SNR Improvement by Subharmonic Extraction with Hammerstein Models for Microbubble Signals

Sébastien Ménigot (1) , Emma Kanbar (1) , Ayache Bouakaz (1) , Jean-Marc Girault (1)

1 iBraiN - Imaging, Brain & Neuropsychiatry

Nowadays, ultrasound imaging contrast has enhanced the contrast thanks to the nonlinear behaviour of microbubbles. Unfortunately, this contrast improvement is compromised by the nonlinear acoustic propagation in tissue. Fortunately, microbubbles can also oscillate with a f0/2-subharmonic frequency. Therefore, as there is no subharmonic in the tissue backscattering, the subharmonic imaging could increase the contrast highly. However, the subharmonic extraction can be more or less empirical by using standard filters. The aim of this study is thus to propose an optimal extraction of subharmonics. As Hammerstein model fits well the nonlinear systems with harmonics, we propose two solutions based on a combination of such a model to fit nonlinear systems with sub and ultra-harmonics. Experiments are carried out by transmitting ultrasound wave at 10 MHz to a water-diluted solution of Sonovue. The nonlinear microbubble responses were measured by a 5 MHz transducer. Results showed that the error between the experimental signal and the modeling signal was less than -18 dB. Moreover, the bias was always less than -15 dB. Finally, the signal-to-noise ratio could be increase by 4 dB in comparison with a standard filtering. Thanks to the modified Hammerstein model, it was possible to set the extraction optimally adjusted to the subharmonic components. No manual analysis of the signals was required.

Mots clés: subharmonic extraction; Hammerstein model; Signal processing

Domaines: Traitement du signal et de l'image [eess.SP]; Acoustique [physics.class-ph]; Imagerie

Sébastien Ménigot, Emma Kanbar, Ayache Bouakaz, Jean-Marc Girault. SNR Improvement by Subharmonic Extraction with Hammerstein Models for Microbubble Signals. IEEE International Ultrasonic Symposium 2016, IEEE UFFC, Sep 2016, Tours, France. ⟨10.1109/ULTSYM.2016.7728740⟩. ⟨hal-01371261⟩