An optimized mismatched filter for continuous emission ultrasound imaging

Current pulse-echo ultrasound imaging techniques provide direct insight into tissue structures but face two key limitations: an upper bounded imaging framerate and an inability to capture phenomena during most of the acquisition time due to a small duty cycle and a short wave-tissue interaction duration. To address these issues, we proposed continuous emission ultrasound imaging (CEUI), demonstrated for motion-mode imaging with a single-input-single-output device. CEUI relies on the continuous transmission of an encoded signal, requiring decoding upon reception. Initial evaluations of pulse compression approaches revealed a critical limitation: interference from other emission segments during decoding, causing image quality loss. This paper introduces a mismatched filter designed to reduce integrated sidelobe ratio (ISLR) of a specific point spread function of the imaging system. The latter incorporates the impact of emission segments that interfere on a single decoding step. Simulation results show a significant enhancement of the ISLR by 7 dB compared to the matched filter and 5.5 dB compared to classical mismatched filter, while reducing the mainlobe width by 60 % and respectively 25 %.