Control of the dynamics of a boiling vapour bubble using pressure-modulated high intensity focused ultrasound without the shock scattering effect: A first proof-of-concept study

• DOI: 10.1016/j.ultsonch.2021.105699
• Publication Date: 2021-07-31T15:25:36Z
• Authors: Ki Joo Pahk
• Keywords: High-intensity focused ultrasound

Boiling histotripsy is a promising High-Intensity Focused Ultrasound (HIFU) technique that can be used to induce mechanical tissue fractionation at the HIFU focus via cavitation. Two different types of cavitation produced during boiling exposure contribute towards destruction: (1) vapour bubble and (2) clouds in between source. Control extent degree damage by necessary when treating solid tumour adjacent normal or major blood vessels. This is, however, difficult achieve with due stochastic formation shock scattering-induced inertial clouds. In present study, new method termed pressure-modulated shockwave proposed as an alternative addition without inducing scattering effect. The concept (a) generate localised heating (b) subsequently control its lifetime through manipulating peak pressure magnitudes pulse length. To demonstrate feasibility method, dynamics induced optically transparent liver phantom were investigated using high speed camera passive detection systems under single 10, 50 100 ms-long 2, 3.5 5 MHz varying positive negative amplitudes from 89 MPa −3.7 −14.6 focus. Furthermore, numerical simulation 2D nonlinear wave propagation presence field was conducted numerically solving generalised Westervelt equation. experimental results showed that, histotripsy, bubbles generated merged together, forming larger (of order few hundred micron) coalesced then persisted maintained within focal zone until end (10, 50, ms). most importantly, no violent which typically appear occurred excitation (i.e. effect). likely because magnitude backscattered acoustic below cloud intrinsic threshold. size gradually increased magnitudes. addition, oval shaped lesion length 0.6 mm width 0.1 appeared phantom, whereas form tadpole (length: 2.7 mm, width: 0.3 mm) histotripsy. Taken these suggest could potentially more spatially destruction desired controlling