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Biomedical subjects

R Wong

Publications and source records attributed to R Wong.

250 records · Page 14Linked to original sources
PubMedDate not supplied

Epidemiologic health study of workers in an aluminum smelter in Kitimat, B.C. II. Effects on musculoskeletal and other systems.

A health study was carried out on 2066 workers in an aluminum smelter in Kitimat, British Columbia to study the effects of exposure to fluoride and other air contaminants encountered on the potlines on the musculoskeletal system, hemopoietic tissue, liver, and renal function. Three hundred seventy-two railway repair workers from Squamish, British Columbia served as an "external" control group. Examination of the spine and sacroiliac joints and pelvic X-ray were conducted on long-term potline workers and a number of "internal" control workers in the smelter not exposed to any air contaminants. Urinary fluoride measurements and personal sampling for airborne fluoride were also carried out. Blood samples were collected for routine blood count and liver and renal function test. Definite cases of skeletal fluorosis were not found in any potroom workers. Some of the changes of early skeletal fluorosis described on pelvic X-rays, e.g., increased density, calcification of ligaments, and periosteal changes, were found in a few workers who were employed on the potlines for more than 10 yr. There was, however, poor agreement in the findings of the two radiologists who read the films. The entity "musculoskeletal fluorosis" does not exist in this smelter where the potroom workers were exposed to total fluoride levels below the currently accepted threshold limit value of 2.5 mg/m3. No ill effects on the hematopoietic tissue or liver and renal function were found.

Air Pollutants↗
PubMedDate not supplied

Assessment of patient exposure for barium enema examinations.

Methods are described for the assessment of patient exposure during clinical fluoroscopic procedures. Values of the roentgen-area-product (RAP) and their distribution throughout the examination are presented for both single-contrast and double-contrast barium enema studies. The double-contrast procedure was measured to give 50% more radiation to the patient than the single-contrast procedure when the same size optical aperture is used between the intensifier and TV pick-up tube. However, it was possible to decrease the fluoroscopic RAP value by over a factor of two for the double-contrast procedure without an adverse clinical effect by increasing the area of the aperture diaphragm.

Barium Sulfate↗
PubMedDate not supplied

Design of rotating aperture cones for radiographic scatter reduction.

A new multiple-scanning-slit or scanning-grid scatter-reduction geometry consisting of coaxial rotating aperture (RA) cones is described and compared with other RA assemblies such as the rotating aperture wheel (RAW) device. A unique feature of the new design is that the geometric and rotational axes of the conical RA surfaces coincide and are collinear with the x-ray focal spot. This arrangement of axes should provide the potential for greatly improved mechanical rigidity, higher rotational velocities, and the capability for static slit-pattern alignment. The common rotational axis of the cone assembly is angled obliquely to the central x-ray beam such that the intersections of the irradiated portion of the RA surfaces with the plane formed by the x-ray central beam and cone axes are straight lines parallel to the film plane. This geometry is compatible with the standard source-patient-image receptor radiographic relationship and allows for variable source-to-image-receptor distance.

Radiography↗
PubMedDate not supplied

Improving fluoroscopic image quality with continuously variable zoom magnification.

Coning down is commonly used during fluoroscopy to increase image contrast by reducing scatter. However, the resulting image fills only part of a video display whose resolution is limited by line rate and bandwidth. Optical or electron-optical zooming can be used to magnify the collimated image so that it fills a larger fraction of the viewable area of the video frame to make more effective use of the available video-display capacity. Modulation-transfer functions (MTFs) were measured for various zoom factors achieved using a zoom lens and the image-intensifier (II) electronic magnification mode. Significant and continuing improvement in total system MTF was observed up to zoom magnifications of greater than 3.3. For larger zoom factors, the resolution limit becomes dominated by the intrinsic resolving power of the II and by geometric unsharpness rather than by the line rate of the video system. When the MTF at infinite zoom factor, obtained by extrapolation, was divided into the measured MTFs, the resultant MTFz's were shown to scale predictably with zoom factor. Only a slight improvement in MTF was obtained using the II's electronic magnification mode compared to the same magnification using a zoom lens. It is concluded that, if improved image quality is the motivation for the use of coning down in fluoroscopy, then zooming to use fully the available video frame is warranted.

Fluoroscopy↗
PubMedDate not supplied

Accurate characterization of image intensifier distortion.

Image intensifier distortion due to photocathode curvature and electron optics is shown to be approximated by a simple two parameter odd-power polynomial. The accuracy of this fit was found to be far better than that of two other one parameter characterizations of distortion when applied to experimental data from four different model image intensifiers ranging in diameter from 9 to 14 in. The standard errors of the two parameters fits were less than 0.1 mm or 0.03% of the field of the IIs and were within the estimated measurement error.

Technology, Radiologic↗
PubMedDate not supplied

Luminance range compression for video film digitizers.

Video cameras are used in many film digitization and teleradiology systems. However, the density range of medical radiographs often exceeds the dynamic range of the camera, and all diagnostic information in the original image may not be captured. Information in both the high and low density areas of the film can be captured in a single video frame if the transmitted luminance range of the radiograph is reduced. This can be accomplished by spatially modulating the back illumination of the film such that areas of lesser density receive less illumination while areas of greater density receive greater illumination. In this work, the use of a video monitor is shown to be an effective means to provide spatially modulated light for compressing the transmitted luminance range and thereby expanding the apparent dynamic range of the video camera. A simple computer-interfaced video feedback system that determines the appropriate compression mask and a scheme for linearization of system response are described. This system provides an interactive means for control of the degree of range compression.

Analog-Digital Conversion↗
PubMedDate not supplied

Hemangioendothelioma of the spinal cord with intramedullary extension.

OBJECTIVE: Hemangioendotheliomas (HE) are vascular neoplasms that rarely involve the neuraxis. We report a rare case in the literature of intradural HE of the spinal cord with intramedullary extension. CLINICAL PRESENTATION AND INTERVENTIONS: A 41-year-old gentleman presented with low back pain, numbness and urinary retention. Imaging revealed a spinal tumor causing complete blockage at the level of T12. The tumor was resected and postoperative radiotherapy was delivered for residual disease. No disease was seen on MRI after 48 months of clinical and radiological follow-up. CONCLUSION: Complete excision of HE is the treatment of choice. Radiotherapy may play a role in the management of this lesion.

Adult↗
PubMedDate not supplied

Role of poloxamer 188 during recovery from ischemic spinal cord injury: a preliminary study.

Paraplegia following aortic surgery is not a common event. When it does occur it significantly alters the patient's outcome. Poloxamer 188 (P188) has been shown in the experimental animal to increase regional blood flow to ischemic areas. In order to investigate its protective effect during aortic cross-clamping, 23 animals were randomized to two groups (placebo n = 11, P188n = 12) and received an intravenous injection of placebo or P188 (200 mg/kg), and underwent occlusion of the thoracic aorta and both subclavian arteries for a period of 13 minutes. They were then connected to an intravenous pump delivering either placebo or P188 (250 mg/kg/hr at a rate of 0.942 ml/hour) for 48 hours. Hindlimb function was appraised, daily for 30 days, by a lesion score (0-15). Spinal cord injury was assessed by a histologic score (0-3) based on the degree of gray and white matter gliosis, number of motor neurons, and white matter myelination. Analysis of variance for repeated measures did not reveal significant difference between P188 and placebo groups (P = 0.66). Similarly, the mean histologic scores (placebo = 1.54 +/- 0.41 SE, P188 = 1.08 +/- 0.33 SE) did not differ (Wilcoxon, P = 0.43). We conclude that intravenous administration of P188 before, during, and for 48 hours after aortic cross-clamping does not prevent paraplegia or improve the long term neurologic outcome.

Animals↗
PubMedDate not supplied

Exogenous iron overload in perinatal hemochromatosis: a case report.

We report an infant with fatal neonatal liver disease in whom efforts to correct an associated unremitting anemia resulted in massive exogenous iron overload that was expressed as perinatal hemochromatosis (PH). Levels of iron and copper were elevated in multiple tissues. Echovirus subtype 9, recovered from the urine at age 3 weeks, may have been etiologic in the liver failure. PH is best viewed as a definable phenotype with an undefined genetic and/or environmental basis that emerges only in the context of severe perinatal liver disease. The absence of hemosiderin in splenic and bone marrow reticuloendothelial (RE) cells of our patient suggests an important role for RE cell dysfunction.

Anemia↗
PubMedDate not supplied

Hyperactivity and learning deficits in transgenic mice bearing a human mutant thyroid hormone beta1 receptor gene.

Resistance to thyroid hormone (RTH) is a human syndrome mapped to the thyroid receptor beta (TRbeta) gene on chromosome 3, representing a mutation of the ligand-binding domain of the TRbeta gene. The syndrome is characterized by reduced tissue responsiveness to thyroid hormone and elevated serum levels of thyroid hormones. A common behavioral phenotype associated with RTH is attention deficit hyperactivity disorder (ADHD). To test the hypothesis that RTH produces attention deficits and/or hyperactivity, transgenic mice expressing a mutant TRbeta gene were generated. The present experiment tested RTH transgenic mice from the PV kindred on behavioral tasks relevant to the primary features of ADHD: hyperactivity, sustained attention (vigilance), learning, and impulsivity. Male transgenic mice showed elevated locomotor activity in an open field compared to male wild-type littermate controls. Both male and female transgenic mice exhibited impaired learning of an autoshaping task, compared to wild-type controls. On a vigilance task in an operant chamber, there were no differences between transgenics and controls on the proportion of hits, response latency, or duration of stimulus tolerated. On an operant go/no-go task measuring sustained attention and impulsivity, there were no differences between controls and transgenics. These results indicate that transgenic mice bearing a mutant human TRbeta gene demonstrate several behavioral characteristics of ADHD and may serve a valuable heuristic role in elucidating possible candidate genes in converging pathways for other causes of ADHD.

Animals↗
PubMedDate not supplied

[Household structure as a response to economic adjustments: evidence from urban Mexico in the 1980s].

"This paper presents the results of exploratory efforts to examine the determinants of the structure of households in urban areas of Mexico, focusing on those of women with young children.... The empirical analysis uses two cross-sectional national surveys of Mexico, the 'Encuesta Nacional Demografica' 1982 and the 'Encuesta Nacional de Fecundidad y Salud' 1987...." (SUMMARY IN ENG)

Americas↗
PubMedDate not supplied

Computer frame freezing of fluoroscopic images.

Simple but flexible frame freezing of fluoroscopic images can improve the utility of real-time x-ray imaging. A frame-freeze system based on a personal computer has been developed. The system is easily installed using standard hardware that is non-invasive of the fluoroscopic imaging chain. The frozen images can be used as a reference or for hard-copy documentation of real-time or videotaped procedures.

Fluoroscopy↗
PubMedDate not supplied

Acute myocardial infarction: contemporary risk and management in older versus younger patients.

The in-hospital management and risk of death of 101 patients 70 years of age or older with acute myocardial infarction in 1987 (group 1) were compared with management and risk for 106 temporally matched patients less than 70 years old (group 2). In group 1, 49% had histories of previous myocardial infarction, compared to 25% in group 2 (P less than 0.001), and 23% of group 1 presented without cardiac pain, versus 7% of group 2 (P less than 0.001). Among the younger patients, other conventional risk factors were, in contrast, more common (Q wave infarction 84% in group 2 versus 70% in group 1; P less than 0.05) or higher (peak creatine kinase values 2222 iu/L in group 2 versus 1366 iu/L in group 1; P less than 0.001). Prior to infarction, all cardiac drugs were used more frequently in the older group 1 patients, whereas post infarction thrombolysis, beta-blockers and acetylsalicylic acid use were all more common (P less than 0.01 to P less than 0.001) in the younger group 2 patients. Post infarction exercise testing, left ventricular ejection fraction calculations and coronary angiography were all performed less frequently in group 1 (P less than 0.001). The in-hospital mortality was 35% for group 1 versus 7% for group 2 (P less than 0.001). Among all 207 study subjects, multiple logistic regression revealed thrombolysis, absence of cardiac pain, and age 70 years or older to be associated with the greatest relative mortality risk. Increased relative risk to a lesser degree was associated with previous infarction, male sex and post infarction use of antiarrhythmic medication.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

A cost analysis of a professional practice model for nursing.

Costs of nursing care among hospital units that adopted a professional practice model (PPM) were compared with traditional nursing units. PPM inpatient units used fewer temporary personnel and nursing aides, resulting in similar RN costs but lower total nursing costs. However, PPM operating rooms were more costly, mostly because of the intense use of RNs.

Cost-Benefit Analysis↗
PubMedDate not supplied

Pharmacokinetics of mycophenolate mofetil and intravenous ganciclovir alone and in combination in renal transplant recipients.

STUDY OBJECTIVES: To evaluate the pharmacokinetics of mycophenolic acid and its glucuronide metabolite alone and in the presence of ganciclovir, and to determine the pharmacokinetics of ganciclovir alone and in combination with mycophenolate mofetil. DESIGN: Randomized, open-label, three-way crossover study. PATIENTS: Twelve kidney transplant recipients. INTERVENTIONS: Mycophenolate mofetil 1500 mg orally and ganciclovir 5 mg/kg intravenously were each given alone and in combination with at least a 1-week washout period between treatment arms. MEASUREMENTS AND MAIN RESULTS: Blood samples were obtained to measure mycophenolic acid and ganciclovir by high-performance liquid chromatography. Mean (+/-SD) oral plasma clearance for mycophenolic acid alone and with ganciclovir was 3.11 +/- 0.72 and 3.19 +/- 0.72 ml/min/kg (p = 0.64). The overall disposition of the major metabolite, MPA-glucuronide, was unchanged, with approximately 70% of the administered dose eliminated as the glucuronide conjugate for both arms of the study. Mean genciclovir serum clearance was 1.80 +/- 0.58 ml/min/kg for ganciclovir and 1.70 +/- 0.55 ml/min/kg for ganciclovir plus mycophenolate mofetil (p = 0.11; 10 patients). Renal clearance of ganciclovir was decreased when the drugs were administered in combination, 1.43 +/- 0.54 (ganciclovir) and 1.26 +/- 0.44 (both drugs) ml/min/kg (p = 0.02; 10 patients). CONCLUSION: The single-dose pharmacokinetics of mycophenolic acid and its glucuronide metabolite were unchanged by the addition of ganciclovir. Total serum clearance of ganciclovir was unchanged by the addition of mycophenolate mofetil, however, renal clearance was slightly decreased.

Adult↗