scholarly journals Use of shock-wave exposures for accelerating thermal ablation of targeted tissue volumes

2019 ◽  
Author(s):  
Oleg Sapozhnikov ◽  
Wayne Kreider ◽  
Tatiana Khokhlova ◽  
Ari Partanen ◽  
Maria Karzova ◽  
...  
Keyword(s):  
Shock Wave ◽  
Thermal Ablation ◽  
Near Field ◽  
High Amplitude ◽  
Acoustic Propagation ◽  
Tissue Heating ◽  
Duty Cycles ◽  
Propagation Effects ◽  
Target Sites ◽  
Nonlinear Acoustic

In HIFU applications, nonlinear acoustic propagation effects can result in the formation of high-amplitude shocks at the focus, with amplitudes exceeding 100 MPa, leading to a significant increase in tissue heating at target sites. This effect has been used in a new pulsed-HIFU technology termed boiling histotripsy to mechanically liquefy tissue. In boiling histotripsy, such shock-wave millisecond-long pulses are delivered to the target sites at low duty cycles. Similar exposures, delivered at higher repetition rates may benefit thermal HIFU by shortening sonication and treatment times, reducing heating of near field and surrounding tissues, mitigating diffusion and perfusion effects, and providing sharper lesion margins. The goal of this project was to develop shock-enhanced thermal HIFU treatments and test their performance through a combination of simulations and experiments using a clinical Sonalleve V2 MR-HIFU system (Profound Medical Inc., Canada).

Implication of the distinctive bipolar intracardiac electrograms for ventricular arrhythmias arising from different regions of ventricular outflow tract

EP Europace ◽  
2020 ◽  
Vol 22 (9) ◽  
pp. 1367-1375
Author(s):  
Jia Li ◽  
Weiqian Lin ◽  
Cheng Zheng ◽  
Chi Zhang ◽  
Jiji Yu ◽  
...  
Keyword(s):  
Ventricular Arrhythmias ◽  
Ventricular Outflow Tract ◽  
High Amplitude ◽  
Outflow Tract ◽  
Correct Identification ◽  
Aortic Sinus ◽  
Distinctive Features ◽  
Long Duration ◽  
Target Sites ◽  
First Time

Abstract Aims To investigate the characteristics of bipolar intracardiac electrograms (bi-EGMs) in target sites of ventricular arrhythmias (VAs) originating from different regions of ventricular outflow tract (VOT). Methods and results Two hundred and seventy patients undergoing first-time ablation for VAs originated from distal great cardiac vein (DGCV), aortic sinus cusps (ASCs), or pulmonary sinus cusps (PSCs) were enrolled in present study. Local intracardiac bipolar recordings on 243 successful sites and 506 attempted but unsuccessful ablation sites were analysed. Specific potentials in bi-EGMs on successful sites were more common compared with unsuccessful sites (76.95%, 187/243 vs. 25.49%, 129/506, P < 0.05). A total of 60.00% (81/135) patients in ASCs group presented a presystolic short-duration fractionated potential, higher than 23.21% (13/56) in DGCV and 23.08% (12/52) in PSCs (all P < 0.05); 44.23% (23/52) patients in PSC group showed a presystolic high-amplitude discrete potential, while 1.79% (1/56) in DGCV and 2.22% (3/135) in ASCs (all P < 0.05); 41.07% (23/56) patients in DGCV group showed bi-EGMs of presystolic long-duration multicomponent fractionated potential, which was significantly higher than 3.85% (2/52) in PSCs and 4.44%(6/135) in ASCs (all P < 0.05). Conclusion Distinctive morphology of bi-EGMs during VAs can be found in different regions of VOT, which probably due to changes in the arrangements of myocardial sleeves. Correct identification and better understanding of the distinctive features of these bi-EGMs with regards to the anatomic location was important, the presence of specific potentials may add help in successful ablation.

scholarly journals A Lab-Scale Experiment Approach to the Measurement of Wall Pressure from Near-Field under Water Explosions by a Hopkinson Bar

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Xiongwei Cui ◽  
Xiongliang Yao ◽  
Yingyu Chen
Keyword(s):  
Shock Wave ◽  
Near Field ◽  
Underwater Explosion ◽  
Experimental System ◽  
Hopkinson Bar ◽  
Wall Pressure ◽  
Pressure Loading ◽  
Target Plate ◽  
Wave Pressure ◽  
Shock Wave Pressure

Direct measurement of the wall pressure loading subjected to the near-field underwater explosion is of great difficulty. In this article, an improved methodology and a lab-scale experimental system are proposed and manufactured to assess the wall pressure loading. In the methodology, a Hopkinson bar (HPB), used as the sensing element, is inserted through the hole drilled on the target plate and the bar’s end face lies flush with the loaded face of the target plate to detect and record the pressure loading. Furthermore, two improvements have been made on this methodology to measure the wall pressure loading from a near-field underwater explosion. The first one is some waterproof units added to make it suitable for the underwater environment. The second one is a hard rubber cylinder placed at the distal end, and a pair of ropes taped on the HPB is used to pull the HPB against the cylinder hard to ensure the HPB’s end face flushes with loaded face of the target plate during the bubble collapse. To validate the pressure measurement technique based on the HPB, an underwater explosion between two parallelly mounted circular target plates is used as the validating system. Based on the assumption that the shock wave pressure profiles at the two points on the two plates which are symmetrical to each other about the middle plane of symmetry are the same, it was found that the pressure obtained by the HPB was in excellent agreement with pressure transducer measurements, thus validating the proposed technique. To verify the capability of this improved methodology and experimental system, a series of minicharge underwater explosion experiments are conducted. From the recorded pressure-time profiles coupled with the underwater explosion evolution images captured by the HSV camera, the shock wave pressure loading and bubble-jet pressure loadings are captured in detail at 5  mm, 10  mm, …, 30  mm stand-off distances. Part of the pressure loading of the experiment at 35  mm stand-off distance is recorded, which is still of great help and significance for engineers. Especially, the peak pressure of the shock wave is captured.

scholarly journals The effect of electronically steering a phased array ultrasound transducer on near-field tissue heating

2011 ◽  
Vol 38 (9) ◽  
pp. 4971-4981 ◽  
Author(s):  
Allison Payne ◽  
Urvi Vyas ◽  
Nick Todd ◽  
Joshua de Bever ◽  
Douglas A. Christensen ◽  
...  
Keyword(s):  
Phased Array ◽  
Near Field ◽  
Ultrasound Transducer ◽  
Tissue Heating ◽  
Phased Array Ultrasound ◽  
Array Ultrasound

Influence of nozzle external geometry on wavepackets in under-expanded supersonic impinging jets

2021 ◽  
Vol 929 ◽  
Author(s):  
Shahram Karami ◽  
Julio Soria
Keyword(s):  
Shear Layer ◽  
Spectral Decomposition ◽  
Travelling Waves ◽  
Near Field ◽  
High Amplitude ◽  
Impinging Jets ◽  
The Other ◽  
Mode Shapes ◽  
Reflected Shock ◽  
Spatial Modes

In this study, large-eddy simulations are utilised to unravel the influence of the nozzle's external geometry on upstream-travelling waves in under-expanded supersonic impinging jets. Three configurations, a thin-lipped, a thin-lipped with a sponge and an infinite-lipped nozzle are considered with the other non-dimensionalised geometrical and flow variables identical for the three cases. Spectral proper orthogonal decomposition is applied to the Mack norm, i.e. the energy norm based on the stagnation energy, to obtain the spatial modes at their corresponding frequency. The spectral decomposition of the spatial modes at optimal and suboptimal frequencies is used to isolate the wavepackets into upstream- and downstream-propagating waves based on their phase velocity. It is found that the external geometry of the nozzle has a significant influence on the first-order statistics even though the governing non-dimensional parameters are the same for all three cases. Multiple peaks emerge in the energy spectra at distinct frequencies corresponding to axisymmetric azimuthal modes for each case. The downstream-propagating wavepackets have a high amplitude at the shear layer of the three jets with the mode shapes resembling Kelvin–Helmholtz instability waves, while the upstream-travelling wavepackets exist in the three regions of the near field, shear layer and inside of the jet. The barrel shock at the nozzle exit appears as a flexible shield, which prevents upstream-travelling waves from reaching the internal region of the nozzle, where the upstream-travelling waves travel obliquely with one side of the wavefront is crawling on the reflected shock while the other side is guided by the shear layer. These latter waves can reach the nozzle lip via inside of the jet. The spectral decomposition of the spatial modes at optimal and suboptimal frequencies show that all three forms of the near field, shear layer and inside jet upstream-travelling wavepackets contribute to the receptivity process while their contributions and strength are altered by the change of the external geometry of the nozzle.

scholarly journals The collapse of single bubbles and approximation of the far-field acoustic emissions for cavitation induced by shock wave lithotripsy

2011 ◽  
Vol 677 ◽  
pp. 305-341 ◽  
Author(s):  
A. R. JAMALUDDIN ◽  
G. J. BALL ◽  
C. K. TURANGAN ◽  
T. G. LEIGHTON
Keyword(s):  
Shock Wave ◽  
Shock Wave Lithotripsy ◽  
Near Field ◽  
Acoustic Emissions ◽  
Clinical Situation ◽  
Control Surface ◽  
Bubble Collapse ◽  
Far Field ◽  
Field Emissions ◽  
Computational Resources

Recent clinical trials have shown the efficacy of a passive acoustic device used during shock wave lithotripsy (SWL) treatment. The device uses the far-field acoustic emissions resulting from the interaction of the therapeutic shock waves with the tissue and kidney stone to diagnose the effectiveness of each shock in contributing to stone fragmentation. This paper details simulations that supported the development of that device by extending computational fluid dynamics (CFD) simulations of the flow and near-field pressures associated with shock-induced bubble collapse to allow estimation of those far-field acoustic emissions. This is a required stage in the development of the device, because current computational resources are not sufficient to simulate the far-field emissions to ranges of O(10 cm) using CFD. Similarly, they are insufficient to cover the duration of the entire cavitation event, and here simulate only the first part of the interaction of the bubble with the lithotripter shock wave in order to demonstrate the methods by which the far-field acoustic emissions resulting from the interaction can be estimated. A free-Lagrange method (FLM) is used to simulate the collapse of initially stable air bubbles in water as a result of their interaction with a planar lithotripter shock. To estimate the far-field acoustic emissions from the interaction, this paper developed two numerical codes using the Kirchhoff and Ffowcs William–Hawkings (FW-H) formulations. When coupled to the FLM code, they can be used to estimate the far-field acoustic emissions of cavitation events. The limitation of the technique is that it assumes that no significant nonlinear acoustic propagation occurs outside the control surface. Methods are outlined for ameliorating this problem if, as here, computational resources cannot compute the flow field to sufficient distance, although for the clinical situation discussed, this limitation is tempered by the effect of tissue absorption, which here is incorporated through the standard derating procedure. This approach allowed identification of the sources of, and explanation of trends seen in, the characteristics of the far-field emissions observed in clinic, to an extent that was sufficient for the development of this clinical device.

scholarly journals Experimental observations of diurnal acoustic propagation effects in seagrass meadows on the Dongsha Atoll

2019 ◽  
Vol 146 (3) ◽  
pp. EL279-EL285 ◽  
Author(s):  
Andrea Y. Y. Chang ◽  
Linus Y. S. Chiu ◽  
Michael H.-K. Mok ◽  
Keryea Soong ◽  
Wei-Jhe Huang
Keyword(s):  
Acoustic Propagation ◽  
Seagrass Meadows ◽  
Propagation Effects ◽  
Dongsha Atoll

Source and Propagation Effects on Near-Field Co-Eruptive Ground Motion at Santiaguito Volcano, Guatemala

2012 ◽  
Vol 102 (2) ◽  
pp. 696-706 ◽  
Author(s):  
J. F. Anderson ◽  
J. M. Lees ◽  
G. P. Waite ◽  
J. B. Johnson
Keyword(s):  
Ground Motion ◽  
Near Field ◽  
Propagation Effects

MULTIPLICATIVE PADÉ PE FORMULATION APPLIED TO SWAM'99 TEST CASES

2001 ◽  
Vol 09 (01) ◽  
pp. 227-241 ◽  
Author(s):  
WOOJAE SEONG ◽  
BYUNGHO CHOI
Keyword(s):  
Parabolic Equation ◽  
Shallow Water ◽  
Environmental Changes ◽  
Near Field ◽  
Acoustic Propagation ◽  
Acoustic Modeling ◽  
Test Cases ◽  
Underwater Sound ◽  
Depth Direction ◽  
National University

Accurate forward modeling of acoustic propagation is crucial in underwater sound applications that rely on coherent field predictions, such as source localization and geoacoustic inversion based on matched field processing concepts. As acoustic propagation in shallow water environments becomes important in recent years, range-dependent modeling due to environmental changes has to be considered of which parabolic equation (PE) method has received widespread use because they are accurate and relatively fast. In this paper, Seoul National University parabolic equation (SNUPE) employing a multiplicative Padé formulation is developed. Linearization of the depth direction operator is achieved via expansion into a multiplication form of Padé approximation. To approximate the depth directional equation, Galerkin's method is used with partial collocation to achieve computational efficiency. To approximate the range directional equation, Crank–Nicolson's method is used. Finally, numerical self-starter has been used to initiate the near-field solution. The Shallow Water Acoustic Modeling (SWAM'99) Workshop provides an opportunity to test SNUPE's accuracy and compare its results with others for a variety of synthetic environments. In this paper, the numerical implementation and accuracy of SNUPE is tested by comparing with RAM12 results for the SWAM'99 test cases. Numerical experiments for SWAM'99 test cases give satisfactory results in accuracy for SNUPE and show the importance of the bottom information in the shallow water acoustic modeling.

scholarly journals The Fluid-Solid Interaction Dynamics between Underwater Explosion Bubble and Corrugated Sandwich Plate

2016 ◽  
Vol 2016 ◽  
pp. 1-21
Author(s):  
Hao Wang ◽  
Yuan Sheng Cheng ◽  
Jun Liu ◽  
Lin Gan
Keyword(s):  
Shock Wave ◽  
Failure Modes ◽  
Sandwich Structures ◽  
Numerical Models ◽  
Near Field ◽  
Three Dimensional ◽  
Underwater Explosion ◽  
Bubble Collapse ◽  
Fe Model ◽  
Wave Load

Lightweight sandwich structures with highly porous 2D cores or 3D (three-dimensional) periodic cores can effectively withstand underwater explosion load. In most of the previous studies of sandwich structure antiblast dynamics, the underwater explosion (UNDEX) bubble phase was neglected. As the UNDEX bubble load is one of the severest damage sources that may lead to structure large plastic deformation and crevasses failure, the failure mechanisms of sandwich structures might not be accurate if only shock wave is considered. In this paper, detailed 3D finite element (FE) numerical models of UNDEX bubble-LCSP (lightweight corrugated sandwich plates) interaction are developed by using MSC.Dytran. Upon the validated FE model, the bubble shape, impact pressure, and fluid field velocities for different stand-off distances are studied. Based on numerical results, the failure modes of LCSP and the whole damage process are obtained. It is demonstrated that the UNDEX bubble collapse jet local load plays a more significant role than the UNDEX shock wave load especially in near-field underwater explosion.

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