Amplitude modulated pulse inversion technique for high SNR of tissue harmonic imaging using CMUT

Capacitive micro-machined ultrasonic transducer (CMUT) has various advantages in superior imaging quality and circuit integration capability compared with piezoelectric transducer. One of major challenges for CMUT is to perform tissue harmonic imaging (THI) that is widely used in clinical practice because it is difficult to obtain enough because of low signal-to-noise ratio (SNR) due to CMUT fs intrinsic nonlinear behavior. Conventional pulse inversion (PI) uses inverted transmit pulse pair with equal amplitude between the first (TX1) and the second pulse (TX2). Such inverted pulse is not practical for CMUTs due to the asymmetric transmission performance caused by the offset of initial membrane position of membrane. Although amplitude modulation (AM) technique has been proposed (Tanaka et al. IUS 2015) for THI using CMUT, the extracted harmonic signal lacks SNR for practical use. Here, we propose a novel technique that realizes high SNR under the restriction of nonlinear asymmetric behavior of CMUT.