Improved FL-IVUS imaging with low voltage single-chip CMUT-on-CMOS array using temporally coded excitation

Synthetic phased array based high frequency imaging devices on catheter probes suffer from low SNR and limited penetration due to small active transducer area and frequency-dependent tissue attenuation. Although using signal averaging improves the SNR, it increases data collection time which degrades real time imaging performance. Temporally coded pulses emit high energy to the imaging medium and enhance SNR, using a suitable decoding procedure, without compromising frame rate. We previously demonstrated the volumetric imaging performance of a single-chip forward looking CMUT-on-CMOS system. In this study, we describe the implementation of temporal coding excitation in our single-chip system with reduced DC voltage levels and present the imaging results. A 2-cycle 13-bit Barker code was generated to encode a rectangular unipolar pulse waveform. 24-ns pulse width was chosen for maximum energy transfer to the system. Due to the limitation of internal pulsers, a 25-V pulse amplitude was used to produce the encoded excitation signal. The received signals were decoded by using spectrum inversion filtering. Imaging experiments were performed using a pig artery phantom immersed in water. The reconstructed 2D cross-sectional images using coded excitation produces 9 dB improvement in image SNR compared to single pulse excitation without any frame rate degradation.