IEEE International Ultrasonics Symposium : [proceedings]

SUper-Resolution ultrasound imaging using Erythrocytes (SURE) creates microvascular images without any contrast agent injection, with only a few seconds of acquisition time. This paper hypothesizes that it is possible to reveal the microvascular density and velocity estimation of a human mole without the use of contrast agents, with just two seconds of data acquisition. In this study, imaging results from a single volunteer are presented. The SURE density image obtained using a Verasonics research scanner is compared with the Power Doppler image acquired from a commercial GE LOGIQ E9 scanner. The SURE tracking pipeline successfully visualized and estimated the velocity map and velocity profile of vessels as small as 65 mu m in diameter, with flow velocities as low as 3.2 mm/s. It shows the feasibility of visualizing the vasculature of benign moles, which potentially can assist medical doctors in distinguishing between benign and malignant moles and prioritizing them for further investigation.

Osseointegration is the main criterion for implantation success and remains a major challenge during implant development and patient treatment. Since conventional testing does not allow for accurate identification of implant loosening, we developed a new test stand where acoustic emission analysis is applied to the push-out testing process. This allows for more accurate data on implant loosening with similar loading conditions. This study investigates the interaction of mechanical behavior and acoustic emission (AE) characteristics of pork bone and sawbone samples during a combined push-out test. The primary aim is to analyze the AE data and correlate acoustic parameters. Therefore, 11 bone-implant samples of each material have been tested in a push-out process and analyzed with regards to the AE parameters. We conclude that identification of fracture types - shear or tensile - via rise angle and average frequency is a crucial step in the early detection of implant loosening. Although sawbone samples provide high reproducibility, they do not perfectly mimic natural bone, and animal bone offers more realistic results. Therefore, the proposed testing method is a promising tool for more accurate evaluation of bone-implant interactions in future osseointegrated samples.

Capacitive micromachined ultrasonic transducers (CMUTs) feature small size, wide bandwidth and good matching with acoustic impedance of water. The application of CMUTs in underwater sensing systems has the potential to reduce power consumption and save space. However, compared to traditional piezoelectric transducer, CMUTs exhibit lower sensitivity. To address this issue, this study designed a high-sensitivity CMUT device by reducing the silicon membrane thickness and optimizing the thickness of package material, and then characterized its acoustic performance. The results indicate that the CMUT exhibits significant advantages in terms of transmit sensitivity and bandwidth, and holds potential for applications in underwater sensing systems.

Cutaneous leishmaniasis (CL) is the most common form of leishmaniasis, manifesting as skin lesions that can lead to scarring and may have lifelong impacts on wellbeing. Early and accurate assessment of lesion biomechanics could enhance diagnosis and therapeutic monitoring. In this study, we evaluate the feasibility of four-dimensional (4D) dynamic optical coherence elastography (OCE) for in vivo characterization of CL lesions in murine model. Four mice at distinct disease stages: healthy baseline, day 1 post-infection, developed lesion, and post-treatment, were scanned. Volumetric elasticity values were obtained by calculating local elastic wave velocities. Healthy skin exhibited uniform wave propagation with an average Young's modulus of 19 +/- 2 kPa, and a similar value was observed at day 1 post-infection (20 +/- 5 kPa). In contrast, developed lesions displayed markedly increased stiffness (511 +/- 238 kPa), which decreased following treatment (68 +/- 27 kPa). These findings demonstrate that 4D dynamic OCE can quantitatively and non-invasively detect biomechanical changes associated with CL progression and treatment response, supporting its potential as a diagnostic and monitoring tool in clinical settings.

Intravascular ultrasound (IVUS) serves as an important imaging technique for the diagnosis of cardiovascular diseases (CVDs). Commercial IVUS catheters use either a side-looking rotating transducer or a circumferential transducer array to provide cross-sectional ultrasound (US) images. However, it cannot visualize the path ahead of the catheter, which is necessary for applications such as chronic total occlusion (CTO) angioplasty. This study proposes a concept dual-mode magnetic US catheter, mainly consisting of a magnetic component and two miniature high-frequency US transducers, which can perform both forward-looking sectorial scanning and side-looking circular scanning B-mode US imaging by remote magnetic actuation. The fabricated prototype catheter has an outer diameter of 1.8 mm. The center frequencies of the two transducers are both 30 MHz. Preliminary experiments are conducted to validate the effectiveness.

The logarithmic ratio of maternal to fetal spectral peak (LRSP) has been proposed as a potential biomarker for predicting preeclampsia (PEC) from umbilical vein Doppler signals. However, short clinical Doppler acquisitions limit spectral resolution and cause significant spectral leakage, degrading LRSP estimates from discrete Fourier transform (DFT)-based methods. Adaptive spectral estimation techniques, such as Capon and Amplitude and Phase Estimation (APES), theoretically offer improved resolution and robustness compared to DFT. This study compared adaptive spectral estimators with DFT using clinical Doppler data. Capon demonstrated the highest predictive performance (AUC = 0.75), higher than APES (AUC = 0.68) and DFT (AUC = 0.65), while also showing the smallest variance. These results suggest the potential utility of adaptive spectral estimation methods, particularly Capon, to improve the accuracy and robustness of LRSP-based preeclampsia prediction from short-duration Doppler signals in clinical practice.

Defect localization and sizing are critical for assessing the structural integrity of pipelines. This work presents simple and effective imaging-based techniques for localization and sizing of surface-breaking cracks on the outer walls of liquid-filled steel pipes. Given a small set of multimode ultrasound images of a pipe section under test, we use a novel tri-sectional sliding window to localize defect features in each image, followed by establishing correspondence among potentially differing location estimates. Our approach to subsequent crack sizing incorporates similarity-driven matching of localized image patches to synthetic templates. We demonstrate the effectiveness of the proposed methods using experimental data obtained from three pipe samples imaged with an immersed 256-element probe.

Ultrasound holography has emerged as a promising technique for non-invasive brain therapies, enabling precise targeting of specific regions. In this context, acoustic holograms can be generated using low-cost 3D-printed acoustic lenses, where the wavefront is encoded into the height of the pixels of a lens. Traditionally, holograms are designed to focus at a planar surface in front of the transducer, resulting in a hyperbolic phase profile under the thin lens approximation. However, when the physical lens thickness exceeds this approximation, aberrations occur. In this work, we propose a phase-matching approach that aligns the phase of the field produced at the exit of the lens with the target phase across a holographic volume. This method is validated through analytical and simulation techniques, demonstrating improved focusing performance compared to traditional methods.

Low-frequency sonophoresis has emerged as a minimally invasive alternative to hypodermic injection for transdermal drug delivery. Ultrasonic cavitation plays a pivotal role in enhancing skin permeability, with the ultrasonic transducer being a central component of this technique. Conventional horn-type transducers are often employed to generate low-frequency, high-intensity ultrasound. However, their bulky and heavy structure imposes substantial limitations for practical medical applications. Therefore, a compact low-frequency ultrasonic transducer capable of inducing cavitation on the skin surface has been designed and developed in this work to overcome these issues. The effect of the developed transducer on skin permeability was evaluated through in vitro sonophoresis experiments using fluorescein sodium as a model compound of low-molecular-weight drugs. The results showed that a 3-minute ultrasound treatment significantly enhanced transdermal permeation, achieving an 80-fold increase compared to the untreated samples. The temperature rise during sonication was limited to 7.1 degrees C, remaining well within the safety limits. These findings confirmed the potential of the developed compact transducer as a practical tool for safe and efficient sonophoresis-based transdermal drug delivery.

Ultrasound imaging is extensively used in medical diagnostics due to its non-invasive nature, real-time capability, and cost-effectiveness. Image reconstruction techniques need to be chosen between highly demanding methods (e.g. Capon adaptive technique) or faster low resolution limited algorithm (e.g. delay-and-sum). In this paper, this paper introduces the Reduced Rank Capon (RRC) method for fast ultrasound imaging reconstruction, which enhances DAS resolution while maintaining manageable computational complexity. RRC employs subspace decomposition to reduce the dimensionality of the beamforming process while preserving the key features of the Capon beam-former. By exploiting the dominant signal subspace, computed via the iterative OPAST algorithm, RRC reduces the complexity. Simulations and phantom experiments demonstrate RRC improves lateral resolution equivalently to Capon technique. RRC technique therefore emerges as a viable solution for real-time, high-quality ultrasound imaging, particularly advantagous in resource-constrained environments.

Anisakis larvae parasitizes several species of fishes. Ingesting raw seafood containing the parasite Anisakis can cause a serious disease called anisakiasis. Therefore, it is necessary to remove the parasites from fish before consumption. Conventional screening methods, such as the candling method, are easy to use for detecting surface parasites but lack the accuracy an d sensitivity to detect parasites embedded deep within fish muscle. To resolve these shortcomings, we devised a method using photoacoustic imaging. This imaging modality combines high tissue specificity with better penetration depth.We measured the photoacoustic spectra of Anisakis and fillets of fish such as mackerel. To investigate the ability to distinguish Anisakis from fish tissue using differences in the photoacoustic spectra, we calculated the intensity ratio of the photoacoustic signal. Our results showed that two specific wavelengths can be used to distinguish Anisakis from fish tissue, although the optimal wavelength combination may vary depending on the fish species. Furthermore, we constructed a photoacoustic imaging device based on this principle and demonstrated the ability to visualize Anisakis hidden in fillets.

Flexible transducers address the limitations of conventional rigid ultrasound probes for wearable applications, such as the continuous monitoring of vital organs. In this work, we demonstrate the first flexible micromachined ultrasound transducer array based on AlScN piezoelectric film. Using flat-panel display compatible technology which enables the manufacturing of large-aperture arrays we demonstrate a piezoelectric transducer with an active area of 1.5x1.5 cm2. The rigid glass substrate is removed and replaced by a flexible acoustic backing layer. Optimizations on thickness, mechanical rigidity, and acoustic properties of the backing material were performed to maximize the flexible transducer performance leading to transmit sensitivity of 3.8 kPa/V at 1.8 MHz and capable of acoustic imaging functionalities.

Accurate acoustic boundary conditions are essential for transient ultrasound simulations. Numerical schemes that rely on element-based discretization, such as finite volume methods (FVM), finite element methods (FEM), and discontinuous Galerkin (DG) methods, require definitions of both pressure and particle velocity components on the transducer surface. The spatial impulse response (SIR) method offers exact closed-form solutions for the velocity potential and pressure for canonical aperture geometries. However, existing formulations do not provide analytical descriptions of the lateral particle velocity components. To address this deficiency, a new closed-form expression for the lateral particle velocities produced by circular transducers is derived directly from the SIR. Validation through comparison with numerical spatial differentiation of the velocity potential shows excellent agreement. The new closed-form expression extends the applicability of the SIR method to the complete set of acoustic boundary quantities required for transient ultrasound simulations in element-based numerical solvers.

This paper introduces a novel single multifrequency complementary metal oxide semiconductor (CMOS) compatible piezoelectric micromachined ultrasound transducer (PMUT-on-CMOS), offering a compelling solution for ultrasound applications that demand high resolution and deep penetration. To address a trade-off between these parameters, a single PMUT with a dual-electrode configuration optimized for two distinct vibration modes is proposed. FEM simulation results provide the optimal dimensions to optimize mode 01 and mode 02 and the experimental results demonstrate simultaneous operation in liquid at 4 MHz and 16 MHz.

The controlled release of multiple drugs represents an exciting avenue that can be exploited for targeted therapies and for promoting tissue regeneration. In this context, perfluorocarbon droplets are promising ultrasound-responsive carriers, which can release their cargo upon acoustic droplet vaporization. In this study, we investigate the release behavior of two different droplet types, in response to low-frequency (38 kHz) and low-pressure (50-100 kPa) ultrasound. These two droplet formulations, consisting of the same perfluoropentane core but different shells (phospholipid, surfactant-based), are designed to respond to different US pressures. Therefore, they can be triggered separately by modulating the acoustic pressure, potentially enabling the ultrasound-controlled, temporally independent delivery of two drugs.

The nonlinear acoustic response of lipid-coated microbubbles (MBs) has been extensively employed in contrast-enhanced ultrasound applications. Although the harmonic and subharmonic behaviors of micron-sized MBs have been thoroughly studied, the acoustic response of commercially prevalent submicron contrast agents (<1 mu m) remains poorly understood. Interestingly, several experimental studies reported significantly higher contrast from submicron bubbles than predicted by linear scattering, which scales with the sixth power of radius. This work aims to elucidate the underlying physical mechanisms driving the high echogenicity observed in submicron agents.

In this paper, we present a semi-ring transducer based multimodal tomography platform integrating ultrasound tomography, ultrafast-ultrasound tomography, and multispectral photoacoustic tomography in a 256-element, 70 mm radius array. Using integrated imaging acquisition sequence, the system captures structural, hemodynamic, and molecular contrasts simultaneously with B-mode compounded frame rate up to 400 frames per second. The system is validated against a blood-flow mimicking phantom and demonstrates sub-500 mu m resolution and blood imaging sensitivity. In vivo human finger imaging show co-registered ultrasound anatomy, photoacoustic vascular maps, functional ultrasound flow images, and multispectral oxygenation mapping. Overall, this platform offers a powerful tomographic tool for comprehensive vascular diagnostics and functional assessment in both research and clinical settings.

This study proposes a novel film bulk acoustic resonator (FBAR) structure based on aluminum nitride (AlN), which enables lithographic tuning of the resonant frequency while preserving a high effective electromechanical coupling coefficient k(eff)(2) for the thickness extension (TE) mode. This design incorporates a periodic array of square units, each consisting of top and bottom platinum (Pt) electrodes and a sandwiched AlN layer, with circular holes etched into the top electrode. A quasi-TE mode is excited due to coupling of the primary TE mode and a lateral mode, induced by the periodic geometry, enabling enhanced vibration and tunable resonance. Simulation results reveal a frequency tuning range from 2.656 GHz to 2.822 GHz, achieved by adjusting the aperture ratio from 0.3 to 0.7. The proposed resonator attains an effective electromechanical coupling coefficient as high as 8.98%, comparable to that of conventional FBAR devices.

This work investigates the mechanical stability of periodically poled piezoelectric film (P3F) resonators at cryogenic temperatures. Lithium niobate P3F Lamb-mode resonators were experimentally characterized down to 13 K. Comparative measurements show that bilayer devices with identical per-layer thickness degrade below 93 K due to thermal stress, whereas trilayer devices exhibit a monotonic increase in quality factor (Q), reaching 720 at 13 K. The results highlight a unique advantage of the P3F platform: by increasing total film thickness, bending stiffness is enhanced, enabling robust operation across a wider cryogenic range. With further optimization, P3F devices demonstrate strong potential for ultra-low-temperature applications, including deep space exploration and quantum technologies.

Super-resolution ultrasound imaging (SRUI) is achieved by localising and tracking microbubble echoes in contrast enhanced ultrasound (CEUS). The resulting maps depict the imaged vascular structures. The objective of this work was to assess, in vivo, a new vascular-specific SRUI tracking algorithm incorporating criteria based on vascular characteristics. CEUS video data was collected from prostate cancer cases prior to radical prostatectomy (RP). After RP the specimen underwent macroscopic examination allowing comparison of features in SRUI maps with areas of malignancy and other prostate features. For 15 clinical cases, regions of known cancer, determined from RP pathology, were identified in the SRUI maps. In an initial subset of cases, 16 out of 17 known cancer regions were identified, with faster and higher volume blood flow, and generally wider vessel presentation. In addition to highlighting confirmed regions of cancer, patterns associated with benign prostatic hyperplasia, dilated glands and normal prostate structure such as peri-urethral blood vessels were identified. In conclusion the identification of vascular patterns associated with prostate disease is linked to multiple features that may formulate a multiparametric imaging biomarker.