Enhancement of photoacoustic imaging quality by using CMUT technology: Experimental study

Photoacoustic (PA) signals are known to be wideband thanks to their N-shape. Yet ultrasound (US) transducers commonly used for PA imaging use piezoelectric technology (PZT) and hence present a limited bandwidth in reception. Thus, PA signals can not be fully acquired and are filtered by the receiver. Capacitive micromachined ultrasonic transducer (cMUT) technology has emerged as an alternative to conventional PZT transducers in the field of medical imaging. Among the interesting properties offered by this technology, a theoretically infinite bandwidth in reception may be reached. In this work the interest of cMUT larger bandwidth for PA imaging is studied by comparing a cMUT and a classical PZT linear US probes. PA acquisitions have been made on several homemade bimodal phantoms whose properties are well-known. For each phantom, acquisitions have been realized with both probes in the same conditions. The probes characteristics have been verified for the reception of PA signals and three criteria have been evaluated to compare the two probes: signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and the maximal amplitude of PA signals. The cMUT probe presents indeed a larger fractional bandwidth in reception and the SNR and CNR are enhanced by at least 6dB. Furthermore, the sensitivity of the cMUT probe is higher and it receives 4 to 5 times more signal than the PZT probe. Therefore, this work highlights the potential of cMUT technology for PA imaging through quantitative as well as qualitative parameters.