A Study on the Contributions of Sonication to the Identification of Bacteria Associated with Intubation Cannula Biofilm and the Risk of Ventilator-Associated Pneumonia.

Ventilator-associated pneumonia is one of the most severe complications of critically ill patients that need mechanical respiratory support, as it poses a significant risk of prolonging hospitalization, disability, and even death. This is why physicians worldwide target newer methods for prevention, early diagnosis, and early target treatment for this condition. There are few methods for a quick etiological diagnosis of pneumonia, especially point of care, and most are only readily available in some intensive care units. This is why a new, simple, and cheap method is needed for determining the bacteria that might be infectious in a particular patient. The manner in question is sonication. Method: In this prospective, observational, single-center study, endotracheal cannula specimens will be collected from at least 100 patients in our intensive care unit. This specimen will be submitted to a specific sonication protocol for bacteria to dislodge the biofilm inside the cannula. The resulting liquid will be seeded on growth media, and then a comparison will be made between the germs in the biofilm and the ones in the tracheal secretion of the patient. The primary purpose is to determine the bacteria before the appearance of a manifest infection.

Cavitation with low-energy sonication during focused ultrasound thalamotomy for a patient with tremor-dominant Parkinson's disease: a potential risk.

We report a patient with tremor-dominant Parkinson's disease who had a mild cavitation bioeffect during magnetic resonance-guided focused ultrasound thalamotomy. During the aligning phase with low-energy sonication, cavitation caused mild dysarthria and paresthesia, prompting treatment cessation. At the same time, tremor and rigidity improved. MRI revealed extensive high-intensity lesions in the thalamus 1 day after the procedure followed by steroid infusion, which resulted in resolution of adverse events. Tremor and rigidity improved 1.5 years after the procedure. Although cavitation can relieve tremors and rigidity, it should be carefully monitored due to potential permanent adverse events by unpredictable and unknown behaviors.

High intensity focused ultrasound combined with ultrasound-guided suction curettage treatment for cesarean scar pregnancy: a comparison of different HIFU sonication strategies.

OBJECTIVE: To explore a new high-intensity focused ultrasound (HIFU) sonication strategy for cesarean scar pregnancy (CSP) and to compare the clinical effectiveness and safety of this new HIFU sonication strategy with the conventional HIFU sonication strategy followed by ultrasound-guided dilation and curettage (USg-D&C) for CSP. MATERIALS AND METHODS: 91 patients with CSP treated by HIFU and USg-D&C in People's Hospital of Deyang City between January 2017 and December 2019 were retrospectively reviewed in this study. Based on the HIFU sonication strategy, patients were divided to two groups: 44 patients were exposed to 'C-shape' sonication layer by layer around the implantation location of the pregnancy sac (control group), while the other 47 patients were exposed to 'I-shape' sonication layer by layer only on the deep part which close to the bladder of the implantation location of the pregnancy sac (experimental group). The differences in clinical efficacy between the two groups were analyzed. Baseline characteristics, technical parameters of HIFU treatment and USg-D&C data were recorded. Adverse events were also recorded. RESULTS: No statistically significant difference was observed between the two groups in baseline characteristics including age, body mass index (BMI), menopause time, largest diameter of gestational sac, pretreatment serum ß-hCG, thickness of gestational sac, embedding myometrium, previous cesarean sections and interval from last cesarean section (CS). The average treatment intensity in the experimental group was significantly lower than that in the control group (p < .05). The median sonication time, total energy used for HIFU ablation, and energy efficiency factor (EEF) in the experimental group were significantly lower than the control group (p < .05). No statistically significant difference was observed between the two groups in treatment power and treatment time (p > .05). Sciatic/buttock pain and postoperative lower abdominal pain in the control group were significantly stronger than that in the experimental group (p < .05). There were no statistically significant differences in post-HIFU vaginal bleeding and discharging, urinary tract irritation, the operation time of USg-D&C, the amount of vaginal bleeding during USg-D&C, and the time for serum ß-hCG back to a normal level between the two groups (p > .05). CONCLUSIONS: The 'I-shape' strategy of HIFU treatment for CSP was effective and safe, with shorter sonication time, less energy input and lower incidence of sonication-related pain occurred in postoperative lower abdominal and sciatic nerve/buttock.

Evaluation of efficacy of new lens nucleus fragmenting forceps in cataract surgery / Avaliação da eficácia de uma nova pinça fragmentadora de núcleo do cristalino para cirurgia de catarata

ABSTRACT Objective: To evaluate the efficacy of low-cost nucleus fragmenting forceps designed to reduce the use of ultrasound during phacoemulsification. Methods: A total of 60 pig eyes enucleated 10 hours before were placed in the microwave oven, at maximum power for 10 seconds, to form cataracts with hardness comparable to a grade IV nucleus in the Lens Opacities Classification System III. Cataract extraction was performed using the Centurion® phacoemulsifier (Alcon Laboratories, Geneve, Switzerland) and Leica M620 microscope. All eyes were submitted to the pre-chop technique dividing the nucleus into four parts. After the pre-chop, the quadrants in 30 eyes were phacoemulsified with the torsional mode and were fragmented in the remaining 30 eyes after the pre-chop was with the fragmentation forceps before torsional mode phacoemulsification. The device was calibrated for all eyes by applying the following parameters: 40% linear torsional phacoemulsification; intraocular pressure of 65 mmHg; the linear vacuum of 600 mmHg; aspiration flow of 40 ccs/minute. After each procedure, the following was recorded: cumulative dissipated energy; equivalent average torsional amplitude; equivalent average ultrasonic power; estimated aspirated fluid; ultrasound total time; and total aspiration time. Statistical analysis was performed using the Kruskal-Wallis test and the IBM Statistical Package for Social Sciences. The p-value <0.05 was considered statistically significant. Results: There was a statistically significant reduction favoring the use of the nucleus fragmenting forceps in all parameters, except for the average torsional amplitude. Conclusion: The use of the nucleus fragmenting forceps contributed to improving the efficacy of torsional phacoemulsification in enucleated pig eyes.

RESUMO Objetivo: Avaliar a eficácia de uma pinça fragmentadora de núcleo, de baixo custo, desenvolvida para reduzir o uso de ultrassom durante a emulsificação do núcleo. Métodos: Sessenta olhos de porco com 10 horas de enucleação foram colocados no forno de microondas, em potência máxima por 10 segundos, para a formação de catarata com dureza comparável à de um núcleo grau IV na Lens Opacities Classification System III. A extração da catarata foi realizada com o facoemulsificador Centurion® (Alcon Laboratories, Genebra, Suíça) e microscópio Leica M620. Todos os olhos foram submetidos a técnica de pre-chop, dividindo o núcleo em quatro partes. Em 30 olhos, após o pre-chop, foi feita a facoemulsificação dos quadrantes com o modo torsional e, nos outros 30 olhos, após o pre-chop, cada quadrante foi fragmentado com a pinça antes da facoemulsificação com o modo torsional. O aparelho foi calibrado para todos os olhos com os seguintes parâmetros: faco torsional linear 40%; pressão intraocular 65 mmHg; vácuo linear 600mmHg e fluxo de aspiração 40cc/minuto. Após cada procedimento, verificaram-se energia dissipada acumulada; média da amplitude do faco torsional; média equivalente do poder ultrassônico; líquido aspirado estimado; tempo total de ultrassom e tempo total de aspiração. A análise estatística foi realizada utilizando o teste de Kruskal-Wallis com o IBM Statistical Package for Social Sciences. Valor de p<0,05 foi considerado estatisticamente significante. Resultados: Houve redução estatisticamente significante em favor do uso da pinça fragmentadora de núcleo em todos os parâmetros, menos na média de amplitude do faco torsional. Conclusão: O uso da pinça fragmentadora de núcleo contribuiu para melhorar a eficácia do faco torsional em olhos de porco enucleados.

Cavitation-modulated inflammatory response following focused ultrasound blood-brain barrier opening.

Focused ultrasound (FUS) in combination with systemically injected microbubbles can be used to non-invasively open the blood-brain barrier (BBB) in targeted regions for a variety of therapeutic applications. Over the past two decades, preclinical research into the safety and efficacy of FUS-induced BBB opening has proven this technique to be transient and efficacious, propelling FUS-induced BBB opening into several clinical trials in recent years. However, as clinical trials further progress, the neuroinflammatory response to FUS-induced BBB opening needs to be better understood. In this study, we provide further insight into the relationship of microbubble cavitation and the resulting innate immune response to FUS-induced BBB opening. By keeping ultrasound parameters fixed (i.e. frequency, pressure, pulse length, etc.), three groups of mice were sonicated using a real-time cavitation controller until a target cavitation dose was reached (1 x 107 V2•s, 5 x 107 V2•s, 1 x 108 V2•s). The change in relative gene expression of the mouse inflammatory cytokines and receptors were evaluated at three different time-points (6 h, 24 h, and 72 h) after FUS. At both 6 and 24 h time-points, significant changes in relative gene expression of inflammatory cytokines and receptors were observed across all cavitation groups. However, the degree of changes in relative expression levels and the number of genes with significant changes in expression varied across the cavitation groups. Groups with a higher cavitation dose exhibited both greater changes in relative expression levels and greater number of significant changes. By 72 h post-opening, the gene expression levels returned to baseline in all cavitation dose groups, signifying a transient inflammatory response to FUS-induced BBB opening at the targeted cavitation dose levels. Furthermore, the real-time cavitation controller was able to produce consistent and significantly different BBB permeability enhancement volumes across the three different cavitation dose groups. These results indicate that cavitation monitoring and controlling during FUS-induced BBB opening can be used to potentially modulate or limit the degree of neuroinflammation, further emphasizing the importance of implementing cavitation controllers as FUS-induced BBB opening is translated into the clinic.

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.

Blood-brain barrier disruption and delivery of irinotecan in a rat model using a clinical transcranial MRI-guided focused ultrasound system.

We investigated controlled blood-brain barrier (BBB) disruption using a low-frequency clinical transcranial MRI-guided focused ultrasound (TcMRgFUS) device and evaluated enhanced delivery of irinotecan chemotherapy to the brain and a rat glioma model. Animals received three weekly sessions of FUS, FUS and 10 mg/kg irinotecan, or irinotecan alone. In each session, four volumetric sonications targeted 36 locations in one hemisphere. With feedback control based on recordings of acoustic emissions, 98% of the sonication targets (1045/1071) reached a pre-defined level of acoustic emission, while the probability of wideband emission (a signature for inertial cavitation) was than 1%. BBB disruption, evaluated by mapping the R1 relaxation rate after administration of an MRI contrast agent, was significantly higher in the sonicated hemisphere (P < 0.01). Histological evaluation found minimal tissue effects. Irinotecan concentrations in the brain were significantly higher (P < 0.001) with BBB disruption, but SN-38 was only detected in <50% of the samples and only with an excessive irinotecan dose. Irinotecan with BBB disruption did not impede tumor growth or increase survival. Overall these results demonstrate safe and controlled BBB disruption with a low-frequency clinical TcMRgFUS device. While irinotecan delivery to the brain was not neurotoxic, it did not improve outcomes in the F98 glioma model.

Focused ultrasound as a novel strategy for noninvasive gene delivery to retinal Müller glia.

Müller glia are specialized retinal cells with stem cell properties in fish and frogs but not in mammals. Current efforts to develop gene therapies to activate mammalian Müller glia for retinal repair will require safe and effective delivery strategies for recombinant adeno-associated viruses (AAVs), vectors of choice for clinical translation. Intravitreal and subretinal injections are currently used for AAV gene delivery in the eye, but less invasive methods efficiently targeting Müller glia have yet to be developed. Methods: As gene delivery strategies have been more extensively studied in the brain, to validate our vectors, we initially compared the glial tropism of AAV-PHP.eB, an AAV9 that crosses the blood-brain and blood-retinal barriers, for its ability to drive fluorescent protein expression in glial cells in both the brain and retina. We then tested the glial transduction of AAV2/8-GFAP-mCherry, a virus that does not cross blood-brain and blood-retinal barriers, for its effectiveness in transducing Müller glia in murine retinal explants ex vivo. For in vivo assays we used larger rat eyes, performing invasive intravitreal injections, and non-invasive intravenous delivery using focused ultrasound (FUS) (pressure amplitude: 0.360 - 0.84 MPa) and microbubbles (Definity, 0.2 ml/kg). Results: We showed that AAV-PHP.eB carrying a ubiquitous promoter (CAG) and green fluorescent protein (GFP) reporter, readily crossed the blood-brain and blood-retinal barriers after intravenous delivery in mice. However, murine Müller glia did not express GFP, suggesting that they were not transduced by AAV-PHP.eB. We thus tested an AAV2/8 variant, which was selected based on its safety record in multiple clinical trials, adding a glial fibrillary acidic protein (GFAP) promoter and mCherry (red fluorescent protein) reporter. We confirmed the glial specificity of AAV2/8-GFAP-mCherry, showing effective expression of mCherry in astrocytes after intracranial injection in the mouse brain, and of Müller glia in murine retinal explants. For in vivo experiments we switched to rats because of their larger size, injecting AAV2/8-GFAP-mCherry intravitreally, an invasive procedure, demonstrating passage across the inner limiting membrane, leading to Müller glia transduction. We then tested an alternative non-invasive delivery approach targeting a different barrier - the inner blood-retinal-barrier, applying focused ultrasound (FUS) to the retina after intravenous injection of AAV2/8 and microbubbles in rats, using magnetic resonance imaging (MRI) for FUS targeting. FUS permeabilized the rat blood-retinal-barrier and allowed the passage of macromolecules to the retina (Evans blue, IgG, IgM), with minimal extravasation of platelets and red blood cells. Intravenous injection of microbubbles and AAV2/8-GFAP-mCherry followed by FUS resulted in mCherry expression in rat Müller glia. However, systemic delivery of AAV2/8 also had off-target effects, transducing several murine peripheral organs, particularly the liver. Conclusions: Retinal permeabilisation via FUS in the presence of microbubbles is effective for delivering AAV2/8 across the inner blood-retinal-barrier, targeting Müller glia, which is less invasive than intravitreal injections that bypass the inner limiting membrane. However, implementing FUS in the clinic will require a comprehensive consideration of any off-target tropism of the AAV in peripheral organs, combined ideally, with the development of Müller glia-specific promoters.

Avaliação do método diagnóstico vórtex e sonicação nas infecções de corrente sanguínea relacionadas à cateteres em pacientes portadores do vírus da imunodeficiência humana / Evaluation of the method vortex and sonication in the diagnosis of central line associated bloodstream infection among people with human immunodeficiency virus

Introdução: O uso do cateter venoso central (CVC) é comum no ambiente hospitalar, porém está associado à formação de biofilmes, levando a infecção primária de corrente sanguínea associada à cateter (IPCS). Os métodos diagnósticos atualmente recomendados para infecção primária de corrente sanguínea relacionada a cateter (ICSRC) são rolamento, sonicação e hemocultura. A sensibilidade e especificidade de tais métodos foram testados na população geral, entretanto não sabemos qual o comportamento na população vivendo com vírus da imunodeficiência humana (PVHIV). De tal forma, avaliamos os métodos vórtex -sonicação-vórtex e o comparamos com rolamento e hemocultura. Objetivo: comparar acurácia dos métodos rolamento do cateter, vórtex-sonicação-vórtex e hemoculturas em frascos, para o diagnóstico de infecção de corrente sanguínea relacionado à cateter (ICSRC), na PVHIV adulta no Instituto de Infectologia Emilio Ribas (IIER). Metodologia: Estudo piloto para comparação da acurácia de métodos diagnósticos de ICSRC na PVHIV nos meses de outubro e novembro de 2019, de acordo com os critérios da ANVISA, 2017. Resultados: Avaliamos 10 cateteres pertencentes a 9 pacientes. Das 10 amostras foram isolados os seguintes agentes: CoNs, E.coli, E.faecium, E.faecalis, K.pneumoniae, A.lwoffii e A.haemolyticus, porém nem todas preenchiam critério de definição para ICSRC. O diagnóstico pelo método vórtex-sonicação-vórtex, assim como o rolamento, não se fez presente em nenhum dos casos, apesar de microorganismos terem sido isolados por esses métodos, pois não preencheram os critérios preconizados pela ANVISA. Duas amostras (20%) alcançaram o critério para ICSRC e as outras oito (80%) somente suspeita de IPCS. A acurácia do rolamento e hemocultura, quando comparada a sonicação, foi de 0,8 e 1,0 respectivamente. Os agentes responsáveis por ICSRC no nosso trabalho foram: Acinetobacter lwoffii e Acinetobacter haemolyticus. Não foi possível realizar análise de associação devido ao pequeno número de cateteres no estudo piloto. Conclusão: Observamos em nosso estudo piloto que o método vórtex-sonicação-vórtex isolou mais microorganismos, do que o rolamento, porém por nenhum dos dois métodos foi possível preencher o critério de ICSRC na população portadora do vírus da imunodeficiência humana. O critério inclui o isolamento do agente por um desses métodos, respeitando o cut-off de cada um, associado a hemocultura com isolamento do mesmo agente. São necessários mais estudos com número 6 maior de participantes para avaliação da acurácia dos métodos, bem como a definição do cut-off para essa população para melhor sensibilidade e especificidade dos métodos diagnósticos

Effects of sonication parameters on transcranial focused ultrasound brain stimulation in an ovine model.

Low-intensity focused ultrasound (FUS) has significant potential as a non-invasive brain stimulation modality and novel technique for functional brain mapping, particularly with its advantage of greater spatial selectivity and depth penetration compared to existing non-invasive brain stimulation techniques. As previous studies, primarily carried out in small animals, have demonstrated that sonication parameters affect the stimulation efficiency, further investigation in large animals is necessary to translate this technique into clinical practice. In the present study, we examined the effects of sonication parameters on the transient modification of excitability of cortical and thalamic areas in an ovine model. Guided by anatomical and functional neuroimaging data specific to each animal, 250 kHz FUS was transcranially applied to the primary sensorimotor area associated with the right hind limb and its thalamic projection in sheep (n = 10) across multiple sessions using various combinations of sonication parameters. The degree of effect from FUS was assessed through electrophysiological responses, through analysis of electromyogram and electroencephalographic somatosensory evoked potentials for evaluation of excitatory and suppressive effects, respectively. We found that the modulatory effects were transient and reversible, with specific sonication parameters outperforming others in modulating regional brain activity. Magnetic resonance imaging and histological analysis conducted at different time points after the final sonication session, as well as behavioral observations, showed that repeated exposure to FUS did not damage the underlying brain tissue. Our results suggest that FUS-mediated, non-invasive, region-specific bimodal neuromodulation can be safely achieved in an ovine model, indicating its potential for translation into human studies.

Preserving the Efficacy of Glycopeptide Antibiotics during Nanoencapsulation in Liposomes.

Liposome nanovesicles are attractive vehicles for encapsulation and localized delivery of antibiotics. Most liposomal batch preparation processes involve numerous freeze-thaw cycles and heating or sonication steps, all of which can potentially deactivate or degrade antibiotics. We investigated the extent of antibiotic deactivation during various liposomal preparation methods using two glycopeptide antibiotics clinically administered for Staphylococcus infections, namely, vancomycin hydrochloride and teicoplanin. Both antibiotics, in the nonencapsulated state, were found to be highly sensitive to the freeze-thaw/sonication; vancomycin completely lost efficacy after only three cycles of freeze-thaw, and teicoplanin lost efficacy after 20 min of sonication. When the antibiotics were encapsulated in liposomes, vancomycin retained full potency against bacterial cultures of Staphylococcus aureus but encapsulated teicoplanin suffered a decrease in activity. Differential scanning calorimetry and mass spectrometry suggest that liposomes have a protective effect on the encapsulated antibiotic, the extent of which was found to differ on the basis of the processing conditions.

Unexpected positive cultures in presumed aseptic revision spine surgery using sonication.

AIMS: During revision procedures for aseptic reasons, there remains a suspicion that failure may have been the result of an undetected subclinical infection. However, there is little evidence available in the literature about unexpected positive results in presumed aseptic revision spine surgery. The aims of our study were to estimate the prevalence of unexpected positive culture using sonication and to evaluate clinical characteristics of these patients. PATIENTS AND METHODS: All patients who underwent a revision surgery after instrumented spinal surgery at our institution between July 2014 and August 2016 with spinal implants submitted for sonication were retrospectively analyzed. Only revisions presumed as aseptic are included in the study. During the study period, 204 spinal revisions were performed for diagnoses other than infection. In 38 cases, sonication cultures were not obtained, leaving a study cohort of 166 cases. The mean age of the cohort was 61.5 years (sd 20.4) and there were 104 female patients. RESULTS: Sonication cultures were positive in 75 cases (45.2%). Hardware failure was the most common indication for revision surgery and revealed a positive sonication culture in 26/75 cases (35%) followed by adjacent segment disease (ASD) in 23/75 cases (30%). Cutibacterium acnes and Staphylococcus epidermidis were the most commonly isolated microorganisms, observed in 45% and 31% of cases, respectively. C. acnes was isolated in 65.2% of cases when the indication for revision surgery was ASD. CONCLUSION: Infection must always be considered as a possibility in the setting of spinal revision surgery, especially in the case of hardware failure, regardless of the lack of clinical signs. Sonication should be routinely used to isolate microorganisms adherent to implants. Cite this article: Bone Joint J 2019;101-B:621-624.

High frequency of low-virulent microorganisms detected by sonication of pedicle screws: a potential cause for implant failure.

OBJECTIVE: Loosening of pedicle screws is a frequent complication after spinal surgery. Implant colonization with low-virulent microorganisms forming biofilms may cause implant loosening. However, the clinical evidence of this mechanism is lacking. Here, the authors evaluated the potential role of microbial colonization using sonication in patients with clinical pedicle screw loosening but without signs of infection. METHODS: All consecutive patients undergoing hardware removal between January 2015 and December 2017, including patients with screw loosening but without clinical signs of infection, were evaluated. The removed hardware was investigated using sonication. RESULTS: A total of 82 patients with a mean (± SD) patient age of 65 ± 13 years were eligible for evaluation. Of the 54 patients with screw loosening, 22 patients (40.7%) had a positive sonication result. None of the 28 patients without screw loosening who served as a control cohort showed a positive sonication result (p < 0.01). In total, 24 microorganisms were detected in those 22 patients. The most common isolated microorganisms were coagulase-negative staphylococci (62.5%) and Cutibacterium acnes (formerly known as Propionibacterium acnes) (25%). When comparing only the patients with screw loosening, the duration of the previous spine surgery was significantly longer in patients with a positive microbiological result (288 ± 147 minutes) than in those with a negative result (201 ± 103 minutes) (p = 0.02). CONCLUSIONS: The low-virulent microorganisms frequently detected on pedicle screws by using sonication may be an important cause of implant loosening and failure. Longer surgical duration increases the likelihood of implant colonization with subsequent screw loosening. Sonication is a highly sensitive approach to detect biofilm-producing bacteria, and it needs to be integrated into the clinical routine for optimized treatment strategies.

Time-domain simulation of ultrasound propagation with fractional Laplacians for lossy-medium biological tissues with complicated geometries.

Simulations of ultrasound wave propagation inside biological tissues have a wide range of practical applications. In previous studies, wave propagation equations in lossy biological media are solved either with convolutions, which consume a large amount of memory, or with pseudo-spectral methods, which cannot handle complicated geometries effectively. The approach described in the paper employed a fractional central difference method (FCD), combined with the immersed boundary (IB) method for the finite-difference, time-domain simulation. The FCD method can solve the fractional Laplace terms in Chen and Holm's lossy-medium equations directly in the physical domain without integral transforms. It also works naturally with the IB method, which enables a simple Cartesian-type grid mesh to be used to solve problems with complicated geometries. The numerical results agree very well with the analytical solutions for frequency power-law attenuation lossy media.

Evaluation of Crack Formation and Propagation with Ultrasonic Root-End Preparation and Obturation Using a Digital Microscope and Optical Coherence Tomography.

OBJECTIVE: This study is aimed at determining (1) the effect of root-end resection, ultrasonic root-end preparation, and root-end filling on the incidence of crack formation and propagation by using a digital microscope (DM) and optical coherence tomography (OCT) and (2) the performance of OCT on the detection of cracks by comparing with microcomputed tomography (micro-CT) as a reference standard. METHODOLOGY: Thirty extracted lower incisors were endodontically treated and subjected to root-end resection and ultrasonic root-end cavity preparation. Then, the teeth were divided into three groups (n = 10, each), and the root-end cavity was either left unfilled or filled with mineral trioxide aggregate (MTA) or super-EBA. The resected surface was observed with OCT and DM after the root-end resection, ultrasonic root-end preparation, and root-end filling, and the frequency of incomplete and complete cracks were recorded. The observation was repeated after two weeks, one month, and two months, and micro-CT scans after two months were taken as the gold standard. RESULTS: The DM results show dentinal crack formation in 47% of the samples following root-end resection and in 87% following ultrasonic preparation. After the ultrasonic preparation, no existing crack propagated to a complete crack, but new cracks were formed. MTA and super-EBA had no effect on crack formation. The Spearman correlation coefficient between OCT and DM was 0.186 (very weak correlation; p = 0.015). Sensitivity and specificity in comparison to micro-CT were 0.50 and 0.55 in OCT and 1.00 and 0.35 in DM, respectively. McNemar's test showed a significant difference between OCT and DM (p < 0.05). CONCLUSION: Apical resection and ultrasonic preparation could form dentinal cracks. OCT and DM showed different detection frequencies of cracks with very weak correlation. DM showed superior sensitivity compared with OCT.

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.

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.

Evaluation of viral contamination in a baculovirus expression system.

Insect expression systems based on baculovirus are widely used for generating recombinant proteins. Here, the infectivity of baculoviruses under the physiological stresses of 'freeze-thaw' and sonication and the baculoviral contamination of recombinant proteins after protein purification were evaluated. Our findings suggest that Nonidet P-40 (NP-40) treatment of baculoviruses completely abolishes their infectivity and that recombinant proteins purified with affinity beads do not include infectious baculoviruses. We therefore suggest that baculovirus is completely inactivated by NP-40 treatment and that recombinant proteins are unlikely to be contaminated with infectious baculoviruses after their affinity purification.

High-speed photographic observation of the sonication of a rabbit carotid artery filled with microbubbles by 20-kHz low frequency ultrasound.

The aim of this study is to assess the physical damage of cavitation effects induced by low frequency ultrasound and microbubbles (MBs) to an in vitro vessel. A rabbit carotid artery filled with SonoVue MBs and methylene blue was irradiated with 20-kHz ultrasound, and the results were recorded by high-speed photography at 3000 frames per second. The carotid artery filled with MBs experienced a slight tremor during ultrasonication. Six intermittent blue flow events occurred in two places on the artery wall during the 5-s process. The duration of each leakage event was 90-360ms with an average of 200ms. Hematoxylin-eosin (H-E) staining demonstrated the separation of the carotid artery elastic membrane, local blood vessel wall defects and hole formation, and the surface of the ruptured area was rough and irregular. Another carotid artery was filled with a 0.9% NaCl solution and methylene blue as a control and irradiated with 20-kHz ultrasound. No blue liquid flow was seen, and no holes in the vessel were observed. H-E staining revealed intact vascular endothelial cells and smooth muscles with no vascular wall defects. Low-frequency ultrasound combined with MBs can cause a vessel to rupture and holes to form in a short time. High-speed photography is useful for observing transient changes caused by the effects of ultrasound cavitation on an in vitro vessel.

Viability of endothelial cells after ultrasound-mediated sonoporation: Influence of targeting, oscillation, and displacement of microbubbles.

Microbubbles (MBs) have been shown to create transient or lethal pores in cell membranes under the influence of ultrasound, known as ultrasound-mediated sonoporation. Several studies have reported enhanced drug delivery or local cell death induced by MBs that are either targeted to a specific biomarker (targeted microbubbles, tMBs) or that are not targeted (non-targeted microbubbles, ntMBs). However, both the exact mechanism and the optimal acoustic settings for sonoporation are still unknown. In this study we used real-time uptake patterns of propidium iodide, a fluorescent cell impermeable model drug, as a measure for sonoporation. Combined with high-speed optical recordings of MB displacement and ultra-high-speed recordings of MB oscillation, we aimed to identify differences in MB behavior responsible for either viable sonoporation or cell death. We compared ntMBs and tMBs with identical shell compositions exposed to long acoustic pulses (500-50,000cycles) at various pressures (150-500kPa). Propidium iodide uptake highly correlated with cell viability; when the fluorescence intensity still increased 120s after opening of the pore, this resulted in cell death. Higher acoustic pressures and longer cycles resulted in more displacing MBs and enhanced sonoporation. Non-displacing MBs were found to be the main contributor to cell death, while displacement of tMBs enhanced reversible sonoporation and preserved cell viability. Consequently, each therapeutic application requires different settings: non-displacing ntMBs or tMBs are advantageous for therapies requiring cell death, especially at 500kPa and 50,000cycles, whereas short acoustic pulses causing limited displacement should be used for drug delivery.