Investigation of Classical Pulse Sequences for Contrast-Enhanced Ultrasound Imaging With a cMUT Probe

Capacitive micromachined ultrasonic transducers (cMUTs) provide promising ultrasonic technology that could become an alternative to piezoelectric probes for medical applications. cMUTs could be very valuable for contrast-enhanced ultrasound imaging based on higher harmonics detection. However, their use is restricted by the intrinsic nonlinearity of the cMUT transmitters themselves, because it is difficult to distinguish between the nonlinearity of the microbubbles and the nonlinearity arising from the emitting transducer. A number of approaches have been proposed in recent years to cancel the nonlinearity of cMUTs. However, these techniques have limitations in terms of implementation with current ultrasound scanner electronics. The solution to be comparable with classical methods should not need precharacterization of the probe or changing the bias voltage (amplitude or polarity) but does need good sensitivity and a high frame rate to avoid motion artifacts. We propose here proof of a concept of an adapted amplitude modulation sequence with cMUT where transmit elements operate alternately. We show that this method, which is currently used with piezoelectric probes, is fully applicable to cMUT probes and the intrinsic nonlinearity of the transmitter is no longer an issue.