Mirza Pasovic, François Varray, Olivier Basset, Christian Cachard
Aim of the study
Nonlinearity of the tissue distorts the US wave in propagation: Rise of higher harmonics and Energy of fundamental frequency is shifted to higher harmonics
Effects based on nonlinear ultrasound offer new possibilities for:
- Imaging nonlinear parameter B/A
- Tissue characterization
- Enhanced Ultrasound Contrast Imaging [bib]PASO-11[/bib]
Model
The model of non linear propagation is based on a KZK parabolic solution for unfocused transducer
a). | b). |
Methods and applications
1 - B/A imaging
In nonlinear contrast imaging, there is "competition" between 2nd harmonic generated by Ultrasound Contrast agent (UCA) and surrounding medium. To increase "Agent to Tissue Ratio", second harmonic generated by tissue must be reduced [bib]VARR-09[/bib].
2 - Frequency focalisation
Transmission of Second Harmonic Reduction Signal (SHRS) [bib]PASO-10[/bib]
a). | b). |
a) the initial time frequency image is diplayed, b) the resulting time frequency image is displayed after SHRS applications. The second harmonic component is completely reduced at the region of interest.