A miniaturised focussed ultrasound transducer for soft tissue ablation

Stevenson, Jack Edward (2024) A miniaturised focussed ultrasound transducer for soft tissue ablation. PhD thesis, University of Glasgow.

Abstract

Focussed ultrasound surgery (FUS) in literature has been developed in the direction of large extra-corporeal transducers. With the rise of surgical robotics in recent years, a new niche is emerging in which miniaturised ultrasonic transducers for laparoscopic surgery will be required. Laparoscopic surgery can be advantageous to FUS transducer miniaturisation due to the robotic control being able to move the transducer into a position closer to the target tissue for treatment.

A new FUS transducer for soft tissue ablation is proposed, with a miniaturised configuration that can be readily integrated with a surgical robot. The FUS transducer consists of a single piezoceramic disc with a microballoon filled epoxy backing layer to approximate an air backing, and an acoustic Fresnel lens. The transducer was first developed as a virtual prototype in finite element analysis (FEA) that characterised the device’s acoustic field output with respect to different piezoelectric and acoustic lens materials.

The transducer housing and Fresnel lens were made from photopolymer resins in a mask stereolithography (mSLA) printer. Fifteen miniature FUS transducers were fabricated and tested, incorporating five different piezoceramic materials: a soft PZT, a specialised composition for high intensity focused ultrasound, a low acoustic impedance porous PZT, and a lead free piezoceramic. The devices were electrically matched to a high power amplifier and characterised at high power in an experimental high power impedance analysis.

A new technique was proposed to steer the focal region of the single element transducer by varying the driving signal frequency. This achieved a 64% positional change of the focus with a 1 MHz frequency change. Through finite element simulations and experimental characterisations of the acoustic field, it was shown that the porous piezoceramic, with lower piezoelectric and coupling coefficients, achieved the highest focal zone intensity and efficiency.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Supported by funding from the Engineering and Physical Sciences Research Council (EPSRC).
• Subjects: R Medicine > RD Surgery; T Technology > T Technology (General); T Technology > TK Electrical engineering. Electronics Nuclear engineering
• Colleges/Schools: College of Science and Engineering > School of Engineering
• Funder's Name: Engineering and Physical Sciences Research Council (EPSRC)
• Supervisor's Name: Lucas, Professor Margaret and Cochran, Professor Sandy
• Date of Award: 2024
• Depositing User: Theses Team
• Unique ID: glathesis:2024-84770
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 20 Dec 2024 12:04
• Last Modified: 20 Dec 2024 12:06
• Thesis DOI: 10.5525/gla.thesis.84770
• URI: https://theses.gla.ac.uk/id/eprint/84770

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