Graduate Thesis Or Dissertation

 

Liquid crystal thermography : a new system for breast cancer detection Öffentlichkeit Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/mp48sh80h

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  • A liquid crystal thermographic technique was developed for application to several problems in clinical medicine and physiology. The procedure was inexpensive, rapid, simple, versatile and acceptable to patients. Investigators in the past have used cholesteric liquid crystals for thermography but their use was limited to research in the medical field because the methods involved called for the direct spraying of the skin surface with the liquid crystals over a black paint. The present research has been involved in the development and fabrication of a liquid crystal dispersion thin film with very high elastomeric properties which provides perfect contact with the skin surface of a body of any configuration. Different films were prepared using plasticized vinyl resins in which the liquid crystals are dispersed. The final film yields optimum optical, thermal and mechanical characteristics and a long shelf life. Liquid crystal dispersions in plasticized polyvinyl chloride or copolymers of vinyl chloride and vinyl acetate were fabricated. However, polyvinyl butyral was selected since it forms strong, highly resilient films and yields optimum optical characteristics. After the film was perfected, a clinical comparative study was conducted to evaluate the new system. In this study, seventy-five volunteer women were given a breast examination using three modalities: (1) Liquid crystal thermography using the thin film. (2) Liquid crystal thermography using the direct spraying of the liquid crystals over a pre-blackened coat (Trade name--Lix Kit). (3) Infrared thermography using AGA Thermovision model 680 infrared thermography system. All positively read thermograms were followed up by a xeroradiography examination, the most recent and widely spread method for breast cancer detection. Positive thermographic signs were defined and a new interpretation scheme was introduced intended to reduce the false positive rate and to free the thermographic interpretation from the dependency on the experience of the reader. The new interpretation method was applied to one thousand random cases of patients who had breast examinations using infrared thermography, xeroradiography and pathological tests. This interpretation scheme is based on a trinary point system which penalizes each positive symptom by 1 or 2 points according to its severity. The total number of points which are assigned to the thermogram would make it negative, positive or equivocal. As a result of this method, the false positive rate which constitutes a major disadvantage of infrared thermographic techniques was reduced from 57.4% to 20.37%.
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