An 8 mm endoscopic histotripsy array with integrated high-resolution ultrasound imaging

Area of Science:

• Medical Devices
• Acoustic Engineering
• Biomedical Ultrasound

Background:

• Histotripsy offers non-invasive tissue ablation by generating cavitation bubbles.
• Existing histotripsy systems often use lens-focused transducers, which have limitations in depth-of-field and electronic steering.
• Image-guided systems are crucial for precise targeting and monitoring of ablation procedures.

Purpose of the Study:

• To fabricate and characterize an 8 mm diameter, image-guided, annular array histotripsy transducer.
• To compare the performance of the developed annular array transducer with a conventional lens-focused transducer.
• To evaluate the transducer's efficacy in creating lesions in a tissue phantom and in vivo.

Main Methods:

• Fabrication of a 5 MHz annular array transducer using PZT-5H/epoxy composite with an integrated 30 MHz imaging probe.
• Testing of the array and a lens-focused transducer using a custom 16-channel high voltage pulse generator.
• Characterization of acoustic fields, transmit sensitivity, and cavitation voltage.
• In vitro and in vivo testing in a tissue phantom and a rat brain, respectively, with real-time ultrasound guidance.

Main Results:

• The annular array transducer exhibited a significantly increased depth-of-field compared to the lens-focused transducer, with comparable beamwidths.
• The array showed a lower cavitation voltage than the lens-focused transducer for similar operating depths.
• Successful creation of an elongated, homogenized lesion in a rat brain by electronically steering the focal length.
• Measured transmit sensitivity ranged from 0.113 to 0.167 MPa/V for the array and 0.192 MPa/V for the lens-focused transducer.

Conclusions:

• The developed image-guided annular array histotripsy transducer is effective for non-invasive tissue ablation.
• The transducer offers advantages in depth-of-field and electronic focal length steering over conventional methods.
• This technology holds promise for precise and controlled tissue homogenization in various medical applications.