Ultrasound Tissue Displacement and Tissue Elasticity Imaging

This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. sectioning the original, beginning at the upper left-hand corner and continuing from left to right in equal sections with small overlaps. Each original is also photographed in one exposure and is included in reduced form at the back of the book. Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6" x 9" black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. In this dissertation, we investigate the feasibility of using high frequency ultrasound, to measure tissue motion and tissue elasticity for medical imaging applications. Ultra-sound provides a means for non-invasive imaging of soft tissues, providing soft tissue contrast that can not be achieved using conventional X-ray or tomographic imaging. A two-dimensional correlation search algorithm is used to track local tissue displacements from radio frequency (RF) ultrasound echoes and from digitized ultrasound images. The accuracy of displacement imaging is investigated as a function of various imaging parameters such as ultrasound frequency and target size. Ultrasound elasticity imaging consists of three basic steps: 1) measurement of tissue displacement, 2) estimation of tissue stresses and strains, and 3) recovery of tissue elasticity. Tissue strains and tissue elasticities are obtained from reconstructed tissue displacement fields and experimental measurements of applied stresses. Ultrasound elasticity measurements were compared with independent Instron load cell elasticity measurements. Several examples of tissue displacement imaging of breast tumors in human breast cancer patients and ultrasound elasticity measurements of tissue phantoms (soft gels), and samples of bovine muscle and fat tissue are provided. iii ACKNOWLEDGMENTS Special acknowledgment to Dr. Ron Adler who helped tremendously with acquisition of clinical data and provided useful suggestions. He …