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Biomedical subjects

J W Wong

Publications and source records attributed to J W Wong.

9 recordsLinked to original sources
PubMed1992

Fine-needle aspiration biopsy of hepatic angiosarcoma: report of a case with immunocytochemical findings.

Hepatic angiosarcoma (Kupffer cell sarcoma) is a very rare but ominous malignancy. We report a case diagnosed by fine-needle aspiration biopsy (FNAB). The smear showed malignant spindle cells and a few rounded cells. The diagnosis was made on the cell block by the characteristic scaffolding arrangement of malignant cells along preexisting hepatocytes. This is the first report with immunocytochemical findings. The tumour cells stained positively for vimentin and negatively for keratin, factor VIII, Ulex europaeus agglutinin I (UEA-1), carcinoembryonic antigen (CEA), alpha-fetoprotein (AFP), and lysozyme. This case demonstrates the possibility of a definitive diagnosis by FNAB prior to death without inflicting serious complications.

Aged↗
PubMed1992

Rapid two-dimensional dose measurement in brachytherapy using plastic scintillator sheet: linearity, signal-to-noise ratio, and energy response characteristics.

Because of the large dose gradients encountered near brachytherapy sources, an efficient, accurate, low-atomic number areal detector, which can record dose at many points simultaneously, is highly desirable. We have developed a prototype of such a system using thin plates of plastic scintillator as detectors. A micro-channel plate (MCP) image intensifier was used to amplify the optical scintillation images produced by radioactive 125I and 137Cs sources in water placed 0.5-5.7 cm distance from the detector. A charge-coupled device (CCD) digital camera was used to acquire 2-D light-intensity distributions from the image intensifier output window. For both isotopes, a small area (2 x 3 mm2) PVT detector yields a CCD net count rate that is linear with respect to absorbed dose rate within +/- 3% out to 5.7 cm distance. Acquisition times range from 1.5-400 sec with a reproducibility of 0.5-5.5%. If a large-area (6 x 20 cm2) PVT detector is used, a four-fold increase in count rate and large deviations from linearity are observed, indicating that neighboring pixels contribute light to the signal through diffusion and scattering in PVT and water. A detailed noise analysis demonstrates that the image intensifier reduces acquisition time 10000-fold, reduces noise relative to signal 200-fold, and reduces amplifier gain noise as well.

Brachytherapy↗
PubMed1992

Surgery for cardiac arrhythmias.

From March 1989 to March 1991, 17 patients underwent curative surgical ablation of cardiac arrhythmias at the Singapore General Hospital. In the supraventricular tachycardia group, 13 patients with the Wolff-Parkinson White syndrome (WPW) underwent surgical ablation of the accessory conduction pathway by the classical endocardial approach. Two patients who had atrioventricular nodal tachycardia (AVNRT) underwent surgical dissection around the atrioventricular node to divide one of the dual conduction pathway responsible for the tachycardia. In the ventricular tachycardia group, two patients underwent surgical ablation of the arrhythmic focus. There was no operative mortality in the supraventricular tachycardia group and there were no late deaths to date. All these patients underwent electrophysiological study just before discharge and most of them had a repeat test six months later. In the Wolff-Parkinson White group, surgical ablation was completely successful in 12 patients (92%), preexcitation recurred in one patient (8%) but non had recurrence of supraventricular tachycardia. The two patients who had atrioventricular nodal tachycardia were completely cured of recurrent supraventricular tachycardia and had normal atrioventricular conduction. In the ventricular tachycardia group, one was cured with no recurrence of tachycardia, is not on medication and is in New York Heart Association Class I status. The other died postoperatively of recurrent ventricular tachycardia and low cardiac output syndrome.

Adult↗
PubMed1992

Surgical management of intrathoracic aortic aneurysm.

The pathology, clinical features, indications for surgery and the results of intrathoracic aneurysm are analysed in thirty-nine consecutive patients who underwent surgery at Singapore General Hospital from January 1986 through December 1990. There were twenty cases of non-dissecting aneurysm and nineteen cases of dissecting aneurysm or aortic dissection. The 30 day survival for the twenty patients with non-dissecting aneurysm was sixteen patients (80%). The best results were obtained in patients with aortic root aneurysms. The overall 30-day survival for the nineteen patients with aortic dissection was twelve patients (64%). The mortality was especially high in patients with acute aortic dissection (46%). Recent advances in the management of these aneurysms make early recognition and diagnosis mandatory to achieve the best results.

Adult↗
PubMed1977

Effects of gravity on tracheal mucus transport rates in normal subjects and in patients with cystic fibrosis.

A noninvasive, radionuclide imaging technique for measuring the rate of mucus clearance in the trachea (RT), was used to study gravitational effects on mucus clearance in 13 patients with cystic fibrosis (CF), average age 17 years; 7 normal, nonsmoking adults, average age 26 years; and a normal subject who was recovering from an acute upper respiratory tract infection (URTI). In the upright position, nine of the CF patients and the subject with URTI demonstrated abnormal tracheal mucus clearance which approached normal when they were placed in 25 degrees headdown position. The normal subjects and two of the CF patients showed no significant difference in the RT measured in the two positions. The results of the study indicate that the force of gravity can be a major influence on tracheal mucus clearance in CF and URTI subjects. This conclusion supports the use of postural drainage as an effective form of therapy in patients with cystic fibrosis.

Adolescent↗
PubMedDate not supplied

Verification data for electron beam dose algorithms.

The Collaborative Working Group (CWG) of the National Cancer Institute (NCI) electron beam treatment planning contract has performed a set of 14 experiments that measured dose distributions for 28 unique beam-phantom configurations that simulated various patient anatomic structures and beam geometries. Multiple dose distributions were measured with film or diode detectors for each configuration, resulting in 78, 2-D planar dose distributions and one, 1-D depth-dose distribution. Measurements were made for 9- and 20-MeV electron beams, using primarily 6 x 6- and 15 x 15-cm applicators at several SSDs. Dose distributions were measured for shaped fields, irregular surfaces, and inhomogeneities (1-D, 2-D, and 3-D), which were designed to simulate many clinical electron treatments. The data were corrected for asymmetries, and normalized in an absolute manner. This set of measured data can be used for verification of electron beam dose algorithms and is available to others for that purpose.

Algorithms↗