Ultrasound Cavitation Research Articles

Effect of Compressive Residual Stress on Film Formed by Mechanochemical Multifunction Cavitation Processing

Recently, mechanochemical multifunction cavitation (MC-MFC) was developed to improve the corrosion resistance of the magnesium surface. MFC is a technology that combines water jet peening and ultrasound cavitation. MC-MFC is a technology that adds phosphoric acid to water. It can improve the corrosion resistance by forming a phosphate film on the Mg surface. Conventional anodic oxidation, plating, and chemical vapor deposition can improve corrosion resistance by forming a film on the Mg surface, but it is difficult to improve characteristics such as compressive residual stress on the surface. MFC-treated surfaces have previously imparted various properties such as imparting compressive residual stress necessary to improve the fatigue strength to Al alloys and Cr-Mo steels. In this study, the effect of film formed on MC-MFC processed surface on compressive residual stress was investigated.

Sudden Cell Death Induced by Ca2+ Delivery via Microbubble Cavitation.

Intracellular calcium ion delivery via sonoporation has been validated to be a substitute for classical chemotherapy. However, the mechanism behind calcium sonoporation remains unclear to this day. To elucidate the role of calcium in the process of sonoporation, we aimed to investigate the influence of different calcium concentration on cell membrane permeabilization and cell viability after sonoporation. In this study, we present experimental evidence that extracellular calcium plays a major role in cell membrane molecular transport after applying ultrasound pulses. Ultrasound-microbubble cavitation in the presence of different calcium concentration affects fundamental cell bio-physio-chemical conditions: cell membrane integrity, metabolic activity, and colony formation. Corresponding vital characteristics were evaluated using three independent viability tests: propidium iodide assay (20 min–3 h), MTT assay (48 h), and cell clonogenic assay (6 d). The results indicate instant cell death, as the level of cell viability was determined to be similar within a 20 min–48 h–6 d period. Inertial cavitation activities have been determined to be directly involved in calcium delivery via sonoporation according to high correlation (R2 > 0.85, p < 0.01) of inertial cavitation dose with change in either cell membrane permeabilization, metabolic activity, and colony formation efficiency. In general, calcium delivery via sonoporation induces rapid cell death, occurring within 20 min after treatment, that is the result of ultrasound mediated microbubble cavitation.

Acoustic Optimization of a Flow Through Ultrasonic Cavitation Reactor for Treatment of Cellulose Fibers

In pulp and paper manufacturing cellulose fibers are modified in various process steps to obtain an end product with certain specifications. In this chain of interlinked processes, the mechanical refining stage has a significant impact on modifying the properties of the fiber wall. However, refining is identified as the most energy intensive process in paper manufacturing and in order to reduce the energy use for a more sustainable process, the development of alternative refining methods are of increasing interest. Ultrasound cavitation has proved to be a efficient refining process but so far it is limited to small volumes and batch process’s. The developed ultrasonic reactor is capable of handling larger fiber volumes in a continuous, scalable, flow process. The proposed method could therefore be an alternative and efficient way of processing fibers to minimize energy usage and waste. In this study, both numerical simulations and experiments are combined and analysed to establish a design of a scalable, flow-through ultrasound reactor. The implemented model is based on the linearized wave equation in the frequency domain with appropriate addition of nonlinear attenuation by cavitation bubbles. The influence of ultrasound cavitation was experimentally verified by characterization of the modification of CTMP softwood cellulose fiber properties. Results shows that the proposed method using ultrasound cavitation can modify the fiber’s mechanical properties at energy levels of 804 kWh/bdt. However, there was no significant change in paper strength properties as per ISO 1924-3.

Modification of Olive Leaves’ Surface by Ultrasound Cavitation. Correlation with Polyphenol Extraction Enhancement

We investigated the impact of ultrasound at 20 kHz on olive leaves to understand how acoustic cavitation could increase polyphenol extraction. Application of ultrasound to whole leaf from 5 to 60 min enabled us to increase extraction from 6.96 to 48.75 µg eq. oleuropein/mL of extract. These results were correlated with Environmental Scanning Electron Microscopy, allowing for leaf surface observation and optical microscopy of treated leaf cross sections to understand histochemical modifications. Our observations suggest that the effectiveness of ultrasound applied to extraction is highly dependent on plant structure and on how this material will react when subjected to acoustic cavitation. Ultrasound seems to impact the leaves by two mechanisms: cuticle erosion, and fragmentation of olive leaf surface protrusions (hairs), which are both polyphenol-rich structures.

Surgical treatment of wounded persons with complicated thoracic damages

Objective. To improve the results of complex surgical treatment of wounded and injured persons with thoracic trauma, complicated by bronchopleural fistulas, pleural empyema and defects in the thoracic wall soft tissues, basing on introduction of the proposed procedure of vacuum therapy in combination with bronchoscopic obturation of certain bronchus.&#x0D; Materials and methods. Analysis of results of the complex surgical help delivery for 54 wounded persons with defects of the thoracic wall soft tissues, broncho-pleural fistulas and pleural empyema, caused by the combat thoracic trauma, on ІІІ and ІV levels of medical support while conduction of the Antiterrorist operation/Operation of the Joined Forces (the main group) and 73 injured persons with thoracic trauma of the peace period (the comparison group) in the 2014 - 2019 yrs period was conducted.&#x0D; Results. Improvement of complex surgical treatment of the wounded and damaged persons with thoracic trauma and defects of the thoracic wall soft tissues have permitted to reduce the complications frequency by 6.7%, and lethality - by 9.2% in the main group.&#x0D; Conclusion. There was proposed a procedure of vacuum therapy, ultrasound cavitation together with bronchoscopic bronchial obturation for its fistula, which have proved its efficacy in complex surgical treatment of severely wounded persons with the gun-shot thoracic damages and presence of combination of pleural empyema, bronchial fistula and defects of soft tissues.

Comment on "Bulk Nanobubbles or Not Nanobubbles: That is the Question".

In a recent article, Jadhav and Barigou ( Langmuir 2020, 36 (7), 1699-1708) investigated the question of the existence of stable bulk nanobubbles in water generated by hydrodynamic cavitation, ultrasound cavitation, and the addition of an organic compound (namely, ethanol) to water. They firmly conclude that these procedures result in stable bulk nanobubbles. However, a number of previous works documented that the nanoentities observed in water upon such procedures are not nanobubbles. Here, we analyze work of Jadhav and Barigou and show that conclusions regarding the nanobubble nature of the nanoentities are incorrect and are due to the choice of experimental techniques with weak sensitivity, methodical issues in the use of otherwise proper experimental techniques, and ambiguous outcomes of the rest of experiments.

Use of high-power ultrasound combined with supercritical fluids for microbial inactivation in dry-cured ham

The aim of this study was to analyze the application of supercritical carbon dioxide combined with high-power ultrasound (SC-CO2 + HPU) and the use of a saline solution (SS; 0.85% NaCl) on the microbial inactivation and the quality of dry-cured ham. The effect of temperature, pressure and treatment time was studied using RSM. Physicochemical analyses were carried out after the treatments and during refrigerated storage (30 days / 4 °C). The most significant inactivation of Escherichia coli (3.62 ± 0.20-log CFU/g) was obtained using the SC-CO2 + HPU + SS (25 MPa, 46-°C and 10-min), with temperature being the most important process variable. Fat content showed a significant (p < 0.05) reduction (46%) after the SC-CO2 + HPU treatment. The breakage of the muscle fibers, the disorganization in the myofibrils, as well as the enlargement of the interfibrillar spaces led to the ham softening (avg 26.5%). No significant (p > 0.05) changes in color, texture or pH were found during storage. Thus, ultrasonic-assisted SC-CO2 could be used, in combination or not with SS, to improve the shelf of dry-cured ham. Industrial relevanceSupercritical carbon dioxide (SC-CO2) inactivation technology has been shown to be highly efficient at reducing different bacteria in liquid media with minimum effect on food quality. This technology is barely applied to solid products and its use is limited by the long processing times and reduced inactivation capacity. The application of high-power ultrasound (HPU) leads to a shorter process time. This technology is useful for the inactivation of ham microbiota and inoculated E.coli. A liquid medium surrounding the treated solid can enhance microbial inactivation for the purposes of improving the effect of ultrasound cavitation, while only minimally affecting the quality of the samples (color, texture, fat and moisture contents).

The effect of ultrasound cavitation in combination with cryolipolysis as a non-invasive selective procedure for abdominal fat reduction

Background and aimFat reduction and body contouring have become popular procedures in the cosmetic surgery industry over the past decade. There have been studies to replace invasive methods such as liposuction, with safer non-invasive procedures. We aimed to evaluate the effect of a non-invasive combination therapy of ultrasound cavitation and cryolipolysis on abdominal adipose tissue. MethodsThis pilot interventional study comprised 90 female individuals aged 18-65-years-old who were recruited into one of three groups of 30 participants. Group 1 was treated with diet alone (the control group), group 2 with cryolipolysis and diet, and group 3 with a combination of ultrasound cavitation, cryolipolysis, and diet for 8 weeks. Anthropometric parameters were measured before, during, and after the trial included total body weight, body mass index(BMI), body fat mass, fat-free mass, and abdomen circumference. ResultsAll three groups demonstrated significant reductions in each parameter at the end of the intervention (P < 0.01). Apart from fat-free mass (P = 0.66), the combination therapy significantly reduced body fat mass, weight, BMI, and abdomen circumference compared to the control group (P < 0.01). There was no significant difference between the combination therapy and cryolipolysis-alone groups. ConclusionTreatment using a combination of cryolipolysis and ultrasound cavitation is no more effective in improving the anthropometric indices than cryolipolysis alone.

Ultrasound‐Assisted Green Synthesis of Ag‐Decorated ZnO Nanoparticles UsingExcoecaria agallochaLeaf Extract and Evaluation of Their Photocatalytic and Biological Activity

AbstractThe present study deals with the synthesis of ZnO and Ag‐ZnO nanoparticles using Excoecaria agallocha leaf extract under a controlled ultrasound cavitation technique. The characterization of the as‐synthesized ZnO and Ag‐ZnO nanoparticles (different molar concentration of Ag) were subjected to Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction analysis (XRD), UV‐Visible Diffuse reflectance spectroscopy (UV‐Vis DRS), Thermogravimetric analysis (TGA), N2 adsorption‐desorption isotherm (BET), scanning electron microscopy(SEM) and transmission electron microscopy (TEM). The photocatalytic performance of ZnO and Ag‐ZnO nanoparticles as catalysts were studied for hazardous organic dyes such as methylene blue (MB) and rhodamine‐B (Rh−B) under solar light irradiation. The degradation study follows pseudo‐first‐order kinetics. The effective degradation of MB was found to be 56.44 % (ZnO nanoparticles) and 98.44 % Ag‐ZnO nanoparticles, respectively at 100 min at the molar ratio (0.25 : 1). Whereas, Rh−B shows 27.50 % (ZnO nanoparticles) and 98.83 % at the same molar ratio of Ag‐ZnO nanoparticles at 80 min. Among the as‐synthesized nanoparticles, Ag‐ZnO at molar ratio 0.25 : 1 shows effective photocatalytic activity. Besides these as‐synthesized nanoparticles exhibited good antimicrobial activity with an increase in Ag nanoparticles decorated into ZnO. A similar trend was observed in antioxidant and anti‐inflammatory activity.

Склерозивний лишай вульви: сучасні уявлення про клінічні прояви, діагностику і методи лікування (Аналітичний огляд та власний досвід)

Sclerosing lichen is one of the most common pathophysiological conditions observed in the peri-and postmenopausal periods. This problem is relevant because the clinical symptoms of the disease associated with atrophy (dryness, itching in the vagina and vulva, dyspareunia, dysuria) occur in more than 40% of patients aged over 50 years old. Nowadays the problem of maintaining health and preventing diseases caused by aging has become a central one. An in-depth analysis and systematization of key issues related to the precancerous pathology of the vulva have been conducted in this article. The first part of the publication covers main issues of epidemiology, etiology, pathogenesis and modern classification of sclerotic lichen, the second part presents the main aspects of the clinical picture, differential diagnosis and methods of disease diagnosis. The most effective and relevant treatments are under consideration in the third part of the article. Particular emphasis is made on the use of destructive techniques based on the use of laser technology and other approaches based on the use of physical factors (laser therapy, laser coagulation, cryodestruction). An important role among them is played by such an option as photodynamic therapy – a method of treatment based on the combined use of special substances (photosensitizers) and laser radiation with a certain wavelength. The authors report that only a comprehensive approach in this pathology treatment is the key to success in combating the main symptoms of the disease, and such an approach is a solution to the issue of effective prevention of vulvar cancer. The detailed information presented in the article is relevant, it can be extremely important for gynecologists, as well as professionals involved in solving problems related to sclerotic lichen. Keywords: sclerosing lichen, vulva, low-frequency ultrasound cavitation, photodynamic therapy.

MULTIMODAL APPROACH IN THE RECONSTRUCTION OF FIRING DEFECTS OF THE LOWER LIMBS (CLINICAL CASE)

According connection with the global trends, manifested by an increase in the number of illegal firearms, an increase in social, political, ethnic, racial and religious conflicts, accompanied by the use of firearms, the problem of treating gunshot wounds is becoming increasingly important. It is especially acute during local and widespread hostilities, during peacekeeping missions, anti-terrorist operations, in cases of massive gunshot wounds. The aim of the work is to improve the surgical tactics in the reconstruction of severe wounded with soft tissue gunshot defects due to the multimodal scheme. Improvement of dynamic audio and thermal imaging diagnostics of the damaged anatomical area, analysis and modeling of the shape and direction of movement of the donor flap. A clinical case of closure of a bullet-through bullet wound of the left thigh (03.25.19 year) with a gunshot multi-fragment fracture of the left femoral pigtail in the middle third, damage to the superficial femoral vein and marginal damage to the superficial femoral artery was demonstrated.In the preoperative period, the first stage was dynamic digital thermography of the surface of wounds and surrounding soft tissues, which allowed thermal imaging to assess the state of damaged structures, to identify areas of preservation of blood supply. The second stage was the audio control of the identified areas of the "supply" - perforating vessels with a comparison of the blood flow velocity. The results obtained formed the basis for modeling the donor zone and monitoring its movement. The described clinical case of soft tissue defect closure consisted of three stages: The first stage - preparatory (diagnostics and cleaning) - (9 days of inpatient treatment) - repeated surgical treatment of wounds using low-frequency ultrasound (cavitation of the wound surface), controlled negative pressure (in a pulsed mode - 125 mm Hg), the imposition of secondary early sutures, due to which the wound area decreased by 35% compared to the wound area at the time of admission to the VICC of the Southern region. The second stage - the final (reconstructive) - (12 days after the injury) - plastic reconstruction of the defect of the posterior surface of the middle third of the left thigh by moving a ball-and-socket flap from the outer surface of the thigh using the Keystone technique. Conclusions: A multimodal algorithm with dynamic control of changes in the perfusion of the defect zone and surrounding structures is at the heart of the successful reconstruction of a gunshot defect in the soft tissues of the lower extremities, which reduces the treatment time by 1.5 times.

CT-based simulation of ultrasound propagation and cavitation in the human body for the assessment of acoustic therapy monitoring in high intensity focused ultrasound

In situ control of therapy parameters based on real time monitoring of ablation targets is a promising strategy to improve the safety and efficacy of extracorporeal high-intensity focused ultrasound (HIFU). In this work, we present an approach to evaluate the accuracy of acoustic monitoring techniques using computational fluid dynamics simulation. In the numerical setup, computed tomography images are used to model anatomical structures that can scatter and dissipate therapy waves in the body of the patient, including fat, bone, tissues, and organs. An in-house, compressible flow solver is used to simulate ultrasound generation from a transducer, nonlinear focusing of the wave toward therapy targets in the body, and backscattering toward the body surface. The simulation also captures excitation of cavitation bubbles in the focal region and their influence on the pressure fields in the body. Sensing and processing of the scattered signals provide for acoustic monitoring. For demonstration, we apply this approach to HIFU-based lithotripsy that uses burst waves with a focal pressure of O(1) MPa and frequency of O(100) kHz. Accuracies of acoustic monitoring are compared for various sensing and signal processing methods in quantifying the effects of anatomical structures and cavitation on ultrasound irradiation into targeted kidney stones. Finally, we discuss the use of these numerical experiments for control and optimization of therapy parameters. [Work supported by NIH P01-DK043881.]

Effect of intensifying additives on the degradation of thiamethoxam using ultrasound cavitation

The present study has investigated the degradation of thiamethoxam using ultrasound cavitation (US) operated at a frequency of 20 kHz and its combination with intensifying additives viz. hydrogen peroxide, Fenton and photo-Fenton reagent. At the outset, the performance of US (20 kHz) has been maximised by the optimization of process parameters. Highest rate of degradation of thiamethoxam was observed at the optimum ultrasonic power density of 0.22 W/mL, thiamethoxam concentration of 10 ppm and the pH of 2. The established optimum values of operating parameters were used further in case of combined treatment approaches. The effect of concentration of H2O2 on the rate of degradation of thiamethoxam in the case of US + H2O2 process has confirmed the existence of optimum concentration of H2O2 with the ratio of thiamethoxam: H2O2 as 1:10. US + Fenton process indicated the optimal molar ratio of FeSO4·7H2O:H2O2 as 1:15. The combined processes of US + H2O2, US + Fenton and US + photo-Fenton have resulted in the extent of degradation of 20.47 ± 0.61%, 34.41 ± 1.03% and 85.17 ± 2.56% respectively after 45 min. of operation. These combined processes lead to the synergistic index of 2.04 ± 0.06, 2.26 ± 0.07 and 2.42 ± 0.07 in case of US + H2O2, US + Fenton and US + photo-Fenton processes respectively over only US/stirring treatment with the additive. Additionally, the extent of mineralization and the energy efficiency of individual and combined processes have been compared. US + photo-Fenton process has been found to be the best strategy for effective degradation of thiamethoxam with a significant intensification benefit. The by-products formed during the ultrasonic degradation of thiamethoxam have been identified by using LC-MS/MS analysis.

Co-Immobilization of Ce6 Sono/Photosensitizer and Protonated Graphitic Carbon Nitride on PCL/Gelation Fibrous Scaffolds for Combined Sono-Photodynamic Cancer Therapy.

Aiming at developing a moderate and efficient sono-photodynamic therapy for breast cancer, tissue engineering scaffolds may provide an easy and efficient strategy to eliminate serious side effects in conventional surgery or chemotherapy, and thus, they are highly desired. However, the development of ideal sono-photodynamic therapeutic scaffolds is always hindered by the poor stability and incompatibility between the different biomaterial components. Herein, the Food and Drug Administration (FDA)-approved sono/photosensitizer Chlorin e6 (Ce6) was successfully and tightly incorporated into electrospun polycaprolactone/gelatin (PG) scaffolds via positively charged protonated g-C3N4 nanosheets (pCN). The PG fibers were precoated with graphene oxide (GO) to enable the assembly of pCN on the surface through electrostatic interactions. The Ce6@pCN-GO-PG composite scaffolds exhibited good cytocompatibility and excellent sono-photodynamic activity, leading to distinctly boosted reactive oxygen species (ROS) generation and a 95.8% inactivation rate of breast cancer cells through a synergistic sono-photodynamic process triggered by an 808 nm laser and 1 MHz ultrasound (US) excitation, within the clinical therapeutic dose. The as-developed scaffolds with unique ultrasound cavitation therapeutic effects can be used not only for complete eradication of tumor cells after surgery but also as a cell behavior observation platform of sono-photodynamic cancer therapy.

Enhanced degradation of total petroleum hydrocarbons in real soil by dual-frequency ultrasound-activated persulfate

Ultrasound (US) can be employed to activate persulfate (PS) for degrading total petroleum hydrocarbons (TPH). In this study, to improve the degradation efficiency, PS is combined with dual-frequency US (DFUS) towards synergistic degradation of TPH in real soil. After 180 min, the degradation percentages for DFUS/PS, DFUS, high-frequency US and high-frequency US/PS are around 88.9%, 38.7%, 7.3% and 54.2%, respectively. Additionally, the influence of US power, PS content, slurry pH and temperature, and TPH components on the degradation percentage in the DFUS/PS process are explored. Scanning electron microscopy (SEM) images and the results of specific surface area verify that the DFUS can break the soil aggregates more effectively than the single-frequency US, and thus enhance the TPH desorption and accelerate the oxidant diffusion. Moreover, the investigation of the mechanism is further evaluated through quenching and electron spinning resonance spectrum (ESR) tests. The results indicate that the generation of SO4− and OH in DFUS/PS is ~1.6 times and ~2.5 times as much, respectively, as in high frequency US/PS. The relative contributions to the synergistic TPH degradation in the DFUS/PS system are: SO4− (PS activation via the heat induced by US) > pyrolysis inside the bubbles (hydrophobicity of TPH) > SO4− (PS activation via US cavitation) >OH. Finally, the hypothesis is confirmed via the evaluation of the degradation kinetics, which shows that the combined process of DFUS/PS is not a simple addition of the US and PS, but provides a highly effective process of synergistic degradation.

Simulation and exploration of cavitation process during microalgae oil extracting with ultrasonic-assisted for hydrogen production

Microalgae is promising to be used as feedstock resources for hydrogen production due to its high oil and grease contents. This promotes the development of extraction technology of microalgae oil. In this study, based on the Rayleigh-Plesset equation, the effects of temperature, pressure, ultrasonic power and frequency on the bubble motion of ethanol ultrasound cavitation are investigated. Subsequently, the effects of different process parameters on the extraction rate are studied using Schizochytrium sp. as raw material by stirring or ultrasonic-assisted extraction. And the composition of algae extraction oil is analyzed. The results show that the amplitude of cavitation bubbles increases with the increase of ultrasonic power and decrease of ultrasonic frequency. The extraction rate of algae oil reaches 93.76 ± 0.48% when the ultrasonic power is 150 W, the reaction time is 30 min, the temperature is 50 °C and the liquid-solid ratio is 10:1.

Cavitation-Enhanced Delivery of the Nanomaterial Graphene Oxide-Doxorubicin to Hepatic Tumors in Nude Mice Using 20 kHz Low-Frequency Ultrasound and Microbubbles

Graphene oxide (GO) is a kind of nanomaterial. Here, we explored its application in tumor treatment. We loaded doxorubicin onto the surface of GO to form graphene oxide-doxorubicin (GO-DOX). After injection of the contrast agent SonoVue microbubbles (MBs) into the tail vein of tumor-bearing nude mice, subcutaneous hepatic carcinomas inoculated with the HepG2 cell line were irradiated with 20 kHz low-frequency ultrasound (US). Subsequently, GO-DOX was injected into the tail vein of nude mice. Transmission electron microscopy (TEM) and TUNEL assays were performed to observe the curative effects. Biocompatibility tests of GO-DOX included routine blood cell counts, blood smears, serum biochemical assays, and histological sampling of important organs. It was found that the nanomaterial GO-DOX promoted apoptosis of tumor cells in nude mice. TEM of the USMB+GO-DOX treatment showed vascular endothelial cell wall rupture, widened endothelial cell gaps, black granules in the vascular lumen, interstitial erythrocyte leakage, and apparent apoptosis of tumor cells. There were no toxic side effects of GO-DOX on the blood system and in the major organs of these mice. Ultrasound cavitation destroys tumor blood vessels and enhances the release of nanomaterials to tumor cells of nude mice.

Ultrasound cavitation enhanced chemotherapy: In vivo research and clinical application.

The novelty of this research is that we used ultrasound cavitation to enhance the effects of chemotherapy in the subcutaneous and orthotopic hepatic carcinomas in nude mice. Case reports of the effects of the targeting ultrasound cavitation and chemotherapy on malignant tumors in clinical patients were also examined. We found that low-frequency ultrasound cavitation combined with chemotherapy is effective in the inhibition of tumor growth to some extent.

Cavitation bubble collapse in a vicinity of a liquid-liquid interface – Basic research into emulsification process

The initial motivation for the study was to gain deeper understanding into the background of emulsion preparation by ultrasound (cavitation). In our previous work (Perdih et al., 2019) we observed rich phenomena occurring near the liquid-liquid interface which was exposed to ultrasonic cavitation. Although numerous studies of bubble dynamics in different environments (presence of free surface, solid body, shear flow and even variable gravity field) exist, one can find almost no reports on the interaction of a bubble with a liquid-liquid interface. In the present work we conducted a number of experiments where single cavitation bubble dynamics was observed on each side of the oil-water interface. These were accompanied by corresponding simulations. We investigated the details of bubble interface interaction (deformation, penetration). As predicted, by the anisotropy parameter the bubble always jets toward the interface if it grows in the lighter liquid and correspondingly away from the interface if it is initiated inside the denser liquid. We extended the analysis to the relationships of various bubble characteristics and the anisotropy parameter.Finally, based on the present and our previous study (Perdih et al., 2019), we offer new insights into the physics of ultrasonic emulsification process.

Flow Augmentation in the Myocardium by Ultrasound Cavitation of Microbubbles: Role of Shear-Mediated Purinergic Signaling

Ultrasound-mediated cavitation of microbubble contrast agents produces high intravascular shear. We hypothesized that microbubble cavitation increases myocardial microvascular perfusion through shear-dependent purinergic pathways downstream from ATP release that is immediate and sustained through cellular ATP channels such as Pannexin-1. Quantitative myocardial contrast echocardiography perfusion imaging and invivo optical imaging of ATP was performed in wild-type and Pannexin-1-deficient (Panx1-/-) mice before and 5 and 30minutes after 10minutes of ultrasound-mediated (1.3MHz, mechanical index 1.3) myocardial microbubble cavitation. Flow augmentation in a preclinical model closer to humans was evaluated in rhesus macaques undergoing myocardial contrast echocardiography perfusion imaging after high-power cavitation in the apical four-chamber plane for 10minutes. Microbubble cavitation in wild-type mice (n=7) increased myocardial perfusion by 64%±25% at 5minutes and 95%±55% at 30minutes compared with baseline (P<.05). In Panx1-/- mice (n=5), perfusion increased by 28%±26% at 5minutes (P=.04) but returned to baseline at 30minutes. Myocardial ATP signal in wild-type (n=7) mice undergoing cavitation compared with sham-treated controls (n=3) was 450-fold higher at 5minutes and 90-fold higher at 30minutes after cavitation (P<.001). The ATP signal in Panx1-/- mice (n=4) was consistently 10-fold lower than that in wild-type mice and was similar to sham controls at 30minutes. In macaques (n=8), myocardial perfusion increased twofold in the cavitation-exposed four-chamber plane, similar in degree to that produced by adenosine, but did not increase in the control two-chamber plane. Cavitation of microbubbles in the myocardial microcirculation produces an immediate release of ATP, likely from cell microporation, as well as sustained release, which is channel dependent and responsible for persistent flow augmentation. These findings provide mechanistic insight by which cavitation improves perfusion and reduces infarct size in patients with myocardial infarction.