Histotripsy is a nonthermal ultrasound therapy used to treat cancer noninvasively by tissue mechanical fractionation with cavitation bubble clouds. Histotripsy is conducted through focused ultrasound transducers, where the piezoceramic (PZT) plate or disc, which emits the ultrasound wave, is the fundamental unit of the transducer. For modular prototype histotripsy designs, these PZTs are housed in a 3D printed focused lens. However, 3D printing transducer components can be time consuming and expensive when scaling up manufacturing, and 3D printing is limited in material selection for transducer applications. This thesis investigates the use of a novel fabrication process for prototype focused ultrasound transducers, injection molding, with an in-house benchtop injection molding machine. Acoustic material properties for investigated injection molded materials, ABS, GPPS, 30% glass filled nylon, nylon 6/6, and nylon 101, are quantified experimentally. Single elements are constructed with injection molded lenses made from ABS, 30% glass-filled nylon, nylon 6/6, and nylon 101 on an in-house benchtop machine. Results show that injection molding is a novel feasible method for applications in focused ultrasound devices and the investigated plastics have favorable properties for developing prototype histotripsy transducers, comparable to 3D printed transducer housings. Future work aims to apply injection molding to various transducer designs and additional materials for focused ultrasound therapy devices. / Master of Science / Histotripsy is a cancer therapy that can noninvasively treat tumors without surgery. This is done through devices called focused ultrasound transducers which emit ultrasound waves to administer treatment to ablate tumors. These transducers are constructed using 3D printing methods, but this can be limiting when scaling up manufacturing or in material selection for transducer applications, therefore additional fabrication methods are needed. This thesis presents injection molding as a novel method for making transducer components with an in-house benchtop injection molding machine. Five plastic materials are investigated to determine ultrasound properties that would identify preferred transducer materials. Single element transducers are made from injection molded materials, tested, and compared with 3D printed single element transducers. Results of this thesis show that injection molding is a feasible manufacturing method capable of producing transducers for histotripsy, and researched materials have favorable properties for this application. In future research, additional injection molded materials should be investigated and multiple transducer designs created for injection molding fabrication. These injection molded transducers can be applied to histotripsy or applied to other focused ultrasound therapies.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/110395 |
| Date | 01 June 2022 |
| Creators | Sheppard, Hannah Olivia |
| Contributors | Department of Biomedical Engineering and Mechanics, Vlaisavljevich, Eli, Muelenaer, Andre Albert, Arena, Christopher Brian |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf, application/pdf |
| Rights | Creative Commons Attribution 4.0 International, http://creativecommons.org/licenses/by/4.0/ |
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