Reduction of Bubble Cavitation by Modifying the Diffraction Wave from a Lithotripter Aperture

Abstract

Purpose: A new method was devised to suppress the bubble cavitation in the lithotripter focal zone to reduce the propensity of shockwave-induced renal injury. Materials and Methods: An edge extender was designed and fabricated to fit on the outside of the ellipsoidal reflector of an electrohydraulic lithotripter to disturb the generation of diffraction wave at the aperture, but with little effect on the acoustic field inside the reflector. Results: Although the peak negative pressures at the lithotripter focus using the edge extender at 20 kV were similar to that of the original configuration (-11.1 -0.9 vs -10.6 -0.7 MPa), the duration of the tensile wave was shortened significantly (3.2 -0.54 vs 5.83 -0.56 ls, P < 0.01). There is no difference, however, in both the amplitude and duration of the compressive shockwaves between these two configurations as well as the -6 dB beam width in the focal plane. The significant suppression effect of bubble cavitation was confirmed by the measured bubble collapse time using passive cavitation detection. At the lithotripter focus, while only about 30 shocks were needed to rupture a blood vessel phantom using the original HM-3 reflector at 20 kV, no damage could be produced after 300 shocks using the edge extender. Meanwhile, the original HM-3 lithotripter at 20 kV can achieve a stone comminution efficiency of 50.4 -2.0% on plaster-of-Paris stone phantom after 200 shocks, which is comparable to that of using the edge extender (46.8 -4.1%, P = 0.005). Conclusions: Modifying the diffraction wave at the lithotripter aperture can suppress the shockwave-induced bubble cavitation with significant reduced damage potential on the vessel phantom but satisfactory stone comminution ability.

An analysis of the acoustic cavitation noise spectrum: The role of periodic shock waves

“…It is known that the shock wave emitted by a collapsing bubble is quite distinct from other underwater shock waves, such as generated for lithotripsy, 14 or when a laser pulse is focused into a liquid, to generate a laser-induced bubble 15 [see Fig. 12(a) in the Appendix].…”

Intraluminal bubble dynamics induced by lithotripsy shock wave

“…Another strategy for minimizing vascular injury is to reduce the intraluminal bubble expansion by modifying the profile, sequence, and spatial distribution of LSW, such as with in situ pulse superposition to the LSW tensile wave [37,38], inver sion of LSW using a pressure release reflector [39][40][41], use of an acoustic diode to reduce the amplitude of the tensile wave [42], and modifying the diffraction wave from the lithotripter aperture by an edge blocker and consequently decreasing its contribution to the LSW tensile wave at the focal region [43]. Since the maximum bubble size in a free field is proportional to bubble collapse time, the reduction of bubble cavitation was usually verified by PCD.…”

Sonoporation-induced cell membrane permeabilization and cytoskeleton disassembly at varied acoustic and microbubble-cell parameters

“…For instance, it has been demonstrated that the sonoporation pore size is highly correlated with acoustic driving parameters, e.g ., acoustic pressure, sonication duration time and pulse repetition frequency 11 , 24 – 26 . Heterogeneous cellular membrane permeability variations have also been observed at different microbubble-cell distance 27 , 28 , bubble size 23 and microbubble-cell numbers 29 , 30 . However, these studies mainly explored the membrane-level responses to microbubble-mediated sonoporation and did not fully illuminate the impacts of acoustic driving parameters and microbubble-to-cell relative parameters on deeper cellular structures, such as the cytoskeleton.…”