Development of Histotripsy Focused Ultrasound Devices Using Rapid Prototyping Methods

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.