Ultrasound Pulse Research Articles

Ultrasound pulse generation through continuous-wave laser excited thermo-cavitation for all-optical ultrasound imaging

The optical generation of pulsed ultrasound is attractive to nondestructive testing and biological imaging, especially for those involving narrow operation space or strong electro-magnetic interference. However, conventional techniques based on the photoacoustic effect inevitably required an expensive high-energy short pulsed laser and dedicated preparation of the optically absorptive composite film. Here, a fiber-optic ultrasound pulse transmitter based on continuous-wave (CW) laser triggered thermo-cavitation was demonstrated. The fiber-delivered CW laser light heated the highly-absorptive copper nitrate solution and generated explosive bubbles , which emitted strong ultrasound waves. Omnidirectional ultrasound pulses with an amplitude up to 0.3 MPa and a repetition rate of 5 kHz in the frequency range of 5–12 MHz were obtained by using a 50 mW optical heating power at a wavelength of 980 nm. The fiber-tip ultrasound transmitter was integrated with a polymer-cavity-based fiber ultrasound detector to construct an all-fiber ultrasound endoscopic imaging probe. Without the need for a wavelength-tunable laser, the ultrasound detector was interrogated by CW laser light with a fixed wavelength, coupled with feedback-controlled heating of the cavity to stabilize its spectral fringe. The CW laser-driven fiber ultrasound transmitter, in combination with the photothermally stabilized fiber ultrasound detector, opens new routes for a number of ultrasound-related industrial and biomedical applications.

Ultrasound sensitive O2 microbubbles radiosensitize murine breast cancer but lead to higher metastatic spread.

The inadequate level of oxygenation in tumors has been shown to correlate not only with greater invasiveness of cancer cells, but also with a reduction in their sensitivity to anticancer therapies. Over the years, many attempts have been made to increase the oxygenation level of cancer, but most of them have been ineffective. We investigated the heterogeneous response of tumor tissue to phospholipid-coated oxygen microbubbles (OMB) in murine tumors in vivo using oxygen and hemoglobin saturation mapping and the influence of OMB treatment on microvasculature, perfusion, and radiotherapy effectiveness. Intravenous administration of OMB followed by ultrasound pulse leads to increased oxygenation of a tumor, found mainly in the vicinity of tumor vessels, while intratumoral delivery resulted in areas of increased pO2 more evenly distributed within the tumor. Furthermore, hemoglobin contributes little to the increase in tumor oxygenation caused by oxygen microbubbles. Extensive vasculature disruption was observed in the groups treated with both oxygen/nitrogen microbubbles and ultrasound pulse. This therapy also led to a reduction in the coverage of the vessels by pericytes, while the density of the microvessels was unchanged. Radiotherapy with a single dose of 12Gy reduced tumor growth by 50% in all treated groups. Unfortunately, at the same time, the number of macroscopic metastases in the lungs increased significantly after intravenous administration of oxygen/nitrogen microbubbles and the application of an ultrasound pulse. In conclusion, ultrasound-sensitive oxygen microbubbles are effective in delivering oxygen to tumor tissue, thus increasing the effectiveness of radiotherapy. However, cavitation effects and destruction of the integrity of tumor vessels result in greater spread of cancer cells in the host organism.

Using Machine Learning to Classify Human Fetal Health and Analyze Feature Importance

The reduction of childhood mortality is an ongoing struggle and a commonly used factor in determining progress in the medical field. The under-5 mortality number is around 5 million around the world, with many of the deaths being preventable. In light of this issue, cardiotocograms (CTGs) have emerged as a leading tool to determine fetal health. By using ultrasound pulses and reading the responses, CTGs help healthcare professionals assess the overall health of the fetus to determine the risk of child mortality. However, interpreting the results of the CTGs is time consuming and inefficient, especially in underdeveloped areas where an expert obstetrician is hard to come by. Using a support vector machine (SVM) and oversampling, this paper proposes a model that classifies fetal health with an accuracy of 99.59%. To further explain the CTG measurements, an algorithm based off of RISE (Randomized Input Sampling for Explanation of Black-box Models) was created, called Feature Alteration for explanation of Black Box Models (FAB). The findings of this novel algorithm were compared to SHapley Additive exPlanations (SHAP) and Local Interpretable Model Agnostic Explanations (LIME). Overall, this technology allows doctors and medical professionals to classify fetal health with high accuracy and determine which features were most influential in the process.

The Fifth Bioelectronic Medicine Summit Hosted by the Feinstein Institutes for Medical Research (Manhasset, NY) and Columbia Engineering (NY, NY) at The Garden City Hotel, Garden City, NY 11530 on October 11-12th, 2022- Bioelectronic Medicine: Today’s Tools, Tomorrow’s Therapies

The Fifth Bioelectronic Medicine Summit Hosted by the Feinstein Institutes for Medical Research (Manhasset, NY) and Columbia Engineering (NY, NY) at The Garden City Hotel, Garden City, NY 11530 on October 11-12th, 2022- Bioelectronic Medicine: Today’s Tools, Tomorrow’s Therapies

Comparison of thermal effects induced by transcranial focused ultrasound and transcranial pulse stimulation

Abstract The objective of the study was to investigate thermal effects induced through two low-intensity focused ultrasound (LIFU)–based brain stimulation techniques—transcranial focused ultrasound stimulation (tFUS) and transcranial pulse stimulation (TPS). Long trains of acoustic pulses are delivered using tFUS, whereas, the newly introduced TPS delivers ultrashort (∼3 μs) pulses repeated at 4 Hz. It is presumed that TPS by virtue of delivering ultrashort ultrasound pulses reduces the risk for brain heating, but this has not been quantified in the literature. While overall temperature increase depends on the exact combination of stimulation parameters, simulations for tFUS have predicted ∼3°C and ∼<0.2 °C rises in a monkey skull and brain respectively. To our knowledge, the maximum rise ever reported is ∼3°C in rat brain but via a combination of longer duration and higher Ispta than typically used in tFUS. Following our previous work developing an image-derived model for TPS, we extended the models to assess transient heating in TPS as compared to tFUS. A finite difference time domain approach was used to solve the Westervelt-Lighthill equation for the pressure distribution in the head. Average intensity was calculated from the pressure distribution, which was then coupled to Pennes bioheat equation as a heat source. Initial results using certain assumptions indicate brain temperature rises in TPS to be <0.01°C. This indicates temperature rise at least an order of magnitude lower than some common tFUS parameters. While the absolute heating induced by either modality can be modulated by adjusting Ispta (through transducer intensity, duration, or duty cycle), typical tFUS and TPS protocols produce inherently different proportions of temperature versus pressure changes. In addition to risk, knowing the relative differences in temperature versus pressure generated could lend to a deeper understanding of the thermal versus mechanical mechanisms underlying the two techniques. Research Category and Technology and Methods Translational Research: 19. Modeling and computational methods Keywords: Ultrasound, tFUS, TPS, Thermal

Technological considerations for delivering focused ultrasound exposures to the spinal cord

Focused ultrasound opening of the blood-brain barrier (BBB) has reached clinical investigations and seems poised to revolutionize the treatment of brain disorders. Far less attention has been paid to the spinal cord and functionally equivalent blood-spinal cord barrier (BSCB). Small and large animal studies demonstrate that ultrasound and microbubbles can be used to modulate the BSCB in a similar manner to the BBB. However, the complex bony geometry of the vertebral column poses a challenge to the non-invasive delivery of therapeutic ultrasound exposures to the spinal canal. This talk will review work developing spine-specific ultrasound pulse trains and identifying optimal apertures for maximizing sound transmission through the vertebral arch.

Enhancing the Photocatalytic Activity of TiO2 for the Degradation of Congo Red Dye by Adjusting the Ultrasonication Regime Applied in Its Synthesis Procedure

Recently, the ultrasound-assisted sol-gel synthesis procedure of mesoporous titania (TiO2) photocatalysts caught the researcher’s attention, due to the physicochemical properties enhancement of the resulting titania nanomaterials. Thus, by varying different synthesis parameters particular characteristics could be obtained. In the present study, the ultrasound pulse on/off ratio has been considered and the effect of the envisaged parameter on the textural, morphological, and optical features of titania nanomaterial has been investigated. Therefore, X-ray Diffraction (XRD), Fourier-Transform Infrared spectroscopy (FTIR), N2-sorption measurements, SEM imaging, and UV-Vis Diffuse Reflectance spectroscopy (UVDR) have been used. And further, the photocatalytic activity of the prepared TiO2 materials was evaluated by the features developed about the applied ultrasound pulse on/off ratio as 1/1, 2/1, 3/1, 4/1, 1/3 and 2/2. It was found that the ultrasound pulse on/off ratio considered in the synthesis procedure of titania leads to TiO2 materials with different textural (SBET = 98–156 m2/g), morphological, and optical (Eg = 3.1–3.2 eV) characteristics. For this reason, TiO2 nanomaterials prepared were found to exhibit suitable features for photocatalytic applications. Thus, the TiO2 4.1 sample prepared at 4/1 ultrasound pulse on/off ratio revealed the highest photodegradation efficiency of Congo Red dye (98.28%) as the results of photocatalytic tests show. More than that, a possible reaction mechanism of the CR photodegradation process through the contribution of reactive oxygen species (·HO, ·O2−), holes (h+), and electrons (e−) of developed titania photocatalyst was proposed.

Wireless left ventricular endocardial left ventricular pacing (WiSE-CRT system)

We use CRT (Cardiac Resynchronization Therapy) to treat dyssynchrony and heart failure. However, 30-40% of patients do not respond to the current method. For these patients may solution be a new wireless endocardial CRT pacing. Power is supplied wirelessly via a subcutaneous ultrasound pulse generator. WiSE-CRT therapy offers many advantages, including the ability to provide local stimulation and targeted stimulation without regard to the implantation site in the left ventricle. Other benefits that were noted during treatment include QRS shorter duration, an increase in ejection fraction, and no need for treatment with anticoagulants. In addition, patients do not suffer from endocarditis associated with conventionally CRT. The efficacy of WiSE-CRT is tested, as it has already been positively evaluated in Europe.

Experimental assessment of mechanical and physical performance of latex modified concrete with fine recycled aggregate

One of the most crucial building materials is concrete. However, producing concrete consumes a significant amount of natural resources. Attention has been focused on using concrete debris and recycling it in the building industry to solve this issue. This study investigates latex-modified concrete's physical and mechanical performance when replacing fine natural aggregates (FNA) with different percentages of fine recycled aggregates (FRA). The study includes conducting laboratory tests to investigate the workability, slump loss, compaction factor, compressive strength, ultrasound pulse velocity, absorption, and porosity. When replacing fine natural aggregates (FNA) with different percentages of fine recycled aggregates (FRA), it was found that there is an inverse relationship between the slump, compressive strength, compaction factor, and the percentage of RFA. The existence of SBR latex in concrete to form polymer modified concrete led to a higher decrease in workability compared to unmodified concrete. The absorbability increases as the proportion of fine natural aggregates are replaced by recycled fine aggregates, possibly due to the higher porosity of recycled fine aggregates. The same conclusion can be generalized to the results of the porosity test. However, adding the polymer improves the absorption resistance and reduces the porosity when replacing the fine natural aggregate with the fine recycled aggregate. Additionally, the outcomes demonstrated that SBR latex compensates for the compressive strength loss caused by recycled fine aggregates.

Multifunctional silane-based superhydrophobic/impregnation treatments for concrete producing C-S-H gel: Validation on mockup specimens from European heritage structures

Many of the concrete structures that conform our modern cultural heritage are in need of repair and protective interventions. Silane-based impregnation treatments can be used to repair onset cracks and reinforce the surface due to their ability to produce silica and C-S-H gels, and can be modified by incorporating hydrophobic precursors to create multifunctional treatments that also protect from water ingress.Since the effectiveness of impregnation treatments is dependent on substrate properties and chemical-physical changes it may have experienced over time, validation using standard materials may not always be representative of on-site application. In this work, the effectiveness of three innovative silane-based impregnation treatments developed by our group (two of them combining superhydrophobic properties) was evaluated on mockup specimens, which simulate the properties of the cementitious materials from six different heritage structures across Europe, artificially aged to simulate weathering by three methods: carbonation, chloride ingress and physical damages (freeze–thaw and thermal cycles).The characterization of the treatments showed they are compatible in terms of chemical interaction, applicability and minimal aesthetical alterations. Surface resistance and ultrasound pulse measurements have been used to assess the improvement in mechanical properties. The incorporation of hydrophobic components and fumed silica has a relatively low impact over the mechanical properties while it significantly reduces water absorption and grants water repellent properties to the surface, giving rise to a superhydrophobic performance.

Optimized Local Synthetic Conditions Induce Size Reduction and Phase Purification in {[Fe(Htrz)2(trz)](BF4)}n Spin Crossover Particles

The well-known synthesis of the two polymorphs of the {[Fe(Htrz)2(trz)](BF4)}n spin crossover coordination polymer is explored with new template-free methods that allow a control over the local synthetic conditions. A “one-pot” synthesis approach is developed, in which the solid reactants are mixed together before the addition of the solvent, which is expected to generate instantaneous supersaturation conditions favoring the nucleation of particles over their growth. In a second method, the addition of ultrasound pulses promotes the appearance of local “hot spots” that affect the local temperature and allow exploring a different region of the concentration–temperature phase diagram, leading to an increase in the phase purity of the product. These two syntheses are compared to the classical method in which the reactants are first dissolved in separate solutions before being mixed. The use of a one-pot synthesis, with or without ultrasound pulses, induces a downsizing of the particle size by a factor of 500 on their volume. The addition of ultrasound pulses allows moving from a mixture of polymorphs I and II of this compound to the pure phase I. These approaches open the way to more studies on the control over the size or phase purity in such molecular compounds, without the use of any surfactant.

Ultrafast Background-Free Ultrasound Imaging Using Blinking Nanoparticles.

Localization-based ultrasound imaging methods that use microbubbles or nanodroplets offer high-resolution imaging with improved sensitivity and reduced background signal. However, these methods require long acquisition times (typically seconds to minutes), preventing their use for real-time imaging and, thus, limiting their clinical translational potential. Here, we present a new ultrafast localization method using blinking ultrasound-responsive nanoparticles (BNPs). When activated with high frame rate (1 kHz) plane wave ultrasound pulses with a mechanical index of 1.5, the BNPs incept growth of micrometer-sized bubbles, which in turn collapse and generate a blinking ultrasound signal. We showed that background-free ultrasound images could be obtained by localizing these blinking events using acquisition times as low as 11 ms. In addition, we demonstrated that BNPs enable in vivo background-free ultrasound imaging in mice. We envision that BNPs will facilitate the clinical translation of localization-based ultrasound imaging for more sensitive detection of cancer and other diseases.

First experiments with carbon black pigment dispersion acting as a Janus ultrasound contrast agent

Abstract Background: Theranostic ultrasound contrast agents comprise a therapeutic component whose controlled release is triggered by an ultrasound pulse. However, once the therapeutic component has been released from an ultrasound contrast agent microbubble, its intended uptake cannot be monitored, as its acoustically active host has been destroyed. Acoustic Janus particles, whose hydrophobic and hydrophilic properties depend on the external acoustic regime, are of potential use as contrast agents and drug-delivery tracers. The purpose of this study was to evaluate the hypothesis that submicron particles with Janus properties may act as ultrasound contrast agents whose hydrophobicity changes over time. Methods: Fifty samples of carbon black were subjected to 5-minute sonication with pulses with a center frequency of 10 MHz and a 1% duty cycle, after which the optical absorption coefficients were measured in n-octanol and water. These coefficients were compared with those of unsonicated samples. Results: Our preliminary results show that the difference between the linear absorption coefficients of sonicated and unsonicated samples was Δα = 80 ± 13 m−1 immediately after sonication, indicating that the carbon black particles were less hydrophobic after sonication than prior to it. Forty-eight hours after sonication, the difference in linear optical absorption coefficients had lessened to Δα = 16 ± 9 m−1, indicating that the carbon black particles had become more hydrophobic over time, but not equal to the hydrophobicity situation prior to sonication. Conclusion: The experiments confirmed that submicron carbon black particles have acoustic Janus properties.

Effect of Ultrasound Pulse Length on Sonoreperfusion Therapy.

In recent years, long- and short-pulse ultrasound (US)-targeted microbubble cavitation (UTMC) has been found to increase perfusion in healthy and ischemic skeletal muscle, in pre-clinical animal models of microvascular obstruction and in the myocardium of patients presenting with acute myocardial infarction. There is evidence that the observed microvascular vasodilation is driven by the nitric oxide pathway and purinergic signaling, but the time course of the response and the dependency on US pulse length are not well elucidated. Because our prior data supported that sonoreperfusion efficacy is enhanced by long-pulse US versus short-pulse US, in this study, we sought to compare long-pulse (5000 cycles) and short-pulse (500×10 cycles) US at a pressure of 1.5 MPa with an equivalent total number of acoustical cycles, hence constant acoustic energy, and at the same frequency (1 MHz), in a rodent hind limb model with and without microvascular obstruction (MVO). In quantifying perfusion using burst replenishment contrast-enhanced US imaging, we made three findings: (i) Long and short pulses result in different vasodilation kinetics in an intact hind limb model. The long pulse causes an initial spasmic reduction in flow that spontaneously resolved at 4 min, followed by sustained higher flow rates (approximately twofold) compared with baseline, starting 10 min after therapy (p < 0.05). The short pulse caused a short-lived approximately twofold increase in flow rate that peaked at 4 min (p < 0.05), but without the initial spasm. (ii) The sustained increased response with the long pulse is not simply reactive hyperemia. (iii) Both pulses are effective in reperfusion of MVO in our hindlimb model by restoring blood volume, but only the long pulse caused an increase in flow rate after treatment ii, compared with MVO (p < 0.05). Histological analysis of hind limb muscle post-UTMC with either pulse configuration indicates no evidence of tissue damage or hemorrhage. Our findings indicate that the microbubble oscillation induces vasodilation, and therapeutic efficacy for the treatment of MVO can be tuned by varying pulse length; relative to short-pulse US, longer pulses drive greater microbubble cavitation and more rapid microvascular flow rate restoration after MVO, warranting further optimization of the pulse length for sonoreperfusion therapy.

Influence of ultrasound modes on sonoelectrochemical degradation of Congo red and palm oil mill effluent

Sonoelectrochemical oxidation (SEO) treatment is a competitive technology for the degradation of organic pollutants in water. The operation modes of ultrasound (continuous and pulse) not only affect the pollutant degradation efficiency but also the energy consumption of SEO. In this study, the influence of ultrasound modes on SEO degradation of Congo red (CR) and real wastewater – palm oil mill effluent (POME) were investigated. The SEO was operated in two modes: continuous ultrasound throughout the whole process and intermittent ultrasound at a cycle of 15 min of ultrasound and 5 min without ultrasound. It was found that the intermittent SEO gave a higher degree of degradation of CR at 95% as compared to continuous SEO and electrochemical oxidation (EO) at 85% and 64%, respectively. The improved performance could be attributed to the supply of ultrasound that minimized electrode passivation and promoted mass transfer and production of hydroxyl radicals. The intermittent supply of ultrasound diminished the interference of ultrasound on the electrochemical process. A similar observation was also observed where the highest COD reduction of POME was recorded by intermittent SEO at about 65%. In terms of energy consumption, degradation of CR by SEO only required half of the energy consumed by the analogous purely electrochemical process at 250–265 kWh/kg dye removed. Surprisingly, the energy consumption for SEO degradation of POME only reduced from 32.82 (electrochemical) to 25.91 and 30.78 kWh/kg COD removed for continuous and intermittent SEO, respectively. Such contrast in energy saving highlights the need for further study as the complex constituents of real effluents will result in different SEO treatment performance. Nonetheless, the capability of SEO in reducing the COD indicates its potential to be used as pre- or post-treatment for other advanced processes in POME handling.

Fundamental validation of flow volume measurement by ultrasound pulse Doppler method using simulated circuit

Fundamental validation of flow volume measurement by ultrasound pulse Doppler method using simulated circuit

Comparison of spatial encodings for ultrasound imaging.

Ultrasound pulse sequencing and receive signal focusing work hand-in-hand to determine image quality. These are commonly linked by geometry, for example using focused beams or planewaves in transmission paired with appropriate time-of-flight calculations for focusing. Spatial encoding allows a broader class of array transmissions but requires decoding of the recorded echoes before geometric focusing can be applied. Recent work has expanded spatial encoding to include not only element apodizations but also element time delays. This powerful technique allows for a unified beamforming strategy across different pulse sequences and increased flexibility in array signal processing given access to estimates of individual transmit element signals, but trade-offs in image quality between these encodings has not been previously studied. We evaluate in simulation several commonly used time delay and amplitude encodings and investigate optimization of the parameter space for each. Using signal-to-noise ratio, point resolution, and lesion detectability we found trade-offs between focused beams, planewaves, and Hadamard weight encodings. Beams with broader geometries maintained a wider field-of-view after decoding at the cost of signal-to-noise ratio (SNR) and lesion detectability. Focused beams and planewaves showed slightly reduced resolution compared to Hadamard weights in some cases, especially close to the array. We also found overall degraded image quality using random weight or random delay encodings. We validate these findings with experimental phantom imaging for select cases. We believe that these findings provide a starting point for sequence optimization and for improved image quality using the spatial encoding approach for imaging.

Acoustic thermometer operating up to 11 m: uncertainty assessment and new values for Cramer coefficients around 40 kHz

The present article describes an acoustic thermometer to measure the average air temperature integrated along a path ranging from 1 m to 11 m. It is based on time-of-flight measurement of ultrasound pulses at frequencies close to 40 kHz. Several methods for the detection of arrival times were investigated, notably cross-correlation and cross-spectrum. The uncertainty of the instrument itself, independent of that of the Cramer equation has been estimated at between 0.13 K to 0.09 K for distances ranging from 3 m to 11 m respectively. In practice, an experimental comparison with Pt100 probes (uncertainty of 0.1 K) has shown that the estimated uncertainty levels are relatively compatible, although the linearity of the system does not appear to be very good. To solve this problem, appropriate values for the Cramer coefficients a0 and a1 for an acoustic frequency of about 40 kHz have been determined, which contributes to improved knowledge of this equation as a function of acoustic frequency.

Axial Super-Resolution Ultrasound Imaging With Quasi-Monopolar Pulses From a Dual-Frequency Transducer

In biomedical ultrasound imaging, the axial resolution is determined by the pulse length, which reaches the bottleneck for the existing piezoelectric materials. The resonance of piezoelectric materials in conventional ultrasound transducers causes relatively long pulses with multiple wavelengths, which cannot be effectively shortened for decades. The waveform with practically the shortest pulse length is a monopolar half-cycle sinusoidal wave, which is beyond the capability of traditional piezoelectric transducers. Here, we propose a method for generating quasi-monopolar ultrasound pulses by the superposition of two ultrasound signals from a stack-layer dual-frequency ultrasound transducer. In this article, we designed and fabricated a 1+ 3 MHz stack-layer dual-frequency ultrasound transducer, and validated the generation of the quasi-monopolar pulse by specific excitation of each piezoelectric layer. Imaging with the quasi-monopolar pulses on copper wire phantoms demonstrated a pulse length of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.17\lambda $ </tex-math></inline-formula> (85.5 ns referring to 2 MHz), which generates images with superb axial resolution and clearly differentiates the phantom wires separated with 1 mm. This design provides a practical approach for general-purpose super-resolution ultrasound imaging without a contrast agent.

Autonomous healing by vascular networks: tracking of cracks interaction by Ultrasounds and Acoustic Emission

The tracking of healing on concrete slabs where dense crack patterns are formed under bending is reported using Acoustic Emission (AE) and Ultrasound Pulse Velocity (UPV). Additively manufactured polymeric networks are designed to distribute a polyurethane agent through capillary actions and under pressure to the open cracks, formed in the slabs. It is shown that the crack pattern is controlled by the geometry of the vascular networks that are positioned near the steel reinforcement. The activation of both conventional linear and interlinked web-shaped networks is monitored by AE, however in both cases the load at which the initial cracks form is lower in series with embedded networks compared to the reference series, an indication of an overall weakening effect. The area where the healing agent circulates is larger (300x400 mm2) than past tests on beams, but only local healing is evident by UPV mapping. An indirect proof of cracks filling with stiffened agent is provided by the AE pencil-lead breaking test, as the amplitude recovery after healing can be linked to crack closure. This preliminary work evaluates the design of 3D printed vascular networks, but also explores the potential of AE and UPV as inspection tools in healing studies.