Quantitative Ultrasound Techniques To Characterize Soft Tissue Anisotropy

Quantitative ultrasound techniques based on the parameterization of the backscatter coefficient (BSC) generally assume that the tissue under investigation is homogeneous and isotropic. However, some tissues such as flowing red blood cell (RBC) aggregates, myocardium or bicep muscles exhibit angle-dependent acoustic properties (BSC and/or attenuation coefficient). The objective of this thesis was to incorporate anisotropy in tissue backscatter analysis. First, an ultrasonic backscattering model is proposed and evaluated numerically to characterize the anisotropic structures of RBC aggregates. Then, an experimental procedure was evaluated to measure BSC anisotropy in tissue-mimicking phantoms. More specifically, a performance comparison is carried out between a capacitive micromachined ultrasonic transducer probe and a commercial piezoelectric probe to measure backscatter anisotropy by using the focused beam steering imaging strategy.