Acoustic sensing of renal stone fragmentation in extracorporeal shockwave lithotripsy

Abstract

This thesis describes the research carried out by the author on the exploitation of acoustic emissions detected during extracorporeal shockwave lithotripsy (a non-invasive procedure for the treatment of urinary stones) to develop a new diagnostic system. The work formed part of a research project on lithotripsy undertaken by the University of Southampton in collaboration with Guy's and St Thomas' NHS Foundation Trust (London) and a UK based company, Precision Acoustics Ltd (Dorchester). It takes to a clinical conclusion the proposition made by Leighton and Coleman in 1992 that it might be possible to build a sensor which would automatically exploit these passive acoustic emissions to monitor the efficacy of a lithotripsy treatment. The work, predominantly experimental, involved both in vitro and in vivo investigations. In particular, a first prototype diagnostic system (i.e. sensor plus analysis software) was developed and tested in vitro during trials which included the use of a novel cavitation sensor (on loan from the National Physical Laboratory, Teddington) and stone phantoms designed by the author. This initial system was, then, refined and tested during clinical trials that involved 130 patients. A preliminary trial on 51 patients aimed at refining the system and gathering knowledge on the features of emissions recorded in vivo to produce an on-line monitoring system. This trial was followed by other two trials that compared the output of the on-line acoustic system against the ‘gold standard’ X-Ray assessment of treatments outcomes. The former of these two trials involved 30 patients, and empirically defined the values of the key parameters (identified during the in vitro tests) that would be used as the basis of the diagnosis. In particular, a classification rule of treatments as being successful or unsuccessful was identified, and shown to agree significantly (kappa=0.95) with the ‘gold standard’ follow-up assessment. The latter trial tested the final system on 49 patients and confirmed an accurate treatment classification (kappa=0.94) in terms of the successful/unsuccessful criterion.

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Identifiers

ORCID for T.G. Leighton: orcid.org/0000-0002-1649-8750

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