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University of Dundee DOCTOR of PHILOSOPHY the Cavitation

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University of Dundee DOCTOR of PHILOSOPHY the Cavitation University of Dundee DOCTOR OF PHILOSOPHY The cavitation subharmonic signal mechanistic source and optimised detection Johnston, Keith Award date: 2016 Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Download date: 30. Sep. 2021 The cavitation subharmonic signal: mechanistic source and optimised detection By Keith Johnston A thesis submitted in fulfilment of the requirements for the degree of doctor of Philosophy (PhD) to the School of Medicine, Nursing and Dentistry, University of Dundee, Scotland, UK. August 2016 Declaration I hereby declare that this thesis titled “The cavitation subharmonic signal: mechanistic source and optimised detection” has been prepared by me under the direct guidance of Dr Paul Prentice and Professor. Sandy Cochran as a part of my study for the award of PhD degree at the University of Dundee, Dundee, Scotland. I have not submitted this thesis previously for the award of any degree or diploma at any other institution. Signature: ..................................................................................... Date: 01/08/2016 Certificate This is to certify that Mr. Keith Johnston has done his research under my supervision and complied with all the requirements for the submission of this Doctor of Philosophy thesis to the University of Dundee, Dundee, Scotland. Signature: ..................................................................................... Date: 01/08/2016 i Acknowledgements Some three plus years ago, I was fortunate to gain a PhD studentship to study Cavitation. At that time my knowledge of bubbles was insignificant, but through the passion, expertise and dogmatism of my primary supervisor Paul, my knowledge and active enjoyment of studying bubbles has grown, for which I have to thank Paul. They are quite remarkable after all. My sincere thanks go to my second supervisors Professor Sandy Cochran for his mentoring and encouragement through tough times and Professor Cuschieri for his advice and financial support through CODiR European Research Council (ERC) funded grant. Additional thanks goes to Paul for financial support through TheraCav ERC grant. Anybody who has undertaken the monumental task of completing a PhD will know it cannot be completed without the help of friends, family and work colleges. Therefore, my gratitude is given to Björn and Spiros for helping me finding my feet at the beginning and teaching me about high-speed cameras and the ways of the lab. In addition, I would like to thank Rui, Xu, Han and Nhan for the early discussion of transducers and ultrasound. Special thanks go to the technicians Graham and Tim for sharing experience, knowledge of device design and general good banter and off course to Cecilia who, although very busy herself, has helped me a lot over the years. I am grateful to the guys from the CavLab, Kristoffer and Jae for their constructive feedback, help with MATLAB and the odd beer we enjoyed together. I would also like to thank Mariam for letting me use her chamber and help during writing up. To my ii good friends Markus, Stuart and Jan, thanks for the happy times spent over BBQ’s, which was a much needed requirement to relax from the lab and Helen and Brian, these guys have always been a constant source of joy, chat and were always there when I needed them. I think the love of and from a partner is the key to success, so I have to whole heartily thank my wife-to-be Julia, for giving me the strength to finish it. Your patience, love and the odd kick-in-the bum definitely got me to the finish line, for which I will be eternally grateful. Finally, I would like thank to my family for their love and support despite the distance. I would like to especially thank my mum, for her wise advice when nothing else helped and my brother Thomas for sending that application form in the first place; he is always a source of motivation. iii Dissemination of Thesis Publications Peer-reviewed journals • Keith Johnston, Cecilia Tapia-Siles, Bjoern Gerold, Michiel Postema, Sandy Cochran, Alfred Cuschieri, Paul Prentice. Periodic shock-emission from acoustically driven cavitation clouds: A source of the subharmonic signal. Ultrasonics, vol. 54, pp. 2151-2158, 2014. • Kristoffer Johansen, Jae Hee Song, Keith Johnston, Paul Prentice. Deconvolution of acoustically detected bubble-collapse shockwaves. Ultrasonics, 2016. (Currently under second stage of review process) • Keith Johnston, Jae Hee Song, Kristoffer Johansen, Paul. Prentice, Optimisation of a Single Element Passive Cavitation Detector for the Subharmonic Signal, Sensors 2016. (Under preparation) Conference papers • Keith Johnston, Sandy Cochran and Paul Prentice. Non-linear cavitation cloud oscillations in High Intensity Focused Ultrasound: A mechanistic source of the subharmonic signal. Ultrasonics Symposium (IUS), 2014, IEEE, 373-376. • Keith Johnston, Paul Prentice and Bjoern Gerold. Cavitation cloud translation in focused ultrasound. Ultrasonics Symposium (IUS), 2014 IEEE, 61-64. Conferences attended IEEE International Ultrasonic Symposium, Chicago Illinois USA, presentation entitled ‘Revealing the source of the Subharmonic signal’. 2014 iv Anglo-French Physical Acoustics Conference (AFPAC), Selsdon Park, Surrey UK, presentation entitled ‘Cavitation – cloud manipulation in dual frequency focused ultrasound’. 2014 National Physics Laboratory Cavitation Forum, Teddington London UK, poster presentation entitled ‘Cavitation – cloud manipulation in dual frequency focused ultrasound’. 2013 Awards • Keith Johnston, Sandy Cochran and Paul Prentice. Non-linear cavitation cloud oscillations in High Intensity Focused Ultrasound: A mechanistic source of the subharmonic signal. Ultrasonics Symposium (IUS), 2014, IEEE, 373-376. (IEEE IUS Student Paper Competition Award) Keith Johnston, Paul Prentice. Cavitation – cloud manipulation in dual frequency focused ultrasound. National Physics Laboratory Cavitation Forum 2013. (Best student poster prize) • Keith Johnston, Paul Prentice. Cavitation Detector Optimisation using PZFlex. PZFlex User Meeting 2015. (Best student poster prize) v Table of Content Declaration and certificate ......................................................................................i Acknowledgements ................................................................................................ ii Dissemination of thesis ........................................................................................... iv Glossary .................................................................................................................. x Acronyms .............................................................................................................. xi List of Figures .......................................................................................................xii List of Tables ......................................................................................................... xv Abstract ................................................................................................................ xvi 1 An introduction to acoustic cavitation, and the subharmonic signal .................... 1 2 Background ........................................................................................................ 7 2.1 Overview of ultrasound ............................................................................... 7 2.1.1 Sound as a wave ........................................................................... 7 2.1.2 A brief history of ultrasound for therapy ....................................... 9 2.1.3 Power and Intensity .................................................................... 14 2.1.4 Attenuation ................................................................................. 15 2.1.5 Radiation force ........................................................................... 16 2.1.6 Non-linear propagation ............................................................... 17 2.1.7 Microbubbles .............................................................................. 19 2.1.8 Various indices used for medical application .............................. 20 3 Cavitation ........................................................................................................ 23 3.1 A brief history of cavitation research ......................................................... 23 3.2 Acoustic cavitation .................................................................................... 26 3.2.1 Resonant frequency .................................................................... 28 3.2.2 Cavitation in a standing wave ..................................................... 30 3.2.3 The bjerknes forces ..................................................................... 31 3.2.4 Cavitation
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