Image and Signal Analysis for Medical Applications for Terahertz Frequency Imaging

• Main Author: Reed, Sadie
• Published: University of Leeds 2007
• Subjects: 615.84
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485595

Terahertz pulsed imaging is a relatively new modality compared with the established techniques, and most research in this area is still in the preliminary stage. This thesis aims to present results taken on measurements from the frequency spectrum of the terahertz time domain pulse. Primarily an analysis was performed on one tooth and one step wedge to investigate the boundary artefacts seen at each frequency available in the terahertz pulse.. This was later extended to five teeth and three step wedges and presence of these·anomalies was then explained using recognised theoretical equations and a hypothesis to predict the further occurrence of these artefacts proposed. The results demonstrated a good agreement when the line profile and region of interest measurements were used to determine the frequency minima. In the cases where minima were not detected, a limiting criterion was determined using the parameters from which the expected theory is reliant. The study was expanded further by the design and implantation of specificalIy designed phantoms that assessed the capabilities of the terahertz system. Successful measurements with good agreement to the theory were obtained for the phantoms and those that were immeasurable fell outside the limiting criteria. This technique has highlighted a method of analysing changes in refractive index and thickness between the boundaries of a sample, and with further study could lead to a successful terahertz pulsed imaging application.