A 30-MHz, 3-D Imaging, Forward-Looking Miniature Endoscope Based on a 128-Element Relaxor Array

Area of Science:

• Biomedical Engineering
• Materials Science
• Medical Imaging

Background:

• 3-D ultrasound imaging faces challenges in probe fabrication and miniaturization.
• Crossed electrode arrays reduce element count (2N vs. N^2) but pose packaging difficulties for endoscopic applications.

Purpose of the Study:

• To design, fabricate, and characterize a 128-element crossed electrode array for miniature endoscopic 3-D ultrasound.
• To overcome practical challenges in integrating high-frequency arrays into small endoscopic form factors.

Main Methods:

• Developed a novel fabrication process using a thinly diced flex circuit for back-side connections, enabling a 2.5 mm endoscope size.
• Utilized an electrostrictive ceramic composite and laser dicing for array fabrication and electrode patterning.
• Applied a vacuum-deposited Parylene matching layer and characterized electrical impedance, bandwidth, and crosstalk.

Main Results:

• Achieved an electrical impedance magnitude of 49 Ω with a -55.5° phase angle on resonance.
• Demonstrated array elements with a -6-dB two-way bandwidth of 60% at a 34-MHz center frequency.
• Measured average crosstalk of -37 dB (nearest neighbor) and -29 dB (next nearest neighbor), with confirmed pulse polarity and fast switching.

Conclusions:

• Successfully fabricated and characterized a miniature endoscopic crossed electrode array suitable for real-time 3-D ultrasound.
• Preliminary 3-D images of a wire phantom were generated using the simultaneous azimuth and Fresnel elevation (SAFE) compounding technique.