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Our previous methodology in local sound speed estimation utilized time delays measured by the cross correlation of delayed full-synthetic aperture channel data to estimate the average speed of sound. However, focal distortions in this methodology lead to biased estimates of the average speed of sound, which, in turn, leads to biased estimates of the local speed of sound. Here, we demonstrate the bias in the previous methodology and introduce a coherence-based average sound speed estimator that eliminates this bias and is computationally much cheaper in practice. Because this coherence-based approach estimates the average sound speed in the medium over an equally spaced grid in depth rather than time, we derive a refined model that relates the local and average speeds of sound as a function of depth in layered media. A fast, closed-form inversion of this model yields highly accurate local sound speed estimates. The root-mean-square (rms) error of local sound speed reconstruction in simulations of two-layer media is 4.6 and 2.5 m/s at 4 and 8 MHz, respectively. This work examines the impact of frequency, f -number, aberration, and reverberation on sound speed estimation. Phantom and in vivo experiments in rats further validate the coherence-based sound speed estimator.

Passive cavitation mapping (PCM) techniques typically utilize a time-exposure acoustic (TEA) approach, where the received radio-frequency data is beamformed, squared, and integrated over time. Such PCM-TEA cavitation maps typically suffer from long tail artifacts and poor axial resolution with pulse-echo diagnostic arrays. Here, we utilize a recently developed PCM technique based on cavitation source localization (CSL), which fits a hyperbolic function to the received cavitation wavefront. A filtering method based on the root-mean-squared error (rmse) of the hyperbolic fit is utilized to filter out spurious signals. We apply a wavefront correction technique to the signals with poor fit quality to recover additional cavitation signals and improve cavitation localization. Validation of the PCM-CSL technique with rmse filtering and wavefront correction was conducted in experiments with a tissue-mimicking flow phantom and an in vivo mouse model of cancer. It is shown that the quality of the hyperbolic fit, necessary for the PCM-CSL, requires an rmse

Passive cavitation mapping (PCM) algorithms for diagnostic ultrasound arrays based on time exposure acoustics (TEA) exhibit poor axial resolution, which is in part due to the diffraction-limited point spread function of the imaging system and poor rejection by the delay-and-sum beamformer. In this article, we adapt a method for speed of sound estimation to be utilized as a cavitation source localization (CSL) approach. This method utilizes a hyperbolic fit to the arrival times of the cavitation signals in the aperture domain, and the coefficients of the fit are related to the position of the cavitation source. Wavefronts exhibiting poor fit to the hyperbolic function are corrected to yield improved source localization. We demonstrate through simulations that this method is capable of accurate estimation of the origin of coherent spherical waves radiating from cavitation/point sources. The average localization error from simulated microbubble sources was 0.12 ± 0.12mm ( $0.15\,\,\pm \,\, 0.14\lambda _{0}$ for a 1.78-MHz transmit frequency). In simulations of two simultaneous cavitation sources, the proposed technique had an average localization error of 0.2mm ( $0.23\lambda _{0}$ ), whereas conventional TEA had an average localization error of 0.81mm ( $0.97\lambda _{0}$ ). The reconstructed PCM-CSL image showed a significant improvement in resolution compared with the PCM-TEA approach.

Ultrasound and microbubble (USMB)-mediated drug delivery is a valuable tool for increasing the efficiency of the delivery of therapeutic agents to cancer while maintaining low systemic toxicity. Typically, selection of USMB drug delivery parameters used in current research settings are either based on previous studies described in the literature or optimized using tissue-mimicking phantoms. However, phantoms rarely mimic in vivo tumor environments, and the selection of parameters should be based on the application or experiment. In the following study, we optimized the therapeutic parameters of the ultrasound drug delivery system to achieve the most efficient in vivo drug delivery using fluorescent semiconducting polymer nanoparticles as a model nanocarrier. We illustrate that voltage, pulse repetition frequency and treatment time (i.e., number of ultrasound pulses per therapy area) delivered to the tumor can successfully be optimized in vivo to ensure effective delivery of the semiconducting polymer nanoparticles to models of hepatocellular carcinoma. The optimal in vivo parameters for USMB drug delivery in this study were 70 V (peak negative pressure = 3.4 MPa, mechanical index = 1.22), 1-Hz pulse repetition frequency and 100-s therapy time. USMB-mediated drug delivery using in vivo optimized ultrasound parameters caused an up to 2.2-fold (p0.01) increase in drug delivery to solid tumors compared with that using phantom-optimized ultrasound parameters.

Surgery to treat drug-resistant epilepsy can be quite effective but remains substantially underutilized. A pilot study was undertaken to test the feasibility of using a non-invasive, non-ablative, approach to produce focal neuronal loss to treat seizures in a rodent model of temporal lobe epilepsy. In this study, spontaneous, recurrent seizures were established in a mouse model of pilocarpine-induced status epilepticus. After post-status epilepticus stabilization, baseline behavioral seizures were monitored for 30 d. Non-invasive opening of the blood–brain barrier targeting the hippocampus was then produced by using magnetic resonance-guided, low-intensity focused ultrasound, through which a neurotoxin (quinolinic acid) administered intraperitoneally gained access to the brain parenchyma to produce focal neuronal loss. Behavioral seizures were then monitored for 30 d after this procedure, and brains were subsequently prepared for histologic analysis of the sites of neuronal loss. The average frequency of behavioral seizures in all animals (n = 11) was reduced by 21.2%. Histologic analyses along the longitudinal axis of the hippocampus revealed that most of the animals (n = 8) exhibited neuronal loss located primarily in the intermediate aspect of the hippocampus, while sparing the septal aspect. Two other animals with damage to the intermediate hippocampus also exhibited prominent bilateral damage to the septal aspect of the hippocampus. A final animal had negligible neuronal loss overall. Notably, the site of neuronal loss along the longitudinal axis of the hippocampus influenced seizure outcomes. Animals that did not have bilateral damage to the septal hippocampus displayed a mean decrease in seizure frequency of 27.7%, while those with bilateral damage to the septal hippocampus actually increased seizure frequency by 18.7%. The animal without neuronal loss exhibited an increase in seizure frequency of 19.6%. The findings indicate an overall decrease in seizure frequency in treated animals. And, the site of neuronal loss along the longitudinal axis of the hippocampus appears to play a key role in reducing seizure activity. These pilot data are promising, and they encourage additional and more comprehensive studies examining the effects of targeted, non-invasive, neuronal lesions for the treatment of epilepsy.

Intravascular acoustic radiation force impulse (IV-ARFI) imaging has the potential to identify vulnerable atherosclerotic plaques and improve clinical treatment decisions and outcomes for patients with coronary heart disease. Our long-term goal is to develop a thin, flexible catheter probe that does not require mechanical rotation to achieve high-resolution IV-ARFI imaging. In this work, we propose a novel cylindrical transducer array design for IV-ARFI imaging and investigate the feasibility of this approach. We present the construction of a 2.2-mm-long, 4.6-Fr cylindrical prototype transducer to demonstrate generating large ARFI displacements from a small toroidal beam, and we also present simulations of the proposed IV-ARFI cylindrical array design using Field II and a cylindrical finite-element model of vascular tissues and soft plaques. The prototype transducer was found to generate peak radial displacements of over $10~\mu \text{m}$ in soft gelatin phantoms, and simulations demonstrate the ability of the array design to obtain ARFI images and distinguish soft plaque targets from surrounding, stiffer vessel wall tissue. These results suggest that high-resolution IV-ARFI imaging is possible using a cylindrical transducer array.

In this study, we designed and validated a platform for ultrasound and microbubble-mediated delivery of FDA-approved pegylated poly lactic-co-glycolic acid (PLGA) nanoparticles loaded with anticancer microRNAs (miRNAs) to deep tissues in a pig model. Small RNAs have been shown to reprogram tumor cells and sensitize them to clinically used chemotherapy. To overcome their short intravascular circulation half-life and achieve controlled and sustained release into tumor cells, anticancer miRNAs need to be encapsulated into nanocarriers. Focused ultrasound combined with gas-filled microbubbles provides a noninvasive way to improve the permeability of tumor vasculature and increase the delivery efficiency of drug-loaded particles. A single handheld, curvilinear ultrasound array was used in this study for image-guided therapy with clinical-grade SonoVue contrast agent. First, we validated the platform on phantoms to optimize the microbubble cavitation dose based on acoustic parameters, including peak negative pressure, pulse length, and pulse repetition frequency. We then tested the system in vivo by delivering PLGA nanoparticles co-loaded with antisense-miRNA-21 and antisense-miRNA-10b to pig liver and kidney. Enhanced miRNA delivery was observed (1.9- to 3.7-fold increase) as a result of the ultrasound treatment compared to untreated control regions. Additionally, we used highly fluorescent semiconducting polymer nanoparticles to visually assess nanoparticle extravasation. Fluorescent microscopy suggested the presence of nanoparticles in the extravascular compartment. Hematoxylin and eosin staining of treated tissues did not reveal tissue damage. The results presented in this manuscript suggest that the proposed platform may be used to safely and noninvasively enhance the delivery of miRNA-loaded nanoparticles to target regions in deep organs in large animal models.

Spatially localized microbubble cavitation by ultrasound offers an effective means of altering permeability of natural barriers (i.e. blood vessel and cell membrane) in favor of nanomaterials accumulation in the target site. In this study, a clinically relevant, minimally invasive ultrasound guided therapeutic approach is investigated for targeted delivery of anticancer microRNA loaded PLGA-b-PEG nanoparticles to spontaneous hepatocellular neoplasia in a canine model. Quantitative assessment of the delivered microRNAs revealed prominent and consistent increase in miRNAs levels (1.5-to 2.3-fold increase (p

We studied the paracrine function of mesenchymal stem cells (MSCs) derived from various sources in response to pulsed focused ultrasound (pFUS). Human adipose tissue (AD), bone marrow (BM), and umbilical cord (UC) derived MSCs were exposed to pFUS at two intensities: 0.45 W/cm2 ISATA (310 kPa PNP) and 1.3 W/cm2 ISATA (540 kPa PNP). Following pFUS, the viability and proliferation of MSCs were assessed using a hemocytometer and confocal microscopy, and their secreted cytokine profile determined using a multiplex ELISA. Our findings showed that pFUS can stimulate the production of immunomodulatory, anti-inflammatory, and angiogenic cytokines from MSCs which was dependent on both the source of MSC being studied and the acoustic intensity employed. These important findings set the foundation for additional mechanistic and validation studies using this novel noninvasive and clinically translatable technology for modulating MSC biology.

Objective. Speed of sound has previously been demonstrated to correlate with fat concentration in the liver. However, estimating speed of sound in the liver noninvasively can be biased by the speed of sound of the tissue layers overlying the liver. Here, we demonstrate a noninvasive local speed of sound estimator, which is based on a layered media assumption, that can accurately capture the speed of sound in the liver. We validate the estimator using an obese Zucker rat model of non-alcoholic fatty liver disease and correlate the local speed of sound with liver steatosis. Approach. We estimated the local and global average speed of sound noninvasively in 4 lean Zucker rats fed a normal diet and 16 obese Zucker rats fed a high fat diet for up to 8 weeks. The ground truth speed of sound and fat concentration were measured from the excised liver using established techniques. Main Results. The noninvasive, local speed of sound estimates of the livers were similar in value to their corresponding ‘ground truth’ measurements, having a slope ± standard error of the regression of 0.82 ± 0.15 (R 2 = 0.74 and p < 0.001). Measurement of the noninvasive global average speed of sound did not reliably capture the ‘ground truth’ speed of sound in the liver, having a slope of 0.35 ± 0.07 (R 2 = 0.74 and p < 0.001). Decreasing local speed of sound was observed with increasing hepatic fat accumulation (approximately −1.7 m s−1 per 1% increase in hepatic fat) and histopathology steatosis grading (approximately −10 to −13 m s−1 per unit increase in steatosis grade). Local speed of sound estimates were highly correlated with steatosis grade, having Pearson and Spearman correlation coefficients both ranging from −0.87 to −0.78. In addition, a lobe-dependent speed of sound in the liver was observed by the ex vivo measurements, with speed of sound differences of up to 25 m s−1 (p < 0.003) observed between lobes in the liver of the same animal. Significance. The findings of this study suggest that local speed of sound estimation has the potential to be used to predict or assist in the measurement of hepatic fat concentration and that the global average speed of sound should be avoided in hepatic fat estimation due to significant bias in the speed of sound estimate.

Background The aim of this study was to examine the effect of a three-step approach that utilizes the application of adipose tissue-derived mesenchymal stem cells (AD-MSCs), encapsulation, and pulsed focused ultrasound (pFUS) to help the engraftment and function of transplanted islets. Methods In step 1, islets were co-cultured with AD-MSCs to form a coating of AD-MSCs on islets: here, AD-MSCs had a cytoprotective effect on islets; in step 2, islets coated with AD-MSCs were conformally encapsulated in a thin layer of alginate using a co-axial air-flow method: here, the capsule enabled AD-MSCs to be in close proximity to islets; in step 3, encapsulated islets coated with AD-MSCs were treated with pFUS: here, pFUS enhanced the secretion of insulin from islets as well as stimulated the cytoprotective effect of AD-MSCs. Results Our approach was shown to prevent islet death and preserve islet functionality in vitro. When 175 syngeneic encapsulated islets coated with AD-MSCs were transplanted beneath the kidney capsule of diabetic mice, and then followed every 3 days with pFUS treatment until day 12 post-transplantation, we saw a significant improvement in islet function with diabetic animals re-establishing glycemic control over the course of our study (i.e., 30 days). In addition, our approach was able to enhance islet engraftment by facilitating their revascularization and reducing inflammation. Conclusions This study demonstrates that our clinically translatable three-step approach is able to improve the function and viability of transplanted islets.

Pulsed focused ultrasound (pFUS) utilizes short cycles of sound waves to mechanically shake cells within tissues which, in turn, causes transient local increases in cytokines, growth factors and cell adhesion molecules. Although the effect of pFUS has been investigated in several different organs including the kidney, muscle and heart, its effect on the pancreas has not been investigated. In the present work, we applied pFUS to the rodent pancreas with the following parameters: 1.1-MHz frequency, 5-Hz pulse repetition frequency, 5% duty cycle, 10-ms pulse length, 160-s duration. Low-intensity pFUS had a spatial average temporal average intensity of 11.5 W/cm2 and a negative peak pressure of 3 MPa; high-intensity pFUS had a spatial average temporal average intensity of 18.5 W/cm2 and negative peak pressure of 4 MPa. Here we found that pFUS changed the expression of several cytokines while having no effect on the underlying tissue histology or health of pancreatic cells (as reflected by no significant change in plasma levels of amylase and lipase). Furthermore, we found that this effect on cytokine expression in the pancreas was acoustic intensity dependent; while pFUS at low intensities turned off the expression of several cytokines, at high intensities it had the opposite effect and turned on the expression of these cytokines. The ability to non-invasively manipulate the microenvironment of the pancreas using sound waves could have profound implications for priming and modulating this organ for the application of cellular therapies in the context of both regenerative medicine (i.e., diabetes and pancreatitis) and oncology (i.e., pancreatic cancer).

In order to obtain more reliable values of diamond’s third-order elastic constants, experiments on bulk acoustic wave propagation under uniaxial stress application (up to 450 MPa) in pure IIa-type synthetic single-crystal diamond were carried out, and values of third-order elastic constants were calculated. We have also provided theoretical analysis using ab initio density functional theory approach which has shown close correspondence with the experimentally measured data. From ab initio calculations, the values of third-order elastic constants are (GPa): C 111 = −7611, C 112 = −1637, C 144 = −199, C 155 = −2799, C 123 = 604, C 456 = −1148, while experimental values are C 111 = −7750 ± 750, C 112 = −2220 ± 500, C 144 = −1780 ± 440, C 155 = −2800 ± 220, C 123 = 2100 ± 200, C 456 = −30 ± 150. The estimated values on diamond’s fourth-order elastic constants were obtained. The calculated stress–strain curves for different crystal orientations were investigated, including shear stress for [111] direction. From calculations for [100], [110], and [111] directions, the values of critical stress in case of the pure shear were estimated as 222, 113, and 84 GPa, respectively.

This study demonstrates that pulsed focused ultrasound (pFUS) therapy can non-invasively enhance the function and engraftment of pancreatic islets following transplantation. In vitro, we show that islets treated with pFUS at low (peak negative pressure (PNP): 106kPa, spatial peak temporal peak intensity (Isptp): 0.71 W/cm2), medium (PNP: 150kPa, Isptp: 1.43 W/cm2) or high (PNP: 212kPa, Isptp: 2.86 W/cm2) acoustic intensities were stimulated resulting in an increase in their function (i.e. insulin secretion at low-intensity: 1.15 ± 0.17, medium-intensity: 2.02 ± 0.25, and high-intensity: 2.54 ± 0.38 fold increase when compared to control untreated islets; P 2+) within islets which was also linked to pFUS increasing the resting membrane potential (Vm) of islets. Following syngeneic renal sub-capsule islet transplantation in C57/B6 mice, pFUS (PNP: 2.9 MPa, Isptp: 895 W/cm2) improved the function of transplanted islets with diabetic animals rapidly re-establishing glycemic control. In addition, pFUS was able to enhance the engraftment by facilitating islet revascularization and reducing inflammation. Given a significant number of islets are lost immediately following transplantation, pFUS has the potential to be used in humans as a novel non-invasive therapy to facilitate islet function and engraftment, thereby improving the outcome of diabetic patients undergoing islet transplantation.

In this study, we designed and validated a platform for ultrasound (US) and microbubble (MB)-mediated delivery of FDA-approved pegylated poly lactic-co-glycolic acid (PLGA) nanoparticles (NPs) loaded with anticancer microRNAs (miRNAs) to deep tissues in a pig model. Small RNAs have the ability to reprogram tumor cells and sensitize them to clinically used chemotherapy. However, to overcome their short intravascular circulation half-life and achieve controlled and sustained release into tumor cells, anticancer miRNAs need to be encapsulated into NPs. Moreover, focused US combined with gas-filled MBs provides a safe and noninvasive way to improve the permeability of tumor vasculature and increase the delivery efficiency of drug-loaded nanocarriers. A single handheld, curvilinear US array was used in this study for image-guidance and therapy with clinical-grade SonoVue MBs. First, we validated the platform on phantoms to optimize the MB cavitation dose based on acoustic parameters, including peak negative pressure, pulse length, and pulse repetition frequency. We then tested the system in vivo by delivering PLGA-NPs co-loaded with antisense-miRNA-21 and antisense-miRNA-10b in pig liver and kidney. Enhanced miRNA delivery was observed (1.9- to 3.7-fold increase) as a result of the US-MB treatment compared to untreated control regions. Additionally, we used highly fluorescent semiconducting polymer nanoparticles (SPNs) co-delivered with miRNA-loaded PLGA-NPs to visually assess NP delivery. Fluorescent microscopy of SPNs confirmed NP extravasation and showed the presence of particles in the extravascular compartment. Hematoxylin and eosin staining of treated tissues did not reveal tissue damage. The results presented in this manuscript suggest that enhanced delivery of miRNA-loaded NPs to target regions in deep organs is feasible in large animal models using the proposed platform.

We have fabricated a cylindrical intravascular ultrasound (IVUS) transducer array prototype capable of generating an acoustic radiation force impulse (ARFI) for shear wave elasticity imaging (SWEI). The prototype array was a 4-mm long, 2.5-mm diameter, 4 MHz PZT-8 tube, axially segmented into 12 elements on a 334 µm pitch. This transducer array was used in custom vessel phantoms and in ex vivo porcine artery experiments to investigate the potential for IVUS SWEI to distinguish soft lipid cores from stiffer surrounding tissues. By using this array transducer to generate a radially-directed ARFI “push”, and a Verasonics linear array probe to track displacements in planes parallel to the “push”, SWEI images of a vessel phantom with hard vessel walls and a soft inclusion were obtained. In tissue-mimicking phantoms, focusing the transducer array to a range of 5 mm generated ARFI displacements up to 1.36 and 1.76 times greater than unfocused excitations in the soft and stiff regions, respectively. The measured shear wave speed in the soft inclusion and stiff vessel wall was 0.97±0.59 m/s and 1.66±0.91 m/s, respectively, and was close to the calibrated measurements of 1.21±0.05 m/s and 1.56±0.05 m/s, respectively. A SWEI image of an ex vivo porcine renal artery was obtained using the prototype transducer and external tracking array, and showed an average shear wave speed of 3.97±1.12 m/s. These results demonstrate the potential of this IVUS array to enable SWEI, to quantifiably assess vulnerable vascular plaques.

In this paper, we adapt and validate a platform for ultrasound (US)and microbubble (MB)-mediated delivery of drug-loaded poly lactic-co-glycolic acid nanoparticles (NPs)to liver cancer in a large animal model as a further step toward clinical translation. A single-probe ultrasound setup was used for image-guided NP delivery using clinically approved MBs. Acoustic parameters were optimized in a phantom study. Experiments were conducted in a healthy pig model to validate the platform and test the delivery efficacy in vivo. The US/MB treatment resulted in 1.9-fold increase in expression of exogenous anticancer microRNA with respect to an untreated liver region and 1884-fold increase relative to a control animal.

Acoustic attenuation in a multifrequency bulk acoustic wave resonator based on the synthetic diamond single crystal is investigated. The acoustic energy loss in a layered piezoelectric Al/AlN/Mo/(001) diamond structure is analyzed. The depth of a damaged surface layer with a thickness of 20–30 nm in diamond after abrasive finishing is estimated using high-energy electron backscattered diffraction and observation of Kikuchi lines. The estimation shows that the acoustic energy loss at a diamond substrate roughness of up to 20 nm, as well as acoustic loss in thin films, is lower than the bulk acoustic attenuation by an order of magnitude and is of no fundamental importance. However, the surface roughness of the piezoelectric AlN film can contribute comparably with the bulk attenuation in the substrate. It is demonstrated that the transition from the Akhiezer to Landau–Rumer regime in diamond occurs at a frequency of ~1 GHz and the phonon–phonon relaxation time is ~1.6 × 10–10 s. Calculation of acoustic attenuation showed that, although at a frequency of ~1 GHz the acoustic loss in diamond is somewhat higher than in well-known materials with a low attenuation level, the loss in diamond becomes noticeably lower as frequency increases to 8–10 GHz. The obtained maximum experimental value Qf ≈ 10 × 1013 Hz (9.5 GHz) makes synthetic diamond promising for microwave acoustoelectronic devices.

Conventional ultrasound imaging transducers are fabricated using planar geometries—of materials and in most subsequent processing (bonding, dicing, etc.); this can lead to complications in assembling catheter- or endoscope-based devices, and/or significant inherent limitations in their design and application. Miniature cylindrical transducer devices offer the potential for more straightforward design for 360-deg imaging applications, albeit with unique fabrication challenges. We have developed a novel technique for processing cylindrical ultrasound transducer geometries, and used it to fabricate prototype devices designed for intravascular and endolumenal applications. We created a custom dicing setup allowing a tube of radially poled piezoceramic (PZT-4) as small as 4.6 Fr (1.53 mm diameter) to be cut circumferentially, to a specified depth or completely through the wall of the tube, at precise axial locations. The resulting cylindrical transducer was connected to a function generator and power amplifier, and driven at 7.5 MHz to generate axisymmetric, radially directed acoustic radiation force impulse (ARFI) displacements up to 19 μm in a tissue-mimicking elasticity phantom. This demonstrates that miniature cylindrical transducers can be made to enable 360-deg elasticity imaging of the mechanical properties and structure of tissues, to identify vulnerable atherosclerotic plaques or quantify softening of the cervix prior to labor onset.Conventional ultrasound imaging transducers are fabricated using planar geometries—of materials and in most subsequent processing (bonding, dicing, etc.); this can lead to complications in assembling catheter- or endoscope-based devices, and/or significant inherent limitations in their design and application. Miniature cylindrical transducer devices offer the potential for more straightforward design for 360-deg imaging applications, albeit with unique fabrication challenges. We have developed a novel technique for processing cylindrical ultrasound transducer geometries, and used it to fabricate prototype devices designed for intravascular and endolumenal applications. We created a custom dicing setup allowing a tube of radially poled piezoceramic (PZT-4) as small as 4.6 Fr (1.53 mm diameter) to be cut circumferentially, to a specified depth or completely through the wall of the tube, at precise axial locations. The resulting cylindrical transducer was connected to a function generator and power amplifier...

The Me1/AlN/Me2/(100) diamond structure has been theoretically analyzed and experimentally investigated in the range 0.5–10 GHz using high-overtone bulk acoustic resonators with different electrodes topologies based on the Al/AlN/Mo/(100) diamond structure. The maximum quality parameter Q × f ≈ 1014 Hz was obtained at f = 9.5 GHz. The layered structure has been analyzed using the developed HBAR software v. 2.3. It is demonstrated that the features in the frequency dependences of the parameters of such resonators are related to the behavior of a loaded thin-film piezoelectric transducer. The calculation results are in good agreement with the experiment. The frequency dependences of the equivalent parameters of the resonators have been calculated. It is shown that the synthetic type IIa diamond single crystal in combination with aluminum nitride is promising for implementation of high-Q acoustoelectronic microwave devices.

Displacement estimation is a critical component of elastography. The measurement of sub-resolution displacements relies on high cross-correlation (CC) between repeated collinear RF acquisitions. CCs are degraded by common sources of acoustic noise, such as reverberation clutter, in addition to the displacement of scatterers within the radiation force field. CCs are also degraded spatially across the aperture when imaging diffuse scatterers. Previously, we proposed a method that defines an equivalent CC calculation utilizing the CCs of the individual channel signals. In this method, poor CCs are rejected from the channel-signal pairs, resulting in reduced jitter in simulation experiments. Here, we characterize the performance of the channel-based method in radiation force displacement estimation in a phantom study under ideal and noisy imaging conditions.

Cardiovascular disease, including atherosclerosis and critical limb ischemia, affects millions of people worldwide. There is a clinical need to base treatment decisions on quantitative analysis of the plaque composition. However, no reliable clinical methods to quantify the mechanical properties of plaque components and detect plaque vulnerability currently exist, particularly for coronary disease. Here we demonstrate the measurement of shear waves generated by acoustic radiation force (ARF) from an intravascular ultrasound (IVUS) transducer prototype, as a potential means to quantifiably assess vascular plaques.

The linear and nonlinear elastic properties of B4C boron carbide ceramics have been studied. The second-order elastic constants and other parameters of the theory of elasticity in the linear approximation have been calculated based on the experimentally measured density and velocity values of longitudinal and shear bulk acoustic waves in the samples. The Thurston-Brugger method has been used to determine the third-order elastic constants of B4C. To achieve this, we have measured the relative changes of the longitudinal and shear bulk acoustic wave velocities depending on the uniaxial compression applied to the sample.

The presence of spurious peaks in the amplitude-frequency response of diamond based piezoelectric layered structure was shown. Excitation of such peaks results in deterioration of an useful acoustical signal. It was shown that such spurious peaks should be associated with Lamb waves in a layered structure. By means of FEM analysis, the propagation of acoustic waves of different types in the piezoelectric layered structure “Al/AlN/Mo/(100) diamond” has been investigated in detail. By analyzing the elastic displacement patterns at frequencies from 0 up to 250 MHz, a set of all the possible acoustic waves, especially Lamb modes, have been studied, and dispersive curves of phase velocity have been plotted. A revised classification of Lamb modes has been introduced.

Temperature coefficients of elastic constants (TC(IJ)) for trigonal, hexagonal, and tetragonal crystals have been obtained. The TC(IJ) of several trigonal, hexagonal, and tetragonal crystals have been calculated and compared with known experimental data. The nature of the anomalous TC66 of quartz has been discussed in detail.

To extend the theory of the temperature dependence of the elastic constants in cubic crystals beyond the second- and third-order elastic constants, the fourth-order elastic constants, as well as the non-linearity in the thermal expansion temperature dependence, have been taken into account. Theoretical results were represented as temperature functions of the effective elastic constants and compared with experimental data for a number of cubic crystals, such as alkali metal halides, and elements gold and silver. The relations obtained give a more accurate description of the experimental temperature dependences of second-order elastic constants for a number of cubic crystals, including deviations from linear behavior. A good agreement between theoretical estimates and experimental data has been observed.

The piezoelectric layered structure Me1/AlN/Me2/single crystalline diamond was developed. Acoustic properties of number the layered structures have been studied on microwave frequency band. The frequency dependence of quality factor was estimated as Q·f ≈ 5.6·1013. The pressure and temperature influence on the resonant frequency have been studied. First resonant overtones with Q ~ 2500 were observed on super high frequencies ~ 19.5 GHz.

Features of bulk acoustic wave propagation in the LiTaO3 single crystal were studied. Changes of BAW velocities caused by the application of uniaxial pressure or dc electric field were measured. Third-order elastic constants and some nonlinear piezoelectric constants of LTO single crystal were calculated.

The features of bulk acoustic wave (BAW) propagation in crystals of symmetry 3m under uniaxial pressure at room temperature were examined. Acoustic modes, cuts, and stresses directions which would be used to determine the third-order elastic constants (TOEC), have been defined. BAW phase velocities as well as their pressure dependences in basic and rotated cuts of LiTaO3 crystal have been investigated experimentally.

The results of experimental studies on the propagation of bulk acoustic waves (10-200MHz) in a synthetic diamond single crystal under the influence of uniaxial pressure and temperature have been presented. Obtained data on second and third order elastic constants were used to calculate the anisotropy of the acoustic waves propagation characteristics in diamond under the pressure application. The peculiarities of wave propagation have been discussed.

Temperature coefficients of elastic constants (TC ij ) for trigonal and tetragonal crystals have been obtained. The TC ij of a number of trigonal and tetragonal crystals have been calculated and the comparison with known experimental data has been fulfilled. The nature of anomalous TC 66 of quartz has been discussed.

First, the Al/AlN/Al/Cr/diamond single crystal piezoelectric layered structure has been developed, and its properties have been investigated up to 8 GHz. The peculiarities associated with the influence of piezoelectric film on the Q factor of high overtones of substrate have been pointed out. High Q ∼ 104 has been found at 6–7 GHz band.