Microbubbles and Ultrasound Accelerated Thrombolysis for Peripheral Arterial Occlusions: The Outcomes of a Single Arm Phase II Trial.

OBJECTIVE: Acute peripheral arterial occlusions can be treated by catheter directed thrombolysis (CDT). However, CDT is time consuming and accompanied by the risk of bleeding complications. The addition of contrast enhanced ultrasound and microbubbles could improve thrombus susceptibility to thrombolytic agents and potentially shorten treatment time with a lowered risk of bleeding complications. This article reports the outcomes of the safety and feasibility of this novel technique. METHODS: In this single arm phase II trial, 20 patients with acute lower limb ischaemia received CDT combined with an intravenous infusion of microbubbles and locally applied ultrasound during the first hour of standard intra-arterial thrombolytic therapy. The primary endpoint was safety, i.e., occurrence of serious adverse events (haemorrhagic complications and/or amputation) and death within one year. Secondary endpoints included angiographic and clinical success, thrombolysis duration, additional interventions, conversion, and quality of life. RESULTS: The study included 20 patients (16 men; median age 68.0 years; range, 50.0 - 83.0; and 40% native artery and 60% bypass graft). In all patients, the use of microbubble contrast enhanced sonothrombolysis could be applied successfully. There were no serious adverse events related to the experimental treatment. Duplex examination showed flow distal from the occlusion after 23.1 hours (range 3.1 - 46.5) with a median thrombolysis time of 47.5 hours (range 6.0 - 81.0). The short term ABI and pain scores significantly improved; however, no changes were observed before or after thrombolysis in the microcirculation. Overall mortality and amputation rates were both 2% within one year. The one year patency rate was 55%. CONCLUSION: Treatment of patients with acute peripheral arterial occlusions with contrast enhanced sonothrombolysis is feasible and safe to perform in patients. Further research is necessary to investigate the superiority of this new treatment over standard treatment.

Non-invasive, neurotoxic surgery reduces seizures in a rat model of temporal lobe epilepsy.

Surgery can be highly effective for treating certain cases of drug resistant epilepsy. The current study tested a novel, non-invasive, surgical strategy for treating seizures in a rat model of temporal lobe epilepsy. The surgical approach uses magnetic resonance-guided, low-intensity focused ultrasound (MRgFUS) in combination with intravenous microbubbles to open the blood-brain barrier (BBB) in a transient and focal manner. During the period of BBB opening, a systemically administered neurotoxin (Quinolinic Acid: QA) that is normally impermeable to the BBB gains access to a targeted area in the brain, destroying neurons where the BBB has been opened. This strategy is termed Precise Intracerebral Non-invasive Guided Surgery (PING). Spontaneous recurrent seizures induced by pilocarpine were monitored behaviorally prior to and after PING or under control conditions. Seizure frequency in untreated animals or animals treated with MRgFUS without QA exhibited expected seizure rate fluctuations frequencies between the monitoring periods. In contrast, animals treated with PING targeting the intermediate-temporal aspect of the hippocampus exhibited substantial reductions in seizure frequency, with convulsive seizures being eliminated entirely in two animals. These findings suggest that PING could provide a useful alternative to invasive surgical interventions for treating drug resistant epilepsy, and perhaps for treating other neurological disorders in which aberrant neural circuitries play a role.

Neural network-based modeling of the number of microbubbles generated with four circulation factors in cardiopulmonary bypass.

The need for the estimation of the number of microbubbles (MBs) in cardiopulmonary bypass surgery has been recognized among surgeons to avoid postoperative neurological complications. MBs that exceed the diameter of human capillaries may cause endothelial disruption as well as microvascular obstructions that block posterior capillary blood flow. In this paper, we analyzed the relationship between the number of microbubbles generated and four circulation factors, i.e., intraoperative suction flow rate, venous reservoir level, continuous blood viscosity and perfusion flow rate in cardiopulmonary bypass, and proposed a neural-networked model to estimate the number of microbubbles with the factors. Model parameters were determined in a machine-learning manner using experimental data with bovine blood as the perfusate. The estimation accuracy of the model, assessed by tenfold cross-validation, demonstrated that the number of MBs can be estimated with a determinant coefficient R2 = 0.9328 (p < 0.001). A significant increase in the residual error was found when each of four factors was excluded from the contributory variables. The study demonstrated the importance of four circulation factors in the prediction of the number of MBs and its capacity to eliminate potential postsurgical complication risks.

Silicone microbubbles after anti-vascular endothelial growth factor injections in patients with wet age-related macular degeneration: incidence, quantification and secondary optical coherence tomography artfacts.

PURPOSE: To report the incidence and quantity of silicone oil microbubbles and the relationship with the number of intravitreal anti-vascular endothelial growth factor (VEGF) injections and evaluate if microbubbles induce artefacts on optical coherence tomography (OCT) images. METHODS: Observational, descriptive, cross-sectional study. Patients with wet age-related macular degeneration were included who had been treated for 1 year minimally with anti-VEGF injections repackaged in the hospital pharmacy. Detection and quantification of silicone microbubbles by mydriatic biomicroscopic examination were conducted 1 month after the last injection. The numbers of microbubbles were quantified on a scale of 0-3: 0, none; 1 scarce (1-10 microbubbles); 2 moderate (10-30); or 3 numerous (>30). Shadowing on OCT images was classified as 0-3: 0, none; 1 obscuring some retinal layers; 2 obscuring all retinal layers; or 3 obscuring the retinal thickness. RESULTS: The study included 142 eyes of 98 patients (mean age, 82.4 years + 7.3; range, 65-97) treated with 2377 injections. Microbubbles were detected in 127 (89.4%) eyes, 62 (43.6%) with numerous microbubbles and 36 (25.4%) and 29 (20.4%), respectively, with scarce and moderate numbers. A positive correlation was found between the numbers of injections and intravitreal silicone (rho, 0.7). Optical coherence tomography (OCT) artefacts were detected in 11 eyes; the artefacts obscured all retinal layers in three eyes. No significant relationship could be established between the appearance of floaters and the microbubbles. CONCLUSION: The presence and number of silicone microbubbles were correlated with the number of intravitreal injections. Microbubbles can produce OCT artefacts, which can hinder the treatment decision.

Microbubble-Facilitated Ultrasound Catheter Ablation Causes Microvascular Damage and Fibrosis.

High-intensity ultrasound (US) ablation produces deeper myocardial lesions than radiofrequency ablation. The presence of intravascular microbubble (MB) contrast agents enhances pulsed-wave US ablation via cavitation-related histotripsy, potentially facilitating ablation in persistently perfused/conducting myocardium. US ablation catheters were developed and tested in the presence of MBs using ex vivo and in vivo models. High-frame-rate videomicroscopy and US imaging of gel phantom models confirmed MB destruction by inertial cavitation. MB-facilitated US ablation in an ex vivo perfused myocardium model generated shallow (2 mm) lesions and, in an in vivo murine hindlimb model, reduced perfusion by 42% with perivascular hemorrhage and inflammation, but no myonecrosis.

Consistent opening of the blood brain barrier using focused ultrasound with constant intravenous infusion of microbubble agent.

The blood brain barrier (BBB) is a major obstacle to the delivery of therapeutics to the brain. Focused ultrasound (FUS) in combination with microbubbles can non-invasively open the BBB in a targeted manner. Bolus intravenous injections of microbubbles are standard practice, but dynamic influx and clearance mechanisms prevent delivery of a uniform dose with time. When multiple targets are selected for sonication in a single treatment, uniform serum concentrations of microbubbles are important for consistent BBB opening. Herein, we show that bubble infusions were able to achieve consistent BBB opening at multiple target sites. FUS exposures were conducted with different Definity microbubble concentrations at various acoustic pressures. To quantify the effects of infusion on BBB opening, we calculated the MRI contrast enhancement rate. When infusions were performed at rates of 7.2 µl microbubbles/kg/min or below, we were able to obtain consistent BBB opening without injury at all pressures. However, when infusion rates exceeded 20 µl/kg/min, signs of injury occurred at pressures from 0.39 to 0.56 MPa. When compared to bolus injections, a bubble infusion offers a more controlled and consistent approach to multi-target BBB disruption.

Molecular Ultrasound Imaging.

Contrast-enhanced ultrasound (CEUS) imaging is a valuable tool for preclinical and clinical diagnostics. The most frequently used ultrasound contrast agents are microbubbles. Besides them, novel nano-sized materials are under investigation, which are briefly discussed in this chapter. For molecular CEUS, the ultrasound contrast agents are modified to actively target disease-associated molecular markers with a site-specific ligand. The most common markers for tumor imaging are related to neoangiogenesis, like the vascular endothelial growth factor receptor-2 (VEGFR2) and αvß3 integrin. In this chapter, applications of molecular ultrasound to longitudinally monitor receptor expression during tumor growth, to detect neovascularization, and to evaluate therapy responses are described. Furthermore, we report on first clinical trials of molecular CEUS with VEGFR2-targeted phospholipid microbubbles showing promising results regarding patient safety and its ability to detect tumors of prostate, breast, and ovary. The chapter closes with an outlook on ultrasound theranostics, where (targeted) ultrasound contrast agents are used to increase the permeability of tumor tissues and to support drug delivery.

High-Resolution Imaging of Intracellular Calcium Fluctuations Caused by Oscillating Microbubbles.

Ultrasound insonification of microbubbles can locally enhance drug delivery, but the microbubble-cell interaction remains poorly understood. Because intracellular calcium (Cai2+) is a key cellular regulator, unraveling the Cai2+ fluctuations caused by an oscillating microbubble provides crucial insight into the underlying bio-effects. Therefore, we developed an optical imaging system at nanometer and nanosecond resolution that can resolve Cai2+ fluctuations and microbubble oscillations. Using this system, we clearly distinguished three Cai2+ uptake profiles upon sonoporation of endothelial cells, which strongly correlated with the microbubble oscillation amplitude, severity of sonoporation and opening of cell-cell contacts. We found a narrow operating range for viable drug delivery without lethal cell damage. Moreover, adjacent cells were affected by a calcium wave propagating at 15 µm/s. With the unique optical system, we unraveled the microbubble oscillation behavior required for drug delivery and Cai2+ fluctuations, providing new insight into the microbubble-cell interaction to aid clinical translation.

Observed Effects of Whole-Brain Radiation Therapy on Focused Ultrasound Blood-Brain Barrier Disruption.

As focused ultrasound for blood-brain barrier disruption (FUS-BBBD) has progressed to human application, it has become necessary to consider the potential effects of prior irradiation treatments. Using a murine model, we examined the effects of whole-brain irradiation on FUS-BBBD. We first subjected half of the experimental cohort to daily 3-Gy whole-brain irradiation for 10 consecutive days. Then, microbubble-assisted FUS-BBBD was performed unilaterally while the contralateral sides served as unsonicated controls. FUS-BBBD, as evident by measuring the fluorescence yield of extravasated trypan blue dye, was identified at all sites with minimal or no apparent pathology. The peak fluorescence intensity caused by extravasated dye in the sonicated region was 17.5 ± 12.1% higher after radiation and FUS-BBBD than after FUS-BBBD alone, suggesting that prior radiation of the brain may be a sensitizing factor for FUS-BBBD. Radiation alone-without FUS-BBBD-resulted in mild BBB disruption. Hemorrhagic petechiae were observed in 9 of 12 radiated brains, with 77% of them clearly located outside the sonicated area; no petechiae were found in non-irradiated animals. This radiation protocol did not appear to increase the risk for vascular damage associated with FUS-BBBD.

Investigating the effects of dexamethasone on blood-brain barrier permeability and inflammatory response following focused ultrasound and microbubble exposure.

Rationale: Clinical trials are currently underway to test the safety and efficacy of delivering therapeutic agents across the blood-brain barrier (BBB) using focused ultrasound and microbubbles (FUS+MBs). While acoustic feedback control strategies have largely minimized the risk of overt tissue damage, transient induction of inflammatory processes have been observed following sonication in preclinical studies. The goal of this work was to explore the potential of post-sonication dexamethasone (DEX) administration as a means to mitigate treatment risk. Vascular permeability, inflammatory protein expression, blood vessel growth, and astrocyte activation were assessed. Methods: A single-element focused transducer (transmit frequency = 580 kHz) and DefinityTM microbubbles were used to increase BBB permeability unilaterally in the dorsal hippocampi of adult male rats. Sonicating pressure was calibrated based on ultraharmonic emissions. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) was used to quantitatively assess BBB permeability at 15 min (baseline) and 2 hrs following sonication. DEX was administered following baseline imaging and at 24 hrs post-FUS+MB exposure. Expression of key inflammatory proteins were assessed at 2 days, and astrocyte activation and blood vessel growth were assessed at 10 days post-FUS+MB exposure. Results: Compared to saline-treated control animals, DEX administration expedited the restoration of BBB integrity at 2 hrs, and significantly limited the production of key inflammation-related proteins at 2 days, following sonication. Indications of FUS+MB-induced astrocyte activation and vascular growth were diminished at 10 days in DEX-treated animals, compared to controls. Conclusions: These results suggest that DEX provides a means of modulating the duration of BBB permeability enhancement and may reduce the risk of inflammation-induced tissue damage, increasing the safety profile of this drug-delivery strategy. This effect may be especially relevant in scenarios for which the goal of treatment is to restore or preserve neural function and multiple sonications are required.

Cardiac-Neurovascular Adverse Effects Responsible to Contrast Transcranial Doppler: A Case Report.

Introduction and Case Presentation: A 44-year-old female patient suffered migraines and underwent contrast-enhanced transcranial Doppler (c-TCD). During the rapid injection of contrast agent, she suffered chest tightness, palpitation, decreased consciousness, perimouth numbness, and headache, respectively. Meanwhile, "curtain" pattern of air embolic signals lasted up to 115 seconds in her decreased right middle cerebral artery accompanied with arrhythmia. The microair embolic signals lasted as long as 340 seconds. The patient's symptoms were relieved in 30 minutes. The aforementioned symptoms and signs occurred, lasted, then disappeared coinciding in time with changes of microbubbles. The woman was later found to have ventricular septal defect. Discussion: The adverse effects to cardiac-neurovascular system of c-TCD are reported for the first time, which arouse attention to safety of the procedure.

Scale-up production, characterization and toxicity of a freeze-dried lipid-stabilized microbubble formulation for ultrasound imaging and therapy.

Microbubble formulations have a long history for enhancement of ultrasound (US) imaging and recently also for therapeutic applications. Previously, a series of freeze-dried bubble formulations based on the lipids DSPC and DSPG were developed. Here, we have attempted to scale-up the production process for future more extensive studies. Bubbles were prepared by homogenization of a lipid dispersion in a perfluoropropane atmosphere in a medium size (300-500 mL) homogenizer and then freeze-dried for better storage stability. In total, 300 freeze-dried vials were prepared. The properties of the bubbles were similar to those previously prepared on a lab scale with the difference that they were slightly larger and also had a better stability. The re-entrapped gas concentration after re-constituted freeze-dried bubbles was 9.4 µL/µmol lipid. The re-entrapped rate was 72.3% of fresh bubble before freeze-drying (13.0 µL/µmol lipid). The half-life of US imaging signal of the re-constituted freeze-dried bubbles in water in vitro was shorter than that of the fresh bubbles (2.7 min vs. 3.3 min). A leak of Evans Blue, that binds to albumin, from mouse ear blood vessel was observed after combination of bubble and US irradiation of 1 MHz for 1 min. As a result of bubble vibration by US irradiation, vascular endothelial cell bond opened and Evans Blue leaked. Toxicity of bubble was tested in rats. No toxicity was found after a single injection in the dose range tested. No serious toxicity was seen after repeated injections (one daily injection during 15 days).

Precision pulse capsulotomy complicated by radial tear of the anterior capsule: a proposed mechanism.

Zepto precision pulsed capsulotomy is an emerging technology aimed at providing a safer and more reproducible anterior capsulorhexis, with potential advantages in challenging cases. Initial reports suggest high safety, and thus far to our knowledge, no complications have been reported. Herein we report an unexpected complication. After the pulse delivery phase on a routine cataract case, a radial tear of the anterior capsule was observed. Upon careful review of the surgery video, an air bubble was noted, at the precise clock hour of the radial tear, trapped between the device wire and capsule. This air bubble presumably prevented the transfer of rapid phase transition at this site, interfering with capsule cleavage, and resulting in incomplete capsulotomy. Based on this observation, if a trapped air bubble is observed after the vacuum phase, we recommend applying more vacuum or disengaging and reattaching, before proceeding to the pulse delivery stage.

Improved delivery of doxorubicin by altering the tumor microenvironment using ultrasound combined with microbubbles and chemotherapy.

PURPOSE: To determine whether low-intensity pulsed ultrasound (US) using microbubbles (MB) can temporarily promote regional blood flow in the tumor and increase the delivery of doxorubicin (ad). METHODS: We randomly divided 66 tumor-bearing rabbits into 6 groups (n=11/group). The 6 groups were as follows: doxorubicin and ultrasound combined with microbubble treatment group (Ad-US-MB treatment group), US-MB treatment group, US treatment group, MB treatment group, doxorubicin treatment group (Ad-treatment group), and control group. The animals were intravenously injected with doxorubicin hydrochloride; next, the tumors in the Ad-US-MB treatment group were subjected to low-intensity ultrasound with microbubbles for 10 min. Contrast-enhanced ultrasound (CEUS) imaging of tumor tissues was performed before and after the intervention. Next, we randomly selected 8 rabbits/group, which were euthanized immediately after treatment. The remaining rabbits were reared and underwent the intervention every 7 days. RESULTS: Tumor perfusion increased immediately in the Ad-US-MB treatment group (p<0.01). Unlike the Ad treatment group, the Ad-US-MB treatment group showed high levels of doxorubicin in the tumor samples (p<0.05). Immunofluorescent staining showed high levels of doxorubicin mainly around the blood vessels; in addition, doxorubicin was observed in other areas in the Ad-US-MB treatment group. Inhibition of tumor growth was observed in the Ad-US-MB treatment group. CONCLUSIONS: Low-intensity ultrasound combined with microbubbles and chemotherapy can alter the tumor microenvironment and temporarily increase the regional blood flow to the tumor.

A combination of ultrasound-targeted microbubble destruction with transplantation of bone marrow mesenchymal stem cells promotes recovery of acute liver injury.

BACKGROUND: Bone marrow mesenchymal stem cells (BMSCs) can provide an additional source of therapeutic stem cells for regeneration of liver cells during acute liver injury (ALI). However, the insufficient hepatic homing by the transplanted BMSCs limits their applications. Ultrasound-targeted microbubble destruction (UTMD) has been reported to promote the homing of transplanted stem cells into the ischemic myocardium. In this study, we investigated whether UTMD promotes the hepatic homing of BMSCs in ALI rats and evaluated the therapeutic effect. METHODS: BMSCs were isolated from the femurs and tibias of Sprague-Dawley (SD) rats. The isolated BMSCs were stably transfected with a lentivirus expressing enhanced green fluorescent protein (EGFP) that can be visualized and quantified in vivo after transplantation. Both tumor necrosis factor α (TNF-α) and stromal cell-derived factor 1 (SDF-1) were used to verify the appropriate ultrasound parameters. The ALI rats were divided into four groups: control, BMSCs, UTMD, and UTMD + BMSCs. The protein and mRNA expression levels of SDF-1, intercellular cell adhesion molecule (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), hepatocyte growth factor (HGF), and monocyte chemotactic protein 1 (MCP-1) in the exposed livers were analyzed at 48 h after treatment. ALI recovery was determined by serum biochemical parameters and histology. RESULTS: The isolated rat BMSCs demonstrated a good proliferation potential that was both osteogenic and adipogenic in differentiation and expressed cluster of differentiation (CD) 29 and CD90, but not CD45 or CD11b/c. After BMSC and/or UTMD treatment, the number of GFP-labeled BMSCs in the UTMD + BMSCs group was significantly higher than that of the BMSCs group (9.8 ± 2.3 vs. 5.2 ± 1.1/per high-power field). Furthermore, the expression of GFP mRNA was performed for evaluation of the homing rate of BMSCs in injury sites as well. In addition, the expression levels of SDF-1, ICAM-1, VCAM-1, HGF, and MCP-1 were higher (p < 0.01) in UTMD+BMSCs group. The serum levels of biomarkers were significantly lower in the UTMD + BMSCs group, and the apoptotic rate of hepatocytes in the UTMD + BMSCs group was markedly lower than that of the BMSCs group (all p < 0.05). The hepatic pathology was significantly alleviated in the UTMD + BMSCs group. CONCLUSIONS: UTMD treatment efficiently induced a favorable microenvironment for cell engraftment, resulting in improvement of hepatic homing of BMSCs, which was probably mediated through upregulation of the expression of adhesion molecules and cytokines. UTMD treatment appeared to be an effective and noninvasive approach to achieve better efficacy of BMSC-based therapy for repairing a severely injured liver.

Frequency bands for ultrasound, suitable for the consideration of its health effects.

It is proposed that the ultrasound frequency spectrum should be divided into three bands in order to facilitate a more rational assessment of its health effects. Whilst statement of the frequencies at the borders of these bands facilitates their definition, it is recognized that these observables vary continuously with frequency and consequently these border frequencies should not be used to rule out the possibility of a given effect occurring. The lowest band, US(A), lies between 17.8 and 500 kHz. In this band acoustic cavitation and its associated forces form the dominant process resulting in biological effects in liquids and soft tissues, whereas health effects from airborne ultrasound have been reported but are far less researched. In the middle band, US(B), between 500 kHz and 100 MHz, temperature rise in tissues becomes the most important biological effect of exposure. The highest band, US(C), covers frequencies above 100 MHz, for which the radiation force becomes an increasingly important biophysical mechanism. A justification for the selection of 17.8 kHz in preference to any other threshold for the lower frequency limit for ultrasound is given.

MRI and histological evaluation of pulsed focused ultrasound and microbubbles treatment effects in the brain.

Magnetic resonance imaging (MRI)-guided pulsed focused ultrasound (pFUS) combined with microbubbles (MB) contrast agent infusion has been shown to transiently disrupt the blood-brain barrier (BBBD), increasing the delivery of neurotherapeutics to treat central nervous system (CNS) diseases. pFUS interaction with the intravascular MB results in acoustic cavitation forces passing through the neurovascular unit (NVU), inducing BBBD detected on contrast-enhanced MRI. Multiple pFUS+MB exposures in Alzheimer's disease (AD) models are being investigated as a method to clear amyloid plaques by activated microglia or infiltrating immune cells. Since it has been reported that pFUS+MB can induce a sterile inflammatory response (SIR) [1-5] in the rat, the goal of this study was to investigate the potential long-term effects of SIR in the brain following single and six weekly sonications by serial high-resolution MRI and pathology. Methods: Female Sprague Dawley rats weighing 217±16.6 g prior to sonication received bromo-deoxyuridine (BrdU) to tag proliferating cells in the brain. pFUS was performed at 548 kHz, ultrasound burst 10 ms and initial peak negative pressure of 0.3 MPa (in water) for 120 s coupled with a slow infusion of ~460 µL/kg (5-8×107 MB) that started 30 s before and 30 s during sonication. Nine 2 mm focal regions in the left cortex and four regions over the right hippocampus were treated with pFUS+MB. Serial high-resolution brain MRIs at 3 T and 9.4 T were obtained following a single or during the course of six weekly pFUS+MB resulting in BBBD in the left cortex and the right hippocampus. Animals were monitored over 7 to 13 weeks and imaging results were compared to histology. Results: Fewer than half of the rats receiving a single pFUS+MB exposure displayed hypointense voxels on T2*-weighted (w) MRI at week 7 or 13 in the cortex or hippocampus without differences compared to the contralateral side on histograms of T2* maps. Single sonicated rats had evidence of limited microglia activation on pathology compared to the contralateral hemisphere. Six weekly pFUS+MB treatments resulted in pathological changes on T2*w images with multiple hypointense regions, cortical atrophy, along with 50% of rats having persistent BBBD and astrogliosis by MRI. Pathologic analysis of the multiple sonicated animals demonstrated the presence of metallophagocytic Prussian blue-positive cells in the parenchyma with significantly (p<0.05) increased areas of activated astrocytes and microglia, and high numbers of systemic infiltrating CD68+ macrophages along with BrdU+ cells compared to contralateral brain. In addition, multiple treatments caused an increase in the number of hyperphosphorylated Tau (pTau)-positive neurons containing neurofibrillary tangles (NFT) in the sonicated cortex but not in the hippocampus when compared to contralateral brain, which was confirmed by Western blot (WB) (p<0.04). Conclusions: The repeated SIR following multiple pFUS+MB treatments could contribute to changes on MR imaging including persistent BBBD, cortical atrophy, and hypointense voxels on T2w and T2*w images consistent with pathological injury. Moreover, areas of astrogliosis, activated microglia, along with higher numbers of CD68+ infiltrating macrophages and BrdU+ cells were detected in multiple sonicated areas of the cortex and hippocampus. Elevations in pTau and NFT were detected in neurons of the multiple sonicated cortex. Minimal changes on MRI and histology were observed in single pFUS+MB-treated rats at 7 and 13 weeks post sonication. In comparison, animals that received 6 weekly sonications demonstrated evidence on MRI and histology of vascular damage, inflammation and neurodegeneration associated with the NVU commonly observed in trauma. Further investigation is recommended of the long-term effects of multiple pFUS+MB in clinical trials.

Stable cavitation using acoustic phase-change dodecafluoropentane nanoparticles for coronary micro-circulation thrombolysis.

BACKGROUND: The thrombolysis in micro-circulation after acute myocardial infarction has been an unsolved issue, as elimination effect of acute thrombolysis and primary intervention were unsatisfied. Stable cavitation using acoustic phase-change nanoparticles may have potential for thrombolysis. Therefore, we sought to investigate a novel treatment method with dodecafluoropentane (DDFP) nanoparticles for rapid and effective thrombolysis in an in-vitro artificial vascular system, as a mimicking preparation of coronary circulation. METHODS: To simulate thrombus embolism in coronary circulation, an in-vitro artificial vascular system was established with cavitation effect using DDFP nanoparticles. For PBS blank control (group A), SonoVue microbubbles (group B) and DDFP nanoparticles (group C), the durations for cavitation effect were recorded and the thrombolysis efficiency with low intensity focused ultrasound irradiation in the in-vitro vascular system were analyzed with weight loss and pathological changes of thrombus before and after thrombolysis. RESULTS: The optimal conditions for acoustic cavitation effect were power of 6 W for 20 min by ultrasound irradiation at 37 °C. The weight loss and weight loss rates of thrombus in group C (189.4 ±â€¯30.2 mg and 34.2 ±â€¯5.7%) were higher than those in group A (30.2 ±â€¯16.0 mg and 5.2 ±â€¯2.1%) and group B (84.0 ±â€¯20.4 mg and 14.6 ±â€¯1.5%) (P < 0.01, all). The duration for cavitation effect in group C (32.8 ±â€¯3.9 min) was also longer than those in group A (0.0 ±â€¯0.0 min) and group B (5.3 ±â€¯0.3 min) (P < 0.01, all). CONCLUSIONS: By stable and sustaining cavitation in targeted area, DDFP nanoparticles with ultrasound irradiation have significantly increased the thrombolysis efficiency, which has provided a powerful experimental foundation for potential coronary thrombolysis.

Inside/outside the brain binary cavitation localization based on the lowpass filter effect of the skull on the harmonic content: a proof of concept study.

Cavitation activity induced by ultrasound may occur during high intensity focused ultrasound (HIFU) treatment, due to bubble nucleation under high peak negative pressure, and during blood-brain-barrier (BBB) disruption, due to injected ultrasound contrast agents (UCAs). Such microbubble activity has to be monitored to assess the safety and efficiency of ultrasonic brain treatments. In this study, we aim at assessing whether cavitation occurs within cerebral tissue by binary discriminating cavitation activity originating from the inside or the outside of the skull. The results were obtained from both in vitro experiments mimicking BBB opening, by using UCA flow, and in vitro thermal necrosis in calf brain samples. The sonication was applied using a 1 MHz focused transducer and the acoustic response of the microbubbles was recorded with a wideband passive cavitation detector. The spectral content of the recorded signal was used to localize microbubble activity. Since the skull acts as a low pass filter, the ratio of high harmonics to low harmonics is lower for cavitation events located inside the skull compared to events outside the skull. Experiments showed that the ratio of the 5/2 ultraharmonic to the 1/2 subharmonic for binary localization cavitation activity achieves 100% sensitivity and specificity for both monkey and human skulls. The harmonic ratio of the fourth to the second harmonic provided 100% sensitivity and 96% and 46% specificity on a non-human primate for thermal necrosis and BBB opening, respectively. Nonetheless, the harmonic ratio remains promising for human applications, as the experiments showed 100% sensitivity and 100% specificity for both thermal necrosis and BBB opening through the human skull. The study requires further validation on a larger number of skull samples.