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B C Koo

Publications and source records attributed to B C Koo.

14 recordsLinked to original sources
PubMed2006

Evaluation of the photoneutron field produced in a medical linear accelerator.

The doses and spectra of photoneutrons produced in a medical linear accelerator with photon energies of 10 and 15 MV were evaluated. The Monte Carlo code, MCNPX, was used to simulate the transport of these photoneutrons around the head for 10 and 15 MV photons. The fully-described geometry of the accelerator head was used in this calculation. The photoneutron energy spectra and doses for various photon field sizes were calculated at each of 20 positions. The results indicate that the maximum dose equivalents are observed in 20 x 20 cm(2) case among photon fields. It was found the neutron average energy at isocenter for a 0 x 0 cm(2) field is 0.38 MeV for 10 MV and is 0.45 MeV for 15 MV. The neutron doses at 10 positions around the head in the treatment room of the operation facility at 10 and 15 MV were measured using the bubble detectors. Measurements were compared with the calculations under the same geometry in the experiment. It was found that the majority of the calculated results agreed to within the standard deviations of the measurements. These above results can be applied in the verification of maximum allowed neutron leakage percentage of treatment dose defined in the IEC. We have been employing them to derive the empirical formula for neutron dose equivalent level at the maze entrance of medical accelerator treatment rooms in a study that is still underway.

Algorithms↗
PubMed2006

Minimal preparation CT for the diagnosis of suspected colorectal cancer in the frail and elderly patient.

Colorectal cancer is a common malignancy with an increased incidence in the elderly population. Traditional methods of evaluating this disease have included double contrast barium enema and colonoscopy. Unfortunately, in the frail and elderly patient, these investigations can be difficult to perform and are often not tolerated. Minimal preparation computed tomography (MPCT) of the colon has been suggested as an alternative in this patient population. In this technique, no bowel preparation is used apart from the administration of oral contrast medium. The patient is imaged only in the supine position, without per rectal insufflation of gas or barium. This article reviews the experience to date of MPCT in detecting colonic tumours, and compares its efficacy to the traditional methods. A meta-analysis of the studies allowed estimation of the pooled sensitivity of MPCT to be 83% (95% confidence interval: 76-89%), and pooled specificity to be 90% (95% CI: 85-94%). An added advantage of MPCT is the ability to identify extra-colonic pathology, and this aspect is also reviewed. In addition, the common radiological features and pitfalls in identifying colonic tumours by MPCT are discussed.

Aged↗
PubMed2004

Percutaneous stone surgery in the obese: outcome stratified according to body mass index.

OBJECTIVE: To report our experience of percutaneous surgery for treating renal pelvicalyceal stones over 6 years, to show that this approach is feasible and safe in obese and morbidly obese patients, as the prevalence of obesity and stone disease has risen in the last 20 years. PATIENTS AND METHODS: We retrospectively reviewed the results of 223 percutaneous nephrolithotomies (PCNLs) by one urologist between 1995 and 2001. Patients were stratified into four groups according to the World Health Organization classification of body mass index (BMI), i.e. <25, 25-29.9 (overweight), 30-39.9 (obese) and > 40 kg/m(2) (morbidly obese). The outcomes of surgery in these four groups were compared. RESULTS: There were no statistically significant differences in operative duration, decrease in haemoglobin concentration, postoperative analgesic use, hospital stay and stone-free rates; nor was there a higher complication rate in patients who were obese. CONCLUSION: The outcome of PCNL is independent of the patients' BMI and results can be favourable in most patients. We therefore advocate treating obese patients with symptomatic stone disease based on individual status, using percutaneous surgery where appropriate.

Body Mass Index↗
PubMed2002

Review of laparoscopic urology.

Laparoscopy in urology has been slow to develop in the United Kingdom. Much of the pioneering work has been done in America and continental Europe. It is gradually gaining in popularity as urologists and the general public become more aware of the advantages it offers in terms of patient morbidity and surgical results. The aim of this review is to summarize the development of laparoscopic urology to date and to examine the various indications and the benefits of its application.

Adrenal Glands↗
PubMed1999

Comparison of the accuracy of bracket placement between direct and indirect bonding techniques.

An in vitro study was conducted to evaluate the accuracy of bracket placement for direct and indirect bonding techniques. Nineteen sets of duplicated Class II malocclusion models were divided into three groups: (1) one set for ideal bracket placement, (2) nine sets for direct bonding on mannequins, and (3) nine sets for indirect bonding. Both direct and indirect bonding were performed on all teeth except molars by nine faculty members from the Department of Orthodontics, University of Pennsylvania. The position of each bonded bracket from these two bonding groups was compared with that of the same tooth from the ideal group and to each other in terms of bracket height, mesiodistal position, and angulation. Our results indicated that both direct and indirect bonding techniques failed to execute ideal bracket placement. On individual teeth, there was no statistically significant difference in the accuracy of bracket placement between these two bonding techniques except for upper right second premolar and lower left central incisor, where indirect bonding yielded better results in bracket height (P < .05), and for lower left central incisor where indirect bonding was better in mesiodistal position (P < .05), and for upper right lateral incisor where direct bonding was closer to the ideal in angulation (P < .05). Overall, indirect bonding showed better bracket placement in bracket height (P < .05), whereas, no statistically significant difference was found between them regarding the angulation and mesiodistal position.

Dental Bonding↗
PubMed1986

Mediastinal teratoma associated with Klinefelter's syndrome.

The clinical and autopsy findings in a case of histologically benign teratoma of the mediastinum in a 19-year-old man with Klinefelter's syndrome are presented. A rough statistical analysis based on a review of the literature revealed that the incidence rate of Klinefelter's syndrome among the patients with mediastinal germ cell tumor is 30 to 40 times that of Klinefelter's syndrome among the general control population. The pathogenesis of this neoplasm appears to be related to the genetic abnormality in Klinefelter's syndrome, and this seems to predispose to the development of extragonadal mediastinal germ cell neoplasms.

Adult↗
PubMed1985

Primary mediastinal hemangiopericytoma: computed tomography correlation.

A case of primary mediastinal hemangiopericytoma with computed tomography correlation is presented. Although this is rare cause of mediastinal mass, the diagnosis should be considered when computed tomography of the mass shows contrast medium enhancement, particularly if there is a curvilinear encircling structure suggesting a large feeder vessel.

Aged↗
PubMed1984

Pulmonary vein tumor thrombosis and left atrial extension in lung carcinoma.

A case of lung carcinoma extending into left atrium through a pulmonary vein and mimicking left atrial myxoma is presented. The localized enlargement of a pulmonary vein is seen as a possible CT sign of pulmonary vein tumor thrombosis. Computed tomography (CT) and echocardiography are complementary in the correct diagnosis of this condition.

Carcinoma↗
PubMed1984

Primary myelolipoma of mediastinum.

Myelolipoma is a benign nonepithelial neoplasm composed of mature marrow elements and fat cells. This rare neoplasm is usually discovered by pathologists incidentally at autopsy, and, with rare exceptions, usually occurs in the adrenal glands. One of these exceptional anatomic sites is the mediastinum, and only three cases of primary mediastinal myelolipomas have been documented in the English-language literature (1-3). We are presenting a primary myelolipoma involving the posterior mediastinum that was discovered on routine chest radiographs and successfully resected. Computed tomography (CT) scan findings of this rare mediastinal tumor are also presented. This is the first case report in the English language of primary myelolipoma in the mediastinum that was detected clinically and resected successfully.

Humans↗
PubMed1984

Percutaneous catheter drainage in treatment of urinary extravasation.

In the last two decades there has been a rapid growth in the percutaneous manipulation of the genitourinary tract. We would like to present 2 patients in whom CT-guided percutaneous drainage of urinary extravasation was employed successfully and review the pertinent literature.

Adult↗
PubMedDate not supplied

Pineal germinoma with widespread extracranial metastases.

A case of primary pineal germinoma with widespread extracranial metastasis in a 36-year-old man is presented. A clinical work-up revealed bilateral pleural effusions, ascites, and metastatic lesions involving the lung. Cytology and electron microscopic study of the pleural and ascitic fluid and of the fine needle aspiration material revealed metastatic germinoma. Although the cytologic features were not distinct from those of anaplastic carcinoma, they were distinguishable from those of glial neoplasms, lymphoma, and sarcoma. The computed tomography findings, elevated human chorionic gonadotropin level, and electron microscopic features contributed significantly to the diagnosis of extracranial metastasis of the pineal germinoma. Metastatic spread most likely occurred via the ventriculoperitoneal shunt.

Adult↗