3-D ultrasound imaging using a forward-looking CMUT ring array for intravascular/intracardiac applications

Area of Science:

• Biomedical Engineering
• Ultrasound Technology
• Medical Imaging

Background:

• Forward-viewing ring arrays offer potential for intravascular and intracardiac ultrasound applications.
• Capacitive micromachined ultrasonic transducers (CMUTs) are emerging as a viable technology for miniaturized ultrasound probes.

Purpose of the Study:

• To present volumetric ultrasound images generated by a novel forward-viewing CMUT ring array.
• To evaluate the imaging performance, including resolution and signal-to-noise ratio, of the CMUT array for intravascular applications.

Main Methods:

• A 2 mm diameter CMUT ring array with 64 elements (100 microm x 100 microm) was fabricated and wire-bonded to a custom integrated circuit.
• Phased-array imaging was performed in both conventional and collapse modes to assess fractional bandwidth, signal-to-noise ratio (SNR), and resolution.
• B-scans of a steel wire target and 3-D images of a stent were generated to demonstrate imaging capabilities.

Main Results:

• The CMUT array achieved 70% fractional bandwidth at 8.3 MHz (conventional mode) and 69% at 19 MHz (collapse mode).
• Measured SNR was 29 dB (conventional) and 35 dB (collapse mode).
• The 6 dB resolutions achieved were 189 microm (axial) and 0.112 radians (lateral) at 8 MHz, and 78 microm (axial) and 0.051 radians (lateral) at 19 MHz.

Conclusions:

• The forward-viewing CMUT ring array successfully generated high-quality, full-synthetic, volumetric ultrasound images.
• The demonstrated resolution and imaging quality are sufficient for practical intravascular and intracardiac applications.
• A reduced firing set enabled acceptable real-time imaging, highlighting the system's potential for clinical use.