5F-2 Analysis of Acoustic Interaction Effects and Crosstalk in CMUT Linear Arrays for Medical Imaging

Acoustic interactions occur between the membranes of capacitive micromachined ultrasonic transducers (CMUTs) in liquid-coupled operation, resulting in the excitation of spurious modes with a degradation of the output pressure. In pulse-echo operation of CMUT linear arrays for medical imaging, the acoustic interaction effects manifest as oscillation tails straight after the pulse signal and the echo signal. On the other hand, such oscillations can be observed in the frequency spectra as ripples within the operational bandwidth of the transducer, thus contributing to the cross-talk in CMUT arrays. The cross-talk is detrimental to the quality of the reconstructed image. In this work, the acoustic interaction effects are analyzed through finite element modeling (FEM) and experimental measurements carried out with 128-elements CMUT arrays. An index, the acoustic interaction level (AIL), is introduced to quantify the cross-talk in the actual B-mode pulse-echo imaging operation of a CMUT linear array. The experimental AIL is found approximately -42 dB for the echoes returned from a planar reflector in a single line of view of the reconstructed image