Fabrication and performance of a miniaturized 64-element high-frequency endoscopic phased array

Area of Science:

• Ultrasound technology
• Medical imaging
• Materials science

Background:

• Miniaturization of ultrasound transducers is crucial for advanced endoscopic imaging.
• Phased-array technology enables beam steering for flexible imaging.
• High-frequency ultrasound offers improved resolution for delicate structures.

Purpose of the Study:

• To develop a compact, high-frequency phased-array ultrasound transducer for endoscopic applications.
• To evaluate the imaging performance and resolution of the novel transducer design.
• To demonstrate the feasibility of generating real-time ultrasound images with the developed probe.

Main Methods:

• Fabrication of a 40-MHz, 64-element phased-array transducer using PMN-32%PT single-crystal and novel wire-bonding techniques.
• Implementation of a semi-kerfed design with partial dicing for improved element directivity.
• Integration of a P(VDF-TrFE) matching layer and TPX lens for passive elevation focusing.
• Characterization of array performance including bandwidth, electromechanical coupling, and directivity.
• Acquisition and offline processing of RF data using a reprogrammed imaging platform to generate sector images.

Main Results:

• Achieved a 2.5 x 3.1 mm endoscopic form factor with a 40-MHz, 64-element phased-array transducer.
• Measured a two-way -6-dB pulse bandwidth of 55% and an average electromechanical coupling (k(eff)) of 0.62.
• Demonstrated one-way -6-dB directivities of ±20°, an improvement over kerfless designs.
• Obtained a lateral resolution of 80 µm at a 0° steering angle and an elevation focus of 152 µm.
• Successfully generated ex vivo ultrasound images of porcine brain tissue with a 60 dB dynamic range.

Conclusions:

• The developed miniaturized phased-array transducer meets the requirements for high-resolution endoscopic ultrasound imaging.
• Novel fabrication techniques enabled significant size reduction and performance enhancement.
• The transducer's capabilities were validated through phantom and ex vivo tissue imaging, showing potential for clinical applications.