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Biomedical subjects

C R Wilson

Publications and source records attributed to C R Wilson.

At least 55 records · Page 3Linked to original sources
PubMed1993

Computed equalization radiography: preliminary clinical evaluation.

Computed Equalization Radiography (CER) was designed to increase visualization of mediastinal structures without affecting lung contrast. CER optimizes the image by obtaining two 1-second fan beam scans. The initial low-dose prescan determines the location of the lungs by means of a stationary krypton gas detector. During the equalization scan, this information is used to position 35 beam attenuators in real time so as to increase exposure of the mediastinum while maintaining ideal optical density over the lungs. Eight observers analyzed 20 pairs of posteroanterior (PA) and lateral radiographs obtained on conventional and CER units. On the PA images, three of four mediastinal areas analyzed were visualized better in CER images, while there was no difference in lung detail. There were no appreciable differences in the lateral projection between the CER and conventional images. Contrast on the PA radiograph was preferred on the CER image. CER provided modest improvement in visualization of mediastinal structures and maintained lung contrast without degrading lung detail on the PA image. CER had no major effect on visualization in the lateral images.

Diagnosis, Computer-Assisted↗
PubMed1992

Resistance to phloem transport of potato leafroll virus in potato plants.

A 'double-graft sandwich' technique in which sections of potato stem from different potato cultivars were grafted between a susceptible healthy stock plant and a potato leafroll virus (PLRV)-infected scion was used to study the rate of phloem transport of PLRV in cultivars differing in resistance to PLRV infection (IR) and accumulation (AR). Resistance to phloem transport (i.e. delayed PLRV systemic movement) was found in Bismark cultivar (IR A(S)). This was independent of IR and AR as the rate of movement in Bismark cultivar was markedly slower than that in Omega and Spunta (IR AR), Delaware (I(S) AR), and Desiree and Renova (I(S) A(S)) cultivars. It operated in Bismark cultivar stems of two different ages, but did not operate against potato virus X (PVX) and was not influenced by previous infection with this virus. Aphid vector (Myzus persicae) feeding preferences and colonization rates differed between cultivars, but the cultivar characteristics responsible were unrelated to IR, AR or resistance to phloem transport. Delayed systemic movement of PLRV out of leaves inoculated with viruliferous aphids was independent of AR and resistance to phloem transport, and remained unaffected by previous infection with PVX. It was also independent of cultivar factors causing different aphid feeding preferences and colonization rates, but may be linked to IR.

Biological Transport↗
PubMed1992

Iodine-131 contamination from thyroid cancer patients.

High-dose radioactive iodine therapy using 131I is the treatment of choice for patients with thyroid cancer following thyroidectomy. Because of the large amount of activity which is excreted during hospitalization, contamination hazard from 131I excretion via perspiration, saliva, breath and urine may arise. In eight patients treated with doses of 131I ranging from 3.7 to 14.8 GBq (100-400 mCi), activity levels were measured in room air, from room surfaces, the toilet, the patients' exhaled breath, skin, saliva and toothbrushes, and the gloves used by medical staff. Thyroid bioassays were also performed on medical staff personnel caring for these patients both before and two days after administration of the treatment dose. Removable activity from the skin was positively correlated with treatment dose and reached a maximum at 24 hr post-therapy. Removable activity from room surfaces exceeded the level of contamination which requires clean-up in a restricted area during the patient's hospitalization. Thyroid bioassays on medical staff showed no significant uptake 2 days after treatment. The relatively high activities present in the saliva, urine and on the skin of these patients emphasizes the need for all individuals coming in contact with these patients to be made aware of the contamination hazard present.

Adolescent↗
PubMed1991

The effect of positioning on dual energy X-ray bone densitometry of the proximal femur.

The influence of subject repositioning on the precision of bone mineral densitometry of the proximal femur using dual energy X-ray absorptiometry was estimated by determining the variation in the bone mineral density (BMD) of subjects scanned with their foot and leg position varying from that routinely used in clinical scanning. The mean variations in BMD of the femoral neck, Ward's triangle and trochanter were 2.7, 4.1 and 1.7%, respectively, in eight subjects scanned with the foot internally rotated by 0, 13 and 27 degrees. The mean variations in BMD in four subjects scanned with the leg in the customary position and abducted +/- 6 degrees from the conventionally used scanning position were 3.6, 2.8 and 1.6% for the same respective regions of interest. For diagnostic applications, the orientation of the leg and foot during scanning is relatively unimportant since the variations in BMD introduced by the different foot and leg orientations likely to be encountered in routine clinical scanning are small compared to the intrapopulation variation in BMD. However, for monitoring changes in BMD longitudinally, careful repositioning of the foot and leg will be necessary to achieve precision in vivo of less than 1%.

Absorptiometry, Photon↗
PubMed1991

Relationship of regional fat distribution and obesity to electrocardiographic parameters in healthy premenopausal women.

Abdominal obesity is an independent cardiovascular risk factor. The coexistence of abdominal obesity and electrocardiographic abnormalities may facilitate the development of cardiac arrhythmias and sudden death. We determined the relationship of body fat distribution and obesity to ECG indices in 27 obese premenopausal women on an isocaloric diet. Intra-abdominal fat distribution was assessed by computerized tomography, and obesity was assessed by hydrostatic weighing. The PR, QRS, and QTc intervals, the P and QRS axes, and the P-QRS angle were determined from a resting electrocardiogram. Cardiovascular risk profile was assessed by systolic and diastolic blood pressure and plasma cholesterol and triglyceride levels. Increased deposition of intra-abdominal fat was significantly associated with prolongation of the QTc interval independent of obesity and other cardiovascular risk factors. The prolongation of the QTc interval seen with increasing intra-abdominal fat distribution may enhance susceptibility to cardiac arrhythmias. These subjects should have electrocardiographic monitoring during periods of weight loss achieved by intensive regimens.

Abdomen↗
PubMed1990

In vitro biomechanical study of female geriatric cervical vertebral bodies.

Compressive strength tests were conducted on fresh human geriatric female cervical vertebral bodies. Nineteen specimens were compressed to 50% of their initial height using an electrohydraulic testing device. The mechanical force-deflection response was sigmoidal with continuously changing resistance. The mean cross-sectional area and bone mineral content (BMC) of the vertebral bodies progressively increased from C3 (area: 333.8 mm2, BMC: 1.56 g) to C6 (area: 499.7 mm2, BMC: 2.18 g). The maximum compressive force increased from 1060 N at C3 to 1787 N at C6. The stiffness and the energy absorbed at failure also increased from C3 to C6 (stiffness: 279.95 to 556.41 N mm-1, energy: 2.45 to 4.16 J). These parameters demonstrated a decreasing tendency from C6 to C7. The relatively higher biomechanical parameters at the sixth vertebral level compared with its caudad and cephalad counterparts may be due to the fact the transition of the cervical lordosis to thoracic kyphosis begins at this level. Furthermore, the change in the anatomy of the unicinate processes in the cervical column around this region may also be a contributing factor.

Aged↗
PubMed1989

Adiposity, fat distribution, and cardiovascular risk.

STUDY OBJECTIVE: To determine the relative importance of adiposity and fat distribution to cardiovascular risk profile. DESIGN: A cross-sectional study. SETTING: Clinical research center funded by the National Institutes of Health. PATIENTS: Convenience sample of 33 healthy premenopausal women with a wide range of body weight who did not have diabetes mellitus, hirsutism and virilism, gynecologic disorder, cardiac disease, or hypertension. Women participating in exercise or dietary programs or taking medication were excluded. All subjects completed the study. INTERVENTIONS: Total body fat mass was determined by hydrostatic weighting, and fat distribution was assessed by subscapular skinfold thickness, subscapular-to-triceps skinfold ratio, the waist-to-hip ratio, and computed tomography. Cardiovascular risk was assessed by the serum insulin response during oral glucose stimulation; levels of triglycerides and total cholesterol; high-density lipoprotein cholesterol to total cholesterol concentrations; and systolic and diastolic blood pressures. MEASUREMENTS AND MAIN RESULTS: The anthropometric parameters chosen were significantly associated with the cardiovascular risk profile (P less than 0.001). Visceral fat distribution assessed by computed tomography accounted for a significantly greater degree of variance in the cardiovascular risk factors than the total body fat mass (P less than 0.05). The cumulative insulin response was the primary metabolic variable relating the anthropometric indices to cardiovascular risk. CONCLUSIONS: Intra-abdominal fat deposition constitutes a greater cardiovascular risk than obesity alone. Hyperinsulinemia may constitute an important component of the increased cardiovascular risk of abdominal obesity.

Adipose Tissue↗
PubMed1989

Rehabilitation for employment. The Rehabilitation Centre of the Association for the Physically Disabled at Bridgetown, Athlone, CP.

Results of rehabilitation of physically disabled people for employment on the open labour market over the period 1975-1985 are presented. Out of 680 eligible clients, 53% were successfully placed. When corrected for uncontrollable withdrawals and uncontrollable dismissals the success rate rises to 77% (363 of 471 clients). The drop-out rate of 16% for preventable reasons and a partially preventable wastage of 31% are highlighted for potential action and improvement. The main reasons for admission were trauma (motor vehicle accidents, assaults and industrial injuries), poliomyelitis and congenital abnormalities in a ratio of 4:3:1. These groups accounted for 82% of all admissions. The problem of adequate evaluation and screening to predict outcome reliably is discussed and the use of a modified version of the International Classification of Impairments, Disabilities and Handicaps of the World Health Organisation is advocated. Of those clients who were successfully placed, 75-80% remained in employment for more than 1 year and 55-60% for more than 2 years. On the whole, the rehabilitation process appears to lead to successful re-integration into the working community for most of the physically disabled persons admitted to the Centre.

Persons with Disabilities↗
PubMed1989

Relative contribution of obesity and body fat distribution to alterations in glucose insulin homeostasis: predictive values of selected indices in premenopausal women.

Obesity and fat topography are risk factors for hyperinsulinemia, insulin resistance, and diabetes mellitus. The relative contribution of obesity and body fat distribution indices to fasting and oral glucose-stimulated C peptide, insulin, and glucose concentrations were determined in 33 healthy premenopausal women. Obesity level was assessed by hydrostatic weighing and fat topography by computerized tomography-derived intraabdominal fat area, waist to hip ratio, subscapular skinfold thickness and the ratio of subscapular to triceps skinfold thickness. Both fat mass and regional fat distribution indices were associated closely with changes in insulin secretion. Fat topography indices were more closely correlated (p less than 0.001) to insulin response than were fat mass indices (p less than 0.01). The subscapular skinfold thickness had the greatest integrity for reflecting fat mass and fat distribution as they relate to the metabolic profile. The subscapular skinfold thickness may help identify individuals at risk for noninsulin dependent diabetes mellitus.

Adipose Tissue↗
PubMed1988

Relationship of anthropometric measurements of body fat distribution to metabolic profile in premenopausal women.

Regional fat distribution has emerged as an independent predictor of metabolic aberrations including glucose intolerance, hyperinsulinemia, insulin resistance, hyperlipidemia and hypertension. We investigated the comparative efficacy of various body fat distribution indices in predicting these aberrations. The relationship of circumferential ratios, skinfold measurements, and computerized tomography (CT)-derived indices of intra- and extra-abdominal fat distribution to the metabolic variables and blood pressure was examined in a cohort of healthy premenopausal women. All indices denoting preponderance of fat in the central, upper body or abdominal region were predictive of the metabolic profile. The subscapular skinfold, subscapular-triceps ratio, waist-hip ratio (WHR), and the CT derived intra-abdominal fat area (CT-IFA) were closely related to alterations in glucose and insulin concentrations independent of age and obesity. The WHR and CT-IFA were better predictors of plasma triglyceride levels and blood pressure profile and thus the overall aberrations than skinfold measurements. Despite a high degree of intercorrelation between the anthropometric indices measured, only the relationship of WHR to CT-IFA remained significant after adjusting for the effects of age and degree of adiposity, suggesting that WHR indexes not only the relative distribution of truncal to gluteofemoral subcutaneous fat but also the abundance of intra-abdominal or visceral fat depots. The greater reproducibility of CT-IFA and WHR also suggests that these measurements are the most useful in predicting the regional obesity-associated metabolic abnormalities with their morbidity and mortality risks.

Adipose Tissue↗
PubMed1988

Pneumothorax and other lung diseases: effect of altered resolution and edge enhancement on diagnosis with digitized radiographs.

Prior studies have shown that pneumothorax is one of the more difficult entities to diagnose with digitized radiography. This study was designed to test whether increasing resolution from 1.25 to 2.5 line pairs per millimeter (lp/mm) and image processing (edge enhancement from unsharp masking) would increase accuracy and confidence in the diagnosis of pneumothorax, as well as normal cases and other forms of lung disease. Conventional radiographs were digitized with use of a laser reader and then reformatted as film hard copy. Eleven observers read 35 cases reformatted in three different ways (1.25 lp/mm, 2.5 lp/mm, 1.25 lp/mm unsharp mask). The images with finer resolution (2.5 lp/mm) and unsharp mask images were superior to those with coarser resolution (1.25 lp/mm) for the diagnosis of pneumothorax. There was no difference in diagnostic accuracy for normal patients. For abnormalities other than pneumothorax, the unsharp mask images were significantly worse. Confidence in the diagnosis of pneumothorax and other abnormalities was highest with the finest resolution (2.5 lp/mm).

Humans↗