Author: Darcy Dunn-Lawless
Dunn-Lawless, Darcy, 2021 An implantable ultrasound transmission circuit for monitoring cancer and enhancing bone growth, Flinders University, College of Science and Engineering
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This thesis describes a new application of medical ultrasound technology: an implant capable of producing ultrasound waves such that images may be captured and therapy applied from within the body. Specifically, the subject of this work is a new device intended for cancer patients who have undergone orthopaedic surgery, which is capable of both recording images to monitor for tumour recurrence, and applying ultrasound therapy to enhance the healing of the damaged bones. This medical device concept was developed through a systematic review of the literature and an interview process conducted with seven clinicians and three lay volunteers. The literature review was performed in accordance with PRISMA guidelines with the intent to discover what new clinical applications have been proposed for implantable ultrasound, and where there are gaps in the current research. The discussions with clinicians helped to refine the device concept, and produced a list of design requirements for the system that were graded for their importance. Design specifications were then generated and researched to find target values that the design should aim to meet, and thresholds for acceptable performance. The Quality Function Deployment method was used to identify dependencies between these specifications, and assess their relative importance to the device based on their relationships with the design requirements that the users valued most. One component of this new implant, the ultrasound transmission circuitry, was then practically designed and tested. The most suitable concept for realising this transmitter was found to be a custom-designed Application Specific Integrated Circuit. This circuit was designed using the Verilog hardware description language and prototyped on a Field Programmable Gate Array, with a custom Printed Circuit Board created to handle the high voltage transmission signals. Components of the prototype were electrically tested using a simulator and logic analyser, then an oscilloscope was used to test the system as a whole. Finally, the prototype was acoustically tested by placing its transducer in a water bath and measuring a proxy for the sound pressure in different areas of the output ultrasound field. These tests indicated that the device was capable of producing focussed ultrasound as intended. This project has therefore resulted in the creation of a new medical implant concept and the successful design and construction of its first component.
Keywords: Ultrasound, Implant, Implantable Ultrasound, Cancer Monitoring, Diagnostic Ultrasound, Therapeutic Ultrasound, Bone Growth, ASIC, Application-Specific Integrated Circuit, IC, Integrated Circuit, CMUT, Capacitive Micromachined Ultrasound Transducer
Subject: Engineering thesis
Thesis type: Masters
Completed: 2021
School: College of Science and Engineering
Supervisor: Professor Karen Reynolds