Integrated System on a Chip for Guidewire IVUS

Although intravascular ultrasound (IVUS) provides real-time and high-resolution images of the arteries and it has become a significant imaging modality for cardiovascular interventions, its current implementations still have limitations in terms of accessing narrow and tortuous arteries. An IVUS system that can be realized on a guidewire can largely remedy these limitations. A significant aspect of guidewire IVUS is the integrated electronics. In this work, we present a practical integrated system-on-a-chip (SoC) for guidewire IVUS. The front-end circuitry has a 20-channel ultrasound transmitter (Tx) and receiver (Rx) array connected to a capacitive micromachined ultrasound transducer (CMUT) array. For communication between the front-end and back-end systems, an 8-channel flexible printed circuit (FPC) is used to meet the strict size requirements while presenting some challenges. To cancel the common noise, received signals are converted to the differential before being sent via the FPC. A 10 MHz sinewave is used as the clock source to reduce the crosstalk on the FPC which is recovered and frequency multiplied on-chip as the master clock. The SoC was fabricated in a 0.18 µm high voltage (HV) CMOS process, occupying a narrow active area of 0.3 mm × 3.6 mm and consuming 23.4 mW and 30.3 mW from LV and HV power supplies, respectively. The functionality of the integrated system-on-a-chip was verified by the CMUT/ASIC time domain test.