Pahk, Ki Joo Gelat, Pierre Kim, Hyungmin Saffari, Nader 2024-01-19T21:30:15Z 2024-01-19T21:30:15Z 2021-09-04 2018-12 0301-5629 https://pubs.kist.re.kr/handle/201004/120645 Boiling histotripsy is a non-invasive, cavitation-based ultrasonic technique which uses a number of millisecond pulses to mechanically fractionate tissue. Though a number of studies have demonstrated the efficacy of boiling histotripsy for fractionation of solid tumours, treatment monitoring by cavitation measurement is not well studied because of the limited understanding of the dynamics of bubbles induced by boiling histotripsy. The main objectives of this work are to (a) extract qualitative and quantitative features of bubbles excited by shockwaves and (b) distinguish between the different types of cavitation activity for either a thermally or a mechanically induced lesion in the liver. A numerical bubble model based on the Gilmore equation accounting for heat and mass transfer (gas and water vapour) was developed to investigate the dynamics of a single bubble in tissue exposed to different High Intensity Focused Ultrasound fields as a function of temperature variation in the fluid. Furthermore, ex vivo liver experiments were performed with a passive cavitation detection system to obtain acoustic emissions. The numerical simulations showed that the asymmetry in a shockwave and water vapour transport are the key parameters which lead the bubble to undergo rectified growth at a boiling temperature of 100 degrees C. The onset of rectified radial bubble motion manifested itself as (a) an increase in the radiated pressure and (b) the sudden appearance of higher order multiple harmonics in the corresponding spectrogram. Examining the frequency spectra produced by the thermal ablation and the boiling histotripsy exposures, it was observed that higher order multiple harmonics as well as higher levels of broadband emissions occurred during the boiling histotripsy insonation. These unique features in the emitted acoustic signals were consistent with the experimental measurements. These features can, therefore, be used to monitor (a) the different types of acoustic cavitation activity for either a thermal ablation or a mechanical fractionation process and (b) the onset of the formation of a boiling bubble at the focus in the course of HIFU exposure. (E-mail: n.saffari@ucl.ac.uk) (C) 2018 World Federation for Ultrasound in Medicine & Biology. All rights reserved. English ELSEVIER SCIENCE INC INTENSITY FOCUSED ULTRASOUND THERMODYNAMIC PROPERTIES ACOUSTIC PRESSURE LESION FORMATION IN-VITRO CAVITATION TISSUE VAPOR WATER MECHANISMS BUBBLE DYNAMICS IN BOILING HISTOTRIPSY Article 10.1016/j.ultrasmedbio.2018.07.025 1 ULTRASOUND IN MEDICINE AND BIOLOGY, v.44, no.12, pp.2673 - 2696 ULTRASOUND IN MEDICINE AND BIOLOGY 44 12 2673 2696 scie scopus 000448664300024 2-s2.0-85053345819 Acoustics Radiology, Nuclear Medicine & Medical Imaging Acoustics Radiology, Nuclear Medicine & Medical Imaging Article INTENSITY FOCUSED ULTRASOUND THERMODYNAMIC PROPERTIES ACOUSTIC PRESSURE LESION FORMATION IN-VITRO CAVITATION TISSUE VAPOR WATER MECHANISMS high intensity focused ultrasound boiling histotripsy cavitation monitoring