Ultrasound Frequency Research Articles

A-352 - The use of High Frequency Ultrasound in Cutaneous Oncology Surgery

A-352 - The use of High Frequency Ultrasound in Cutaneous Oncology Surgery

Clinical Study and Progress of High Frequency Ultrasound in Peripheral Neuropathy

Clinical Study and Progress of High Frequency Ultrasound in Peripheral Neuropathy

Formation Model for Acoustic Characteristics of Solid Media with Ordered Fracturing

Introduction. The development of new structural materials and improvement of existing technologies for the production of new products on their basis lead to the emergence of new types of medium discontinuities. Therefore, the development of new models of discontinuities that take the previously ignored parameters into account seems to be relevant for the purposes of nondestructive testing and structural measurements. This concerns, e.g., the roughness of adjacent surfaces of microcrack ordered sets.Aim. Theoretical substantiation for the processes of elastic waves propagation through an elastic medium containing an ordered lattice of microcracks with boundary conditions in the linear slip approximation, modified by taking into account the parameters of micro-convexities of microcrack rough boundaries. Database formation for experimental studies aimed at determining the physical and mechanical characteristics of structural materials.Materials and methods. The acoustic characteristics of materials were determined based on the derivation and solutions of dispersion equations describing the formation and propagation of effective longitudinal, transverse, and Rayleigh surface elastic waves in elastic media with ordered cracking. Their values were also used to determine the effective speed of Rayleigh surface waves.Results. The conducted simulation of elastic wave formation processes showed that an increase in the concentration of microcracks leads to a decrease in the phase velocities of effective longitudinal, transverse, and surface waves, as well as to an increase in the attenuation coefficients at given ultrasound frequencies and material parameters.Conclusion. The radius of the microsphere that replaces the surface micro-convexity and the roughness parameter Rz have a significant impact on the formation of physical and mechanical characteristics of materials, which are determined by the results of ultrasonic measurements. The developed model can be recommended as a basis for interpreting the results of ultrasonic measurements.

Трещинообразование натуральной и модифицированной прессованием древесины березы повислой (Betula pendula Roth): эффект показателя внутреннего трения под влиянием внешних возмущений

Obtaining information about the presence of cracks in raw materials, blanks and wood products is neces-sary to make a decision on the purposes of its subsequent processing and operation. The method for diagnosing cracks in wood is based on measuring internal friction. For prepared samples of natural and modified wood, sawn from the stem part of drooping birch (Betula pendula Roth) trees growing in Khlevensky Forestry, Lipetsk region. (52.184130, 39.110463, ASL 157m), exposed to radial and tangential directions with ultrasound (frequency 24.5 kHz, exposure 0-20 minutes, step 5 minutes) and pulsed magnetic field (strength - 0.3 T, exposure 0-2 minutes, step 0.5 minutes). Next, the internal friction of the samples was studied on an experimental setup by measuring the logarithmic damping decrement based on free-bending vibrations. The absolute values of the dimensionless coefficient of internal friction Q-1, as the main structural parameter for samples of natural and modified wood, were obtained at a significance level of p=0.95: for humidity, in the presence of one crack, Q-1 decreased by 7.04% (D=0.08), in the presence of two cracks - by 8.4% (D=0.15), in the presence of three cracks - by 9.06% (D=0.15); for ultrasound in the presence of one crack Q-1 decreased by 7.17% (D=0.05), in the presence of two cracks - by 8.46% (D=0.05), in the presence of three cracks - by 9.12% (D=0.09); for a pulsed magnetic field in the presence of one crack Q-1 decreased by 7.14% (D=0.05), in the presence of two cracks - by 8.39% (D=0.09), in the presence of three cracks - by 9.02% (D=0.09). When testing the samples of natural wood and pressure-modified drooping birch (Betula pendula Roth) wood, we obtained an asymptotic equation was obtained for ap-proximating the dependence of the decrease in Q-1 on the number of cracks, with the approximation value R2=0.994. The study of the dependence of internal friction on the process of crack formation in various types of wood provides preparation for the next stage - the construction of a prototype system for non-destructive testing of defects.

Influence of ultrasound transmit frequency on measurement of global longitudinal strain on 2D speckle tracking echocardiography

The reproducibility of longitudinal strain measured by 2D speckle tracking echocardiography (2DSTE) may be affected by ultrasound settings. This study investigated the effect of transmit ultrasound frequency on global longitudinal strain (GLS) by 2DSTE. Apical, 2- and 4-chamber, and long-axis views were obtained in consecutive 162 patients using Philips ultrasound devices. Three different frequency presets were used sequentially: high resolution (HRES, 1.9 to 2.1 MHz), general (HGEN, 1.6 to 1.8 MHz), and penetration mode (HPEN, 1.3 to 1.6 MHz). GLS values were determined for each preset using the Philips Q-station software, resulting in GLS-HRES, GLS-HGEN, and GLS-HPEN. Among the 151 patients with successfully measured GLS, a significant difference in GLS was observed among the three presets (p < 0.0001). GLS-HRES (− 17.9 ± 4.4%) showed a slightly smaller magnitude compared to GLS-HGEN (− 18.8 ± 4.5%, p < 0.0001) and GLS-HPEN (− 18.8 ± 4.5%, p < 0.0001), with absolute differences of 1.1 ± 1.0% and 1.1 ± 1.2%, respectively. This variation in GLS with frequency was evident in patients with both optimal (n = 104) and suboptimal (n = 47) image quality and remained consistent regardless of ultrasound devices, ischemic etiology, or ejection fraction. In conclusion, ultrasound frequency had only a modest effect on GLS measurements. GLS may be reliably assessed in most cases regardless of the ultrasound frequency used.

Seismic wave dispersion and attenuation resulting from multiscale wave-induced fluid flow in partially saturated porous media

SUMMARY Sedimentary rocks are typical heterogeneous porous media induced by fluid patches and pore fabric. It is well acknowledged that the wave-induced fluid flow (WIFF) at different scales will cause seismic wave dispersion and attenuation in a wide frequency range. Consequently, modelling wave dispersion and attenuation due to multiscale WIFF is of significance for reservoir characterization from multiscale geophysical measurement and interpretation. In this study, the multiscale WIFF in partially saturated porous media, including global, 3-D mesoscopic and squirt flows, are investigated. And we derive the wave equations by introducing the Rayleigh's spherical bubble oscillation and the porous grain models into Santos poroelasticity theory. Numerical simulations demonstrate that the multiscale model can interpret the transition of rock states as frequency increases and capture the broad-band seismic wave dispersion and attenuation characteristics, which are directly associated with the heterogeneity scale. Besides, the multiscale model can be degraded to a single- or dual-scale model under specific parameters. We validate the proposed model with board-band experimental data of partially saturated sandstones, confirming its comprehensive characterization of velocity dispersion and attenuation over a wider range of frequencies. Moreover, the model successfully interprets the unrelaxed state of partially saturated rock at ultrasound frequencies.

Dispersion Engineering by Hybridizing the Back-Folded Soft Mode of Monomode Elastic Metamaterials with Stiff Acoustic Modes.

In many cases, the hybridization of two or more excitation modes in solids has led to new and useful dispersion relations of waves. Well-studied examples are phonon polaritons, plasmon polaritons, particle-plasmon polaritons, cavity polaritons, and magnetic resonances at optical frequencies. In all of these cases, the lowest propagating mode couples to a finite-frequency localized resonance. Herein, the unusual metamaterial phonon dispersion relations arising from the hybridization of an ordinary acoustical phonon mode with a back-folded soft or easy phonon mode of a monomode elastic metamaterial are discussed. Conceptually, the single easy mode can have strictly zero wave velocity. In reality, its wave velocity is very much smaller than that of all other modes. Considering polymeric three-dimensional printed elastic monomode metamaterials at ultrasound frequencies, it is shown theoretically and experimentally that the resulting pronounced avoided crossing, with a frequency splitting comparable to the mid-frequency, leads to backward-wave behavior for the lowest band over a broad frequency range, conceptually at zero loss.

Optimizing irradiation conditions for low-intensity pulsed ultrasound to upregulate endothelial nitric oxide synthase.

Here we aimed to develop a minimally invasive treatment for ischemic heart disease and demonstrate that low-intensity pulsed ultrasound (LIPUS) therapy improves myocardial ischemia by promoting myocardial angiogenesis in a porcine model of chronic myocardial ischemia. Studies to date determined the optimal treatment conditions within the range of settings available with existing ultrasound equipment and did not investigate a wider range of conditions. We investigated a broad range of five parameters associated with ultrasound irradiation conditions that promote expression of endothelial nitric oxide synthase (eNOS), a key molecule that promotes angiogenesis in human coronary artery endothelial cells (HCAEC). Suboptimal irradiation conditions included 1-MHz ultrasound frequency, 500-kPa sound pressure, 20-min total irradiation time, 32-48-[Formula: see text] pulse duration, and 320-[Formula: see text] pulse repetition time. Furthermore, a proposed index, [Formula: see text], calculated as the product of power and the total number of irradiation cycles applied to cells using LIPUS, uniformly revealed the experimental eNOS expression associated with the various values of five parameters under different irradiation conditions. We determined the suboptimal ultrasound irradiation conditions for promoting eNOS expression in HCAEC.

Rapid intraoperative multi-molecular diagnosis of glioma with ultrasound radio frequency signals and deep learning

Molecular diagnosis is crucial for biomarker-assisted glioma resection and management. However, some limitations of current molecular diagnostic techniques prevent their widespread use intraoperatively. With the unique advantages of ultrasound, this study developed a rapid intraoperative molecular diagnostic method based on ultrasound radio-frequency signals. We built a brain tumor ultrasound bank with 169 cases enrolled since July 2020, of which 43483 RF signal patches from 67 cases with a pathological diagnosis of glioma were a retrospective cohort for model training and validation. IDH1 and TERT promoter (TERTp) mutations and 1p/19q co-deletion were detected by next-generation sequencing. We designed a spatial-temporal integration model (STIM) to diagnose the three molecular biomarkers, thus establishing a rapid intraoperative molecular diagnostic system for glioma, and further analysed its consistency with the fifth edition of the WHO Classification of Tumors of the Central Nervous System (WHO CNS5). We tested STIM in 16-case prospective cohorts, which contained a total of 10384 RF signal patches. Two other RF-based classical models were used for comparison. Further, we included 20 cases additional prospective data for robustness test (ClinicalTrials.govNCT05656053). In the retrospective cohort, STIM achieved a mean accuracy and AUC of 0.9190 and 0.9650 (95% CI, 0.94-0.99) respectively for the three molecular biomarkers, with a total time of 3s and a 96% match to WHO CNS5. In the prospective cohort, the diagnostic accuracy of STIM is 0.85±0.04 (mean±SD) for IDH1, 0.84±0.05 for TERTp, and 0.88±0.04 for 1p/19q. The AUC is 0.89±0.02 (95% CI, 0.84-0.94) for IDH1, 0.80±0.04 (95% CI, 0.71-0.89) for TERTp, and 0.85±0.06 (95% CI, 0.73-0.98) for 1p/19q. Compared to the second best available method based on RF signal, the diagnostic accuracy of STIM is improved by 16.70% and the AUC is improved by 19.23% on average. STIM is a rapid, cost-effective, and easy-to-manipulate AI method to perform real-time intraoperative molecular diagnosis. In the future, it may help neurosurgeons designate personalized surgical plans and predict survival outcomes. A full list of funding bodies that contributed to this study can be found in the Acknowledgements section.

Hermite-scan imaging for differentiating glioblastoma from normal brain: Simulations and ex vivo studies for applications in intra-operative tumor identificationa).

Hermite-scan (H-scan) imaging is a tissue characterization technique based on the analysis of raw ultrasound radio frequency (RF) echoes. It matches the RF echoes to Gaussian-weighted Hermite polynomials of various orders to extract information related to scatterer diameter. It provides a color map of large and small scatterers in the red and blue H-scan image channels, respectively. H-scan has been previously reported for characterizing breast, pancreatic, and thyroid tumors. The present work evaluated H-scan imaging to differentiate glioblastoma tumors from normal brain tissue ex vivo. First, we conducted 2-D numerical simulations using the k-wave toolbox to assess the performance of parameters derived from H-scan images of acoustic scatterers (15-150 μm diameters) and concentrations (0.2%-1% w/v). We found that the parameter intensity-weighted percentage of red (IWPR) was sensitive to changes in scatterer diameters independent of concentration. Next, we assessed the feasibility of using the IWPR parameter for differentiating glioblastoma and normal brain tissues (n = 11 samples per group). The IWPR parameter estimates for normal tissue (44.1% ± 1.4%) were significantly different (p < 0.0001) from those for glioblastoma (36.2% ± 0.65%). These findings advance the development of H-scan imaging for potential use in differentiating glioblastoma tumors from normal brain tissue during resection surgery.

A note on the audio sound power generated by a parametric array loudspeaker.

Understanding the sound power characteristics of parametric array loudspeakers (PALs) poses a unique challenge due to the nonlinear process involved. This work addresses this issue by employing the spherical convolution directivity model to obtain the far field intensity, which is then used to calculate the sound power radiated by a PAL. The results reveal that the audio sound power is approximately proportional to the square of the audio frequency and the aperture size, while inversely proportional to the ultrasound frequency. Additionally, the conversion efficiency from ultrasound to audio sound is found to be generally below 0.15% for typical configurations.

Development and optimisation of in vitro sonodynamic therapy for glioblastoma

Sonodynamic therapy (SDT) is currently on critical path for glioblastoma therapeutics. SDT is a non-invasive approach utilising focused ultrasound to activate photosensitisers like 5-ALA to impede tumour growth. Unfortunately, the molecular mechanisms underlying the therapeutic functions of SDT remain enigmatic. This is primarily due to the lack of intricately optimised instrumentation capable of modulating SDT delivery to glioma cells in vitro. Consequently, very little information is available on the effects of SDT on glioma stem cells which are key drivers of gliomagenesis and recurrence. To address this, the current study has developed and validated an automated in vitro SDT system to allow the application and mapping of focused ultrasound fields under varied exposure conditions and setup configurations. The study optimizes ultrasound frequency, intensity, plate base material, thermal effect, and the integration of live cells. Indeed, in the presence of 5-ALA, focused ultrasound induces apoptotic cell death in primary patient-derived glioma cells with concurrent upregulation of intracellular reactive oxygen species. Intriguingly, primary glioma stem neurospheres also exhibit remarkably reduced 3D growth upon SDT exposure. Taken together, the study reports an in vitro system for SDT applications on tissue culture-based disease models to potentially benchmark the novel approach to the current standard-of-care.

Results of a hemodialysis vascular access routine ultrasound surveillance protocol and frequency of surveillance guided pre-emptive access maintenance interventions

Background: To evaluate the implementation of routine surveillance using ultrasound on hemodialysis vascular access (VA) outcomes and determine the number and frequency of corrective, surveillance-guided procedures performed. Methods: Multicenter, prospective, observational study that includes consecutive hemodialysis patients receiving therapy from native arteriovenous fistulae (AVF) or grafts (AVG). Participants were assigned to a routine VA Color Doppler ultrasound surveillance (DUS) protocol from January 2019 to December 2021. Patients were referred for corrective procedures (endovascular or surgical) based on clinical or DUS findings (pre-emptive procedures; PEP). Primary endpoint was the estimation of primary unassisted (PUP) and secondary patency (SP) rates. Secondary endpoints were the determination of the number and frequency of PEP and VA survival rates. Results: In total, 223 patients with 243 VA (192 AVF and 51 AVG) were included. Access PUP and SP rates were 83% and 93% at 12 months, 75% and 88% at 24 months, and 72% and 83% at 36 months follow-up. Autologous fistulae PUP and SP were 89% and 96% at 12 months, 81% and 93% at 24 months, and 80% and 89% at 36 months, respectively. Graft PUP and SP were 56% and 80% at 12 months, 44% and 65% at 24 months, and 39% and 54% at 36 months, respectively. In total, 56 corrective procedures (38/56 PEP; 65.5%) were performed (0.13 procedures/year), of which 34 were in AVF patients (0.09 procedures/year) and 22 in AVG patients (0.40 procedures/year). Overall, 33 VA losses occurred (0.06 failures/year), 17 in AVF (0.04 failures/year), and 16 in AVG patients (0.20 failures/year). Conclusion: The use of DUS resulted in the timely diagnosis of dysfunction, satisfactory overall VA survival, and patency rates, with a low PEP frequency. Randomized controlled trials are required to establish the value of DUS surveillance on access patency and whether DUS-guided interventions could improve VA outcomes.

Multimodal image feature fusion for improving medical ultrasound image segmentation

Ultrasound imaging is the most commonly used technique to detect abnormalities of the thyroid and diagnose abnormal breasts. However, due to the inherent characteristics of ultrasound imaging, the contrast of ultrasound images is relatively low, and the tissue boundaries in the image are blurry. This makes it a challenging task to segment thyroid or breast lesions from ultrasound images. In this work, we explore the role of multimodal features at different levels of deep neural network models and their fusion mechanisms for multimodal images generated by ultrasound radio frequency (RF) data. The ultrasound RF data contain information related to the arrangement of scatterers in tissues and organs, which is only partially available in B-mode images. To solve this problem, we use ultrasound RF data to generate parametric images, including Nakagami and entropy images, to illustrate the abundant backscattered statistics contained in RF data. A channel-aware fusion module is proposed to adaptively fuse the features from images of different modalities. Experimental results show that the abundant information contained in RF data can be helpful to identify thyroid glands or breast lesions with low contrast and fuzzy boundaries in B-mode ultrasound images and improve the segmentation performance.

Frequency dependence of ultrasonic effects on the kinetics of hen egg white lysozyme fibrillation

Our study aimed to investigate the effects of ultrasound on the fibrillation kinetics of HEWL (hen egg white lysozyme) and its physicochemical properties. Ultrasound, a mechanical wave, can induce conformational changes in proteins. To achieve this, we developed an ultrasound exposure system and used various biophysical techniques, including ThT fluorescence spectroscopy, ATR-FTIR, Far-UV CD spectrophotometry, Fluorescence microscopy, UV-spectroscopy, and seeding experiments. Our results revealed that higher frequencies significantly accelerated the fibrillation of lysozyme by unfolding the native protein and promoting the fibrillation process, thereby reducing the lag time. We observed a change in the secondary structure of the sonicated protein change to the β-structure, but there was no difference in the Tm of native and sonicated proteins. Furthermore, we found that higher ultrasound frequencies had a greater seeding effect. We propose that the effect of frequency can be explained by the impact of the Reynolds number, and for the Megahertz frequency range, we are almost at the transition regime of turbulence. Our results suggest that laminar flows may not induce any significant change in the fibrillation kinetics, while turbulent flows may affect the process.

Value of contrast-enhanced percutaneous ultrasound in the diagnosis of rotator cuff tear subtype

To explore characteristics of contrast-enhanced ultrasound (CEUS) images features and diagnostic value of rotator cuff tear subtypes. From January 2019 to March 2022, percutaneous ultrasound-guided subacromial bursography (PUSB) with persutaneous ultrasound-guide tendon lesionography (PUTL) was performed on 114 patients with suspected rotator cuff injury were evaluated, including 54 males and 60 females ranged in age from 35 to 75 years old with an average of (58.8±8.7 ) years old;76 patients on the right side and 38 patients on the left side;the course of disease ranged from 0.13 to 111 months with an average of (10.2±9.8) months. GE LOGIQ E9 color doppler ultrasound diagnostic high frequency(6 to 12 MHz) was used to CEUS Using arthroscopy as gold standard, receiver operating characteristic (ROC) curve was used to evaluate diagnostic efficacy of US, MRI and CEUS for rotator cuff injury, also sensitivity, specificity, positive predictive value, negative predictive value and accuracy were calculated. The sensitivity of US in diagnosing full-thickness tears was 72.1%, specificity was 93.0%, and accuracy was 85.1%. The sensitivity, specificity and accuracy of MRI diagnosis of full-thickness tear were 90.9%, 92.6% and 92.1% respectively. The sensitivity, specificity and accuracy of CEUS in diagnosis of full-thickness tear were 100%. The sensitivity, specificity and accuracy of US in the diagnosis of partial tear were 85.7%, 77.2% and 79.8% respectively. The sensitivity, specificity and accuracy of MRI diagnosis of partial tear were 83.7%, 81.7% and 82.5% respectively. The sensitivity, specificity and accuracy of CEUS in diagnosis of partial tear were 95.7%, 92.6% and 93.9% respectively. There were significant differences in diagnosis results of US, MRI and CEUS for rotator cuff bursa tear (P<0.001). Kapp test showed good consistency between CEUS and arthroscopy in diagnosing rotator cuff tear subtypes (full-thickness and partial tears). Using PUSB/PUTL to observe distribution of contrast media in bursa, tendon and joint cavity to evaluate the type of rotator cuff tear, its diagnostic performance is significantly better than US and MRI. Therefore, percutaneous contrast-enhanced ultrasound can be a reliable method for diagnosing subtypes of rotator cuff tears.

Polymer Mechanochemistry in Microbubbles.

Polymer mechanochemistry is a promising technology to convert mechanical energy into chemical functionality by breaking covalent and supramolecular bonds site-selectively. Yet, the mechanochemical reaction rates of covalent bonds in typically used ultrasonication setups lead to reasonable conversions only after comparably long sonication times. This can be accelerated by either increasing the reactivity of the mechanoresponsive moiety or by modifying the encompassing polymer topology. Here, a microbubble system with a tailored polymer shell consisting of an N2 gas core and a mechanoresponsive disulfide-containing polymer network is presented. It is found that the mechanochemical activation of the disulfides is greatly accelerated using these microbubbles compared to commensurate solid core particles or capsules filled with liquid. Aided by computational simulations, it is found that low shell thickness, low shell stiffness and crosslink density, and a size-dependent eigenfrequency close to the used ultrasound frequency maximize the mechanochemical yield over the course of the sonication process.

Desynchronization of neuronal firing in multiparameter ultrasound stimulation

Low-intensity transcranial ultrasound stimulation, a novel neuromodulation technique, that possesses the advantages of non-invasiveness, high penetration depth, and high spatial resolution, has achieved positive neuromodulation effects in animal studies. But the regulatory mechanism remains controversial. The intramembrane cavitation effect is considered one of the mechanisms for ultrasound neuromodulation. In this study, the modified equations of ultrasonic cavitation bubble dynamics were coupled with the dual-coupled neuron Hindmarsh-Rose model, small-world neural network model, and the Jansen-Rit neural mass model, which simulate simple coupled neurons, complex neuronal networks, and discharge signals in epileptic disorders respectively. The results demonstrated that ultrasound stimulation has an appreciable modulatory effect on neuronal firing desynchronization in Hindmarsh-Rose model and small-world neural network model. The desynchronization effect is related to the stimulation frequency and intensity. Furthermore, ultrasound stimulation has an inhibitory effect on epileptic seizures, and the effect is enhanced by increasing ultrasound frequency from 0.1–1.0 MHz. This is the first combination of ultrasonic intramembrane cavitation effect theory with neurons and neural network firing desynchronization, which can provide guidance of parametric and theories support for the studies of neurological diseases such as epilepsy and Parkinson’s disease.

Contrast Agent-Free 3D Renal Ultrafast Doppler Imaging Reveals Vascular Dysfunction in Acute and Diabetic Kidney Diseases.

To combat the irreversible decline in renal function associated with kidney disease, it is essential to establish non-invasive biomarkers for assessing renal microcirculation. However, the limited resolution and/or vascular sensitivity of existing diagnostic imaging techniques hinders the visualization of complex cortical vessels. Here, a 3D renal ultrafast Doppler (UFD) imaging system that uses a high ultrasound frequency (18MHz) and ultrahigh frame rate (1KHz per slice) to scan the entire volume of a rat's kidney in vivo is demonstrated. The system, which can visualize the full 3D renal vascular branching pyramid at a resolution of 167µm without any contrast agent, is used to chronically and noninvasively monitor kidneys with acute kidney injury (AKI, 3 days) and diabetic kidney disease (DKD, 8 weeks). Multiparametric UFD analyses (e.g., vessel volume occupancy (VVO), fractional moving blood volume (FMBV), vessel number density (VND), and vessel tortuosity (VT)) describe rapid vascular rarefaction from AKI and long-term vascular degeneration from DKD, while the renal pathogeneses are validated by in vitro blood serum testing and stained histopathology. This work demonstrates the potential of 3D renal UFD to offer valuable insights into assessing kidney perfusion levels for future research in diabetes and kidney transplantation.

A level-set method for ultrasound-driven bubble motion and tissue deformation

Ultrasound-driven bubble collapse and resulting tissue deformation are numerically investigated by combining a level-set method for determining the liquid–gas and liquid–solid interfaces and a full Eulerian method to solve the unified governing equations for both solid and fluid phases. The fluid compressibility effect is considered by employing the van der waals and Tait equations of state for gas and liquid, respectively, and a semi-implicit pressure correction method is used to effectively capture ultrasound and shock waves. Two tissue models, treating tissue as a viscoelastic solid or as a fluid with large surface tension, are compared in terms of the bubble expansion and compression processes and tissue deformation patterns. Computations are also carried out to investigate the influences of ultrasonic pulse amplitude, ultrasound frequency, and bubble-tissue distance on the bubble-tissue interaction.