The objective of the proposed research is to investigate and develop high-performance ASIC and ADC prototypes under practical constraints for emerging ultrasound imaging system-on-a-chip (SoC). Although ultrasound imaging systems are widely adopted to assist diagnosis and guide treatment since they can be portable and provide real-time images, they still face limitations in real-life applications, such as accessing narrow and tortuous arteries, providing real-time, high-framerate, and high-resolution images, communicating robustly and efficiently, etc.Two directions would be explored in the proposed work to mitigate these constraints. One direction focuses on miniaturization and integration of the front-end ASIC. Targeted for intravascular ultrasound (IVUS), two integrated SoCs for guidewire ultrasound imaging systems have been designed and fabricated. The presented approaches are equally applicable in other miniature probes, such as intracardiac echography (ICE) catheters. The transmit micro-beamforming technique has also been implemented on-chip to steer the acoustic wave and further increase the SNR without losing the framerate. The other direction focuses on high-performance ADC and communication. A noise coupling (NC) voltage-controlled oscillator (VCO)-based sigma-delta ADC has been developed for low-frequency, high-resolution on-chip data conversion, and its transistor-level design is almost completed. A space-time compressed sensing framework for full-channel RF data acquisition is also proposed for multi-model, high-resolution, high-framerate ultrasound imaging in low-power integrated SoC.