Dissertation submitted in full compliance with the requirements for the Master's degree in Technology: Radiography, Durban Institute of Technology, Durban, 2004. / The object of this study was to use Transvaginal ultrasound to evaluate the thickness of the endometrium to exclude endometrial abnormality in Black South African women with postmenopausal uterine bleeding. Transvaginal ultrasound is an excellent diagnostic method for assessing endometrial pathology. The study was carried out at the Gynaecological Ultrasound Department, King Edward VIII Hospital. The study included 76 Black women with postmenopausal uterine bleeding. The thickness of the endometrium was measured by Transvaginal ultrasound. The measurement included both endometrial layers (double-layer technique). The Transvaginal ultrasound measurement was compared with the histopathological diagnosis of the biopsy specimens. At the end of the investigation, findings obtained were 3.9% non-representative, 44.8% endometrial adenocarcinomas, 14.5% benign polyp, 3.9% chronic Endometritis, 17.1% benign endometrium, 5.3% endometrial hyperplasia, 9.2% atrophic endometrium, 3.9% myometrial invasion and 1.3% Malignant Mixed Mullerian Tumour. In this study, the thickness of the endometrial echo varied from 5mm to 35mm, with a mean of 18,2mm. When the thickness of the endometrial echo was compared with the histopathological results, the mean value for non-representative was 7.83mm, much lower than the thickness of an active endometrium (13.25mm). In cases with atrophic endometrium, the thickness ranged from 6mm to 30mm with a mean of 15.86mm. The mean value obtained for cases with endometrial adenocarcinoma was 20.32mm (range 11 to 35mm). The sensitivity, specificity and accuracy of Transvaginal ultrasound for detecting endometrial malignancy were 100% if the cutoff limit of 4mm was used In conclusion, this study using Transvaginal ultrasound demonstrated that a thickness limit greater than 8mm was considered in detecting malignancy. No malignant endometrium was thinner than 5mm. Therefore in women with postmenopausal uterine bleeding and an endometrium less than 4mm, it may be justified not to perform further investigations. Transvaginal ultrasound is a simple, well-tolerated safe and reliable method for identifying endometrial thickness in postmenopausal Black South African women. / M

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Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 172-185).

Ultrasonic attenuation is a useful tool in characterizing the damage state of different materials. The attenuation coefficients for the incident longitudinal and transverse waves are both derived from the scattering cross section of the material. Scattering cross section is defined as the ratio of the scattered energy to the incident energy. The incident wave field can be scattered at inclusions, voids and material defects; there is also grain boundary scattering in polycrystalline materials. For accurate material characterization, it is important to distinguish between the different types of scattering and to relate the attenuation to its appropriate source. This study first solves the single scatterer problem using either the Born approximation (for difficult scatterer shapes and for anisotropic scatterers), or the exact solution (in cases where it is necessary to provide an accurate description of the viscoelastic behavior of the surrounding effective medium). Multiple scattering effects are investigated by a differential self-consistent scheme and a self-consistent scheme. Both multiple scattering approaches are applicable for each single scatterer solution. The differential self-consistent scheme describes the scattering cross section dependent on the volume fraction of the scatterers, and is restricted to low volume fractions and materials, where the surrounding material is clearly distinguished from the inclusions. The self-consistent scheme is applicable to high volume fractions of inclusions as well as to polycrystalline materials, where the distinction between surrounding material and inclusions is not possible.

No description available.

This research aims to develop a method to evaluate the deterioration of the tube material within a boiler, in order to reduce the failure of it. In this thesis, natural frequency measurement method and ultrasonic attenuation method are mainly applied, and it has reached to a conclusion that the ultrasonic attenuation method is more reliable. Traditionally, the inspectors used the ultrasonic thickness measurement machine to evaluate the thickness and track the condition of a boiler. However, besides the thickness, the inspectors could not have clear understanding of the material and situation within a boiler. To improve the inspection effectiveness, the researcher measures the natural frequencies of the tube material in the new and old boilers by using natural frequency measurement. They found that the used tube material has been altered due to the difference between the natural frequencies. The ultrasonic attenuation conditions of the tubes are also evaluated in this thesis. The echoes of the ultrasound propagating through the thickness of the tube can be analyzed by relative comparison and absolute comparison, respectively. The relative comparison compares the echoes of the multiple back reflections of the ultrasound between the tubes of old and new boilers. In addition, the absolute comparison analyzes the amplitude of the echoes of the ultrasonic multiple back reflection to calculate the ultrasonic attenuation of the tube. Besides the two major techniques, the material analysis, metallurgical analysis, internally scale analysis and mechanical property evaluation are also applied in this thesis to help developing a method to evaluate the deterioration of the tube material within a boiler. This research demonstrates that the ultrasonic attenuation measuring methods can offer reliable results to evaluate the quality of the boiler.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI Company.