Harmonic imaging, based on the propagated medium nonlinearity, is a clinical imaging technique
which increases the resolution of ultrasound images. The ultrasound measure of the local nonlinear
parameter brings new perspectives in term tissues characterization. However, access to this
information suffers from two strong points: from one hand, there is no current measurement method
of this parameter in echo mode configuration and on the other hand, the simulation tools taking into
account the nonlinearity are not many developed.
An angular spectrum method has been proposed to compute the nonlinear pressure field with
inhomogeneous nonlinear parameter. This pressure field is then used to generate ultrasound images
containing the harmonic component. This spectral approach has been implemented on a GPU in
order to accelerate the computation and package in a free software made available to the scientific
community under the name CREANUIS.
In a second time, a extension of a comparative method (ECM) has been proposed to take into
account media with inhomogeneous nonlinearity, working an echo mode configuration. Thanks the
developed simulation tools, different configurations have been used to parameterize and to evaluate
the ECM which has then be validated on test objects and in vitro animal’s livers. Even if the
measure presents a relatively weak resolution, the obtained images demonstrated a high potential in
the nonlinear parameter imaging of tissues.