Emergency (A&E) departments participated in a two part study: Part A was a postal questionnaire containing questions on demographic data, educational background, selection criteria, assessing radiographs and radiation protection; and Part B was a clinical viewing session to interpret 20 randomized OM radiographs divided into four groups; technically good and poor without fractures, and technically good and poor with fractures. RESULTS: Study participants ranged from junior house officers to senior consultants. There was considerable variation in educational background and radiographic interpretation instruction at undergraduate and postgraduate level. OM radiographs constituted 10% of all skull radiographs examined per week, yet only 40% of the doctors felt confident when assessing technical quality. The majority of participants had only a limited knowledge of radiation protection legislation. During the viewing session, only 50% of the participants correctly identified those radiographs with fractures and those with technique errors. There was no significant difference between house officers and other grades of staff. A higher level of seniority did not equate with greater interpretative ability. Subjective confidence in assessing film quality did not correlate with the actual film viewing. CONCLUSION: Only half of the A&E doctors taking part in the study were able to correctly assess film quality and identify facial fractures on OM radiographs. If the pilot sample is representative, then the findings are of considerable concern.

Clinical Competence↗
PubMed2002

Development and applications of injectable poly(ortho esters) for pain control and periodontal treatment.

Poly(ortho esters) with a low glass transition temperature are semi-solid materials so that therapeutic agents can be incorporated at room temperature, without the use of solvents, by a simple mixing procedure. When molecular weights are limited to < 5 kDa, such materials are directly injectable using a needle size no larger than 22 gauge. Somewhat hydrophilic polymers can be produced by using the diketene acetal 3,9-diethylidene-2,4,8,10-tetraoxaspiro[5.5]undecane and triethylene glycol (TEG), while hydrophobic materials can be produced by using the diketene acetal and 1,10-decanediol. Molecular weight can be reproducibly controlled by using an excess of the diol, or by use of an alcohol that acts as a chain-stopper. Erosion rates can be controlled by varying the amount of latent acid incorporated into the polymer backbone. Toxicology studies using the TEG polymer have been completed and have shown that the polymer is non-toxic. Toxicology studies using the decanediol polymer are underway. Development studies using the TEG polymer aimed at providing a sustained delivery of an analgesic agent to control post-surgical pain are under development and human clinical trials using the decanediol polymer for the treatment of periodontitis are also underway.

Anesthetics, Local↗
PubMed2002

Immune mediated chorea encephalopathy syndrome in childhood.

We report four previously healthy female children, aged between 3 and 8 years, who presented with encephalopathy and an extrapyramidal movement disorder (chorea n=4, rigidity n=2, oculogyric crisis n=2). In addition, an acute behavioural disturbance occurred in two patients and mutism in two others. Seizures heralded the onset of the illness in three patients. Acute MRI was either normal or initially normal with later generalized cerebral atrophy. All infective (including streptococcus), biochemical, and metabolic investigations were normal, although all four patients had oligoclonal bands in the (CSF) but not the serum, indicating intrathecal immunoglobulin synthesis. All four children made an apparently full recovery within four months of the onset. We suggest that these patients represent an immune-mediated movement disorder and encephalopathy syndrome.

Atrophy↗
PubMed2002

Intraoperative ultrasound imaging to aid abscess drainage--a technical note.

Diagnostic ultrasound is used widely to identify the presence of fluid collections preoperatively. Although its role in other parts of the body is well established, this report describes the technique of using diagnostic ultrasound intraoperatively to aid drainage of a large fascial space abscess in the head and neck. Following previously inadequate drainage of a large superficial abscess from a blindly placed drain, a second procedure was carried out, using ultrasound imaging to locate the persisting abscess. Furthermore, ultrasound demonstrated the adequacy of drainage and helped the surgeon to position the drain in the correct tissue space. We consider that intraoperative use of ultrasound has a role as a guidance tool to drain superficial fascial space abscesses in the head and neck region.

Abscess↗
PubMed2001

Release of BSA from poly(ortho ester) extruded thin strands.

A solventless procedure was used where powdered polymer and micronized protein were intimately mixed and then extruded into 1 mm strands that were cut to the desired length. The polymers used were poly(ortho esters) specifically designed to allow extrusion in the neighborhood of 70 degrees C. At these temperatures many proteins maintain activity in the dry state. In vitro erosion and BSA release results indicate that after a fairly long lag-time, BSA release and polymer erosion occur concomitantly indicating an erosion-controlled process. The lag-time could be eliminated by the addition to the mixture prior to extrusion between 1 and 5 wt% poly(ethylene glycol) or its methoxy derivatives. The lag-time could also be eliminated by using an AB-block copolymer where A is poly(ortho ester) and B is poly(ethylene glycol).

Crystallization↗
PubMed2001

Metachronous bilateral primary adenocarcinoma of the submandibular glands.

A young woman developed an unusual adenocarcinoma in each submandibular salivary gland at an interval of 30 months. This presentation has not been described previously. The possible etiology for this and treatment options are discussed. The choice of diagnostic imaging (ultrasound versus magnetic resonance imaging) is highlighted. As a result of regular follow-ups using diagnostic ultrasound, a second tumor was observed to reach a dimension of 8 mm in less than 6 months. This is probably the first report documenting the extent of initial growth of this rare tumor.

Adenocarcinoma↗
PubMed2001

Ultrasound features of osteosarcoma of the mandible--a first report.

Ultrasound imaging is becoming widely used in the head and neck region as a first-line investigation to assess soft tissue swellings. Clinicians should be aware of the potential of diagnostic ultrasound to identify important signs of malignant disease involving bone. Involvement of the mandible by osteosarcoma is uncommon. A young adult patient presented with facial swelling and an apparently infected lower third molar extraction socket. Subtle signs were missed on dental radiographs. Diagnostic ultrasound investigation was pivotal in identifying sinister signs: namely, soft tissue mass associated with bone thinning, erosion, expansion, and the "sunray" appearance of the buccal cortex, which were suggestive of osteosarcoma. These findings enabled priority to be given to subsequent investigations using other modalities. We present a first report of the ultrasound features of osteosarcoma of the mandible and consider this to be a useful modality in an initial investigation.

Adult↗