Quantitative ultrasound techniques have been previously used to evaluate biological hard tissues, characterized by a large acoustic impedance contrast. Here, we are interested in the imaging of experimental data from different test-targets with high acoustic impedance contrast, using the Full Waveform Inversion (FWI) method to solve the inverse problem. This method is based on high-resolution numerical modeling of the forward problem of interaction between waves and medium, considering the full time series. To reduce the complexity of the numerical implementation, the model considers a fluid medium. Therefore, the aim is to evaluate the precision of the reconstruction under this assumption for materials with a different level of attenuation of shear waves, to study the limits of this hypothesis. Images of the sound speed obtained using the experimental data are presented, and the precision of the reconstruction is evaluated. Future work should include viscoelastic materials.

Medical B-mode ultrasound is widely used for the examination of children’s limbs, including soft tissue, muscle, and bone. However, for the accurate examination of the bone only, it is often replaced by more restrictive clinical modalities. Several authors have investigated ultrasonic imaging of bone to assess cortical thickness and/or to estimate the wave velocity through the internal structure. The present work focuses on the transverse slice imaging process using reflection-mode ultrasound computed tomography (USCT). The method is valid for imaging soft tissues with similar acoustic impedances, but in the presence of bone, the higher contrasts alter the propagation of ultrasonic waves and reduce the contrast-to-noise ratio (CNR). There is a need to change the methods used for the processing of ultrasonic signals. Our group has developed a wavelet-based coded excitation (WCE) method to process information in frequency and time. The objective of this study is to use the method to improve reflection-mode USCT, at low ultrasonic intensities, to better address organ morphometry. Experimental results on a newborn arm phantom and on an ex vivo chicken drumstick are presented, and the usefulness of this WCE-mode USCT is discussed.

No abstract