A Prototype System with Custom-Designed RX ICs for Contrast-Enhanced Ultrasound Imaging

This work presents a prototype system based on a multi-channel receiving (RX) integrated circuit (IC) for contrast-enhanced ultrasound (CEUS) imaging. The RX IC is implemented in a 40 nm low-voltage CMOS technology and is designed to interface to a capacitive micromachined ultrasonic transducer array. To enable a direct connection of the RX electronics to the transducer, an analog multiplexer with on-chip protection circuitry is developed. Stress tests confirm the reliability of this arrangement when combined with a high-voltage pulser. The RX IC is equipped with a highly programmable bandpass filter to capture harmonic signals from ultrasound contrast agents (UCAs), while suppressing fundamental components. In order to examine the impact of analog front-end bandpass filtering, in-vitro acoustic experiments are performed with UCAs. Spatial resolution analysis suggests that the analog front-end bandpass filtering combined with a pulse inversion (PI) technique can improve the lateral resolution by 38% or 9% compared to the original full-bandwidth approach or a stand-alone PI approach respectively, while the impact on axial resolution is negligible. A phantom study shows that compared to digital bandpass filtering, the analog front-end bandpass filtering enables a better use of the dynamic range of the RX electronics, resulting in better generalized contrast-to-noise ratio from 0.44/0.53 to 0.57/0.68 without or with PI.