7.5 MHz dual-layer transducer array for 3-D rectilinear imaging.

Area of Science:

• Biomedical Engineering
• Medical Imaging
• Materials Science

Background:

• Fabrication and interconnection challenges limit large-element 2-D ultrasound transducer arrays.
• Previous work introduced a 5 MHz dual-layer transducer for 3-D rectilinear imaging, reducing complexity.
• Higher frequencies are crucial for clinical imaging of superficial tissues.

Purpose of the Study:

• To present a 7.5 MHz dual-layer transducer array for 3-D rectilinear imaging.
• To address limitations in fabricating large-element 2-D ultrasound arrays.
• To enhance imaging of superficial anatomical structures.

Main Methods:

• Designed and fabricated a modified acoustic stack model for a 7.5 MHz dual-layer transducer.
• Employed sub-dicing of PZT elements to create a 2-2 composite, improving sensitivity and bandwidth.
• Acquired full synthetic-aperture 3-D ultrasound data using a Verasonics data-acquisition system (VDAS) and performed offline 3-D beamforming.

Main Results:

• Achieved a measured -6 dB fractional bandwidth of 71% at a 7.5 MHz center frequency.
• Measured lateral beamwidths of 0.521 mm (azimuth) and 0.482 mm (elevation), closely matching simulations (0.43 mm).
• Successfully visualized multiwire and cyst phantoms using 3-D beamforming, with contrast enhancement in cyst images via generalized coherence factor (GCF).

Conclusions:

• The developed 7.5 MHz dual-layer transducer array is suitable for 3-D rectilinear imaging.
• Sub-dicing PZT elements enhances transducer performance, enabling more feasible 3-D ultrasound.
• This technology advances high-resolution 3-D imaging for clinical applications like breast and musculoskeletal imaging.