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© 2011 Alexander D. Pawlicki THREE-DIMENSIONAL IMPEDANCE MAP ANALYSIS OF BIOLOGICAL TISSUE TO ELUCIDATE SMALL-SCALE ACOUSTIC SCATTERING BEHAVIOR BY ALEXANDER D. PAWLICKI THESIS

Three-dimensional impedance maps (3DZMs) are computational models of acoustic impedance of tissue constructed from a series of adjacent histology images. The power spectrum of a 3DZM can be analyzed to estimate model-based quantitative ultrasound parameters such as effective scatterer diameter (ESD) and effective acoustic concentration (EAC). The goal in this approach is to determine a link between the quantitative ultrasound estimates made from tissue and actual tissue structures seen in histology as a means of identifying the ultrasonic scattering sites in different types of tissue. The 3DZM construction and analysis routines have been updated in order to increase speed and overall performance. In particular, the map creation algorithm was structured in a parallel implementation to greatly increase speed. The ESD analysis algorithm was modified to increase both speed and accuracy, and an EAC estimator has been implemented also. The new analysis algorithm was tested through simulating 3DZMs and was found to be very accurate for estimating ESD, but only accurate up to an offset for EAC. The 3DZM method was then applied to rabbit liver and rat cervix tissue. ESD estimates for both normal and fatty rabbit liver were made with average values of 7.5 ± 1.3 µm and 7.0 ± 0.3 µm, respectively. This size was identified to be very near that of a cell nucleus. ESD estimates of the rat cervix tissue had an average value of 11.3 ± 3.1 µm. This size did not correspond to any readily apparent structures in the tissue but fell within the range of estimates made from real ultrasound data. This work seeks to evaluate and improve upon the previous work of the 3DZM method.