Three-dimensional acoustic impedance map analysis of soft tissue
Three-dimensional impedance maps (3DZMs) are virtual volumes of acoustic impedance values constructed from histology to represent tissue microstructure acoustically. From the 3DZM, the ultrasonic backscattered power spectrum can be predicted and model based scatterer properties, such as effective scatterer diameter (ESD), can be estimated. Additionally, the 3DZM can be exploited to visualize and identify possible scattering sites, which may aid in the development of more effective scattering models to better represent the ultrasonic interaction with underlying tissue microstructure. The 3DZM construction and analysis algorithms have been improved both in terms of performance and cost. A multiresolution registration scheme has been implemented in order to robustly reconstruct the 3DZM from real tissue. Additional processing, such as photometric correction and automatic detection of damaged histology sections, has been applied to ensure the reconstructed volume is faithful to the properties of the original tissue. In this work, 3DZMs were created from a set of human fibroadenoma samples. ESD estimates were made assuming a fluid-filled sphere form factor model from 3DZMs of volume 300x300x300 cubic microns. For a collection of 33 independent human fibroadenoma tissue samples, the ESD was estimated to be 111.4 plus/minus 40.7 microns. The 3DZMs were then investigated visually to identify possible scattering sources which conformed to the estimated model scatterer dimensions. Additionally, 3DZMs were compared with quantitative ultrasound (QUS) techniques. A chemically fixed section of rabbit liver was scanned ultrasonically, then used to create 3DZMs. ESD estimates were made using the fluid-filled sphere form factor. Twenty-four 3DZMs of volume 300x300x300 cubic microns were constructed from the sample, and using two methods of ESD estimation, produced ESD estimates of 93.6 plus/minus 52.7 and 7.04 plus/minus 1.30 microns. ESD was also estimated from ultrasonic backscatter using transducers with center frequencies 7.5, 13, 20, 40, and 65 MHz. The ESD estimates from the backscatter data were 102.2 plus/minus 30.5, 63.3 plus/minus 12.2, 23.6 plus/minus 26.2, 19.8 plus/minus 1.1, and 2.78 plus/minus 6.43 microns respectively. This work provides new insights into the 3DZM technique, both in terms of its viability for tissue studies and its relationship to more traditional QUS techniques.
Image Registration, Quantitative Ultrasound, Small-Scale Acoustic Scattering Models
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign