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Biomedical subjects

L S Wilson

Publications and source records attributed to L S Wilson.

35 records · Page 2Linked to original sources
PubMed1987

Evaluation of ultrasonic attenuation in diffuse diseases of spleen and liver.

Ultrasonic attenuation has been measured using frequency domain signal processing in clinical trials of patients with liver and spleen diseases. By comparing the variance encountered in local measurements and in measurements at a number of adjoining sites, the need for averaging over large volumes of tissue to avoid the effects of large fluctuations is established. In spleens of patients with myelofibrosis, no correlation between fibrosis and attenuation was found. However it was found that variations in splenic volume were accompanied by inverse changes in attenuation, most likely due to blood pooling. A correlation was found between splenic blood flow per unit organ volume and attenuation. In cirrhotic livers, attenuation was significantly increased with fatty infiltration, but only slightly increased in livers containing minimal fat. These findings tend to reduce the probability of finding successful clinical applications for attenuation slope measurements.

Fatty Liver↗
PubMed1984

Frequency domain processing for ultrasonic attenuation measurement in liver.

A frequency domain signal processing scheme is developed for measuring attenuation and attenuation slope in vivo, using equally spaced depth samples and linear regression techniques. The algorithm may be expressed in terms of linear, commuting operators acting on an array of log power spectra. By interchanging operators, a computationally efficient scheme may be developed, and the accuracy of the result assessed in terms of tissue uniformity and frequency linearity. Corresponding algorithms are demonstrated for measurement of attenuation at particular frequencies and attenuation in focal lesions. Measurements have been made using an Octoson water-delay echoscope on both normal and pathological livers. Variation of attenuation with a number of disease states has been found.

Colonic Neoplasms↗
PubMed1984

Beam pattern (diffraction) correction for ultrasonic attenuation measurement.

The measurement of tissue attenuation from pulse-echo data has been widely investigated. This paper examines correction of the measurements for the effect of the transducer beam. Computer and experimental studies are performed on a number of reflectors including smooth and rough planes, ideal point scatterers, T.M. material and liver and spleen tissue. It is shown that the corrections obtained from T.M. phantom material differ from those obtained using in vivo tissue as the reflector and corrections for liver and spleen differ markedly. Comment is made on the possibility of using "beam correction" itself as a tissue characterization parameter.

Acoustics↗
PubMed1983

Fibrosarcoma of the penis: case report and review of the literature.

We report a case of fibrosarcoma of the penis and review the literature. We believe that amputation is the most effective therapy and the role of lymphadenectomy is equivocal. All cases should be reported to better define the roles of various oncologic modalities of therapy.

Aged↗
PubMed1983

The influence of fiscal incentives on interregional migration: Canada 1961-78.

The authors "estimate interprovincial migration models for Canada with special emphasis on determining the importance of fiscal variables as inducements to migrate. This is important because of suggestions that fiscal surpluses may cause inefficient migration. There may be too little migration out of the maritimes because of federal transfers and there may be too much migration into the western provinces as a result of large resource rents." (summary in FRE)

Americas↗
PubMed1982

Measurement of velocity of propagation from ultrasonic pulse-echo data.

A method is proposed for determining velocity of propagation of ultrasound in tissue by processing the pulse-echo data obtained from a compound scan. Individual sectors from different transducer positions are reconstructed and a suitable area common to the two sectors is selected. Cross-correlation of the region of interest is used to detect an apparent shift in the image due to refractive effects. The refractive effects are analysed by a ray-tracing procedure to determine an effective velocity within the tissue. The system has been tested using the U.I. Octoson as input device and both model targets with known velocity of propagation and in vivo liver tissue. The accuracy in the model experiment was +/- 5 ms-1 while the repeatability of measurements in tissue was +/- 15 ms-1. techniques for extending the method to multiple region systems are suggested.

Abdomen↗
PubMed1981

Shadowing and enhancement in ultrasonic echograms by reflection and refraction.

The action of reflection and refraction in producing shadows and enhancement in ultrasonic echograms behind cystic structures is well known, but the physical explanations usually used are incomplete. In this paper the emergent beam patterns for a number of cases are plotted and this data used to explain the shadows and enhancement observed. Cases are also illustrated of echoes displayed incorrectly within the shadow region and of reflectors within the shadow region displayed elsewhere. The use of the echographic appearances to assess the velocity of propagation in cystic structures is described.

Image Enhancement↗
PubMed1981

Decreased number of glucocorticoid receptors in dermal fibroblasts from individuals with facial clefting: a preliminary report.

Glucocorticoids are potent inducers of cleft palate in various laboratory animals. Recent work has demonstrated that the susceptibility of mice to the teratogenic action of glucocorticoids is strongly correlated with the number of fetal receptors for glucocorticoids. In the present study we have investigated whether there is a difference in levels of glucocorticoid receptors between individuals with or without cleft lip +/- cleft palate or isolated cleft palate. We have found that dermal fibroblasts from the affected individuals have significantly fewer glucocorticoid receptors than do fibroblasts from unaffected persons. This decrease in receptors may reflect a basic hormonal defect in these individuals, which presumably could play a role in the etiology of facial clefting.

Adolescent↗
PubMedDate not supplied

Knowledge-based method for segmentation and analysis of lung boundaries in chest X-ray images.

We present a knowledge-based approach to segmentation and analysis of the lung boundaries in chest X-rays. Image edges are matched to an anatomical model of the lung boundary using parametric features. A modular system architecture was developed which incorporates the model, image processing routines, an inference engine and a blackboard. Edges associated with the lung boundary are automatically identified and abnormal features are reported. In preliminary testing on 14 images for a set of 18 detectable abnormalities, the system showed a sensitivity of 88% and a specificity of 95% when compared with assessment by an experienced radiologist.

Algorithms↗
PubMedDate not supplied

Longitudinal assessment of economic burden and clinical outcomes in acromegaly.

OBJECTIVE: To determine costs and outcomes over time for surgical and various medical regimens in the management of patients with acromegaly. METHODS: We studied a sample of 53 consecutive Canadian patients with acromegaly who underwent a transsphenoidal pituitary surgical procedure only (N = 27) or in conjunction with medical therapy (N = 26). Outcomes were analyzed as person-months spent in various health state outcomes, which were defined on the basis of growth hormone and insulin-like growth factor I levels. Costs are reported in 1998 Canadian dollars. RESULTS: The mean duration of follow-up was 49 months. Of the 53 patients, 25 (47%) had microadenomas at admission. Patients spent as much as 65% of the time in "uncured" health states. Patients with less extensive disease had better outcomes. The mean annual cost per patient was $8,111 (95% confidence interval, $5,848 to $10,374). Medications were the largest contributor to overall cost (38%). Although per patient surgical costs themselves were high (ranging from approximately $2,800 to $9,200), when averaged over the 4 years the mean annual cost was approximately $2,400, less than the cost of medications. Treatment of macroadenomas cost more than treatment of microadenomas ($11,425 versus $4,442 annually). The treatment of acromegaly costs $14.7 million annually in Canada (95% confidence interval, $10.6 to $18.8 million) and, if patterns of care are similar, about $139 million annually in the United States. CONCLUSION: Treatment of acromegaly is no more costly than therapy for other chronic diseases, especially those with a surgical component. Early diagnosis (at the stage of microadenoma) resulted in better outcomes and lower costs. Thus, from the standpoint of economics and well-being, a continued aggressive attitude toward screening programs and treatment of persistently active acromegaly seems warranted.

Acromegaly↗