Annular-ring CMUT arrays for forward-looking IVUS: transducer characterization and imaging

Area of Science:

• Medical Imaging
• Ultrasound Technology
• Microsystems Engineering

Background:

• Intravascular ultrasound (IVUS) imaging requires high-resolution transducers for visualizing arterial structures.
• Capacitive micromachined ultrasonic transducers (CMUTs) offer miniaturization and integration potential for medical devices.
• CMUT arrays fabricated with low-temperature, CMOS-compatible processes are desirable for single-chip integration.

Purpose of the Study:

• To characterize a 64-element annular-ring CMUT array for forward-looking IVUS imaging.
• To evaluate the performance of the CMUT array in terms of imaging capabilities and signal-to-noise ratio (SNR).
• To validate developed modeling tools for designing future IVUS CMUT arrays.

Main Methods:

• Fabrication of a 1.15-mm diameter annular-ring CMUT array using low-temperature, CMOS-compatible processes.
• Characterization of the array's radiation pattern and pulse-echo performance at a 15-MHz center frequency.
• Acquisition of RF A-scan data for imaging and SNR measurements using a 32-element configuration.
• Comparison of experimental point spread functions with simulated and theoretical array responses.

Main Results:

• The CMUT array element exhibited a 40-degree view angle for forward-looking imaging at 15 MHz, consistent with theoretical models.
• Pulse-echo measurements demonstrated a -10-dB fractional bandwidth of 104% around 17 MHz for wire targets.
• Experimental and simulated array responses, including point spread functions, showed good agreement.
• The developed modeling tools accurately predicted array performance.

Conclusions:

• Annular-ring CMUT arrays fabricated with CMOS-compatible processes are viable for forward-looking IVUS imaging.
• The study validates the use of CMUTs for miniaturized, high-performance IVUS systems.
• The developed modeling framework is effective for designing and optimizing future IVUS CMUT arrays.