Microbubble-mediated sonothrombolysis shows great potential for deep vein thrombosis (DVT) treatment, yet its clinical efficacy is often hindered by restricted drug penetration and suboptimal acoustic parameter configurations. While multi-ultrasound systems offer improved thrombolytic performance, acoustic field interactions remain poorly understood. This study developed a multiphysics simulation integrating microbubble dynamics, acoustic streaming, and convection-reaction to investigate the combined effects of an intravascular ultrasound catheter (IVUC) and a semi-flexible wearable ultrasound probe (sf-WUP). Numerical simulations were employed to predict the impact of dual-source configuration on thrombolysis, with validation performed through in vitro phantom experiments. Both approaches demonstrated that the dual-source approach achieves superior thrombolytic efficiency compared to either single mode. Furthermore, by introducing a pulse delay time (DT) between IVUC and sf-WUP, temporal decoupling of the two acoustic fields was achieved. Thrombolytic efficiency was found to increase with DT, exhibiting a negative correlation with temporal overlap between the two acoustic fields. The temporally decoupled dual-source configuration significantly outperformed synchronous excitation (DT = 0 ms). Specifically, in vitro experiments achieved a thrombolysis extent of 62.0% at DT of 3 ms, markedly higher than the 51.0% observed with synchronous excitation at DT = 0 ms. Simulations further revealed that temporal separation enhances acoustic streaming velocity, seepage flow, and clot deformation compared to synchronous excitation. These findings elucidate the crucial role of temporal decoupling in dual-source sonothrombolysis, providing a solid theoretical foundation for optimizing non-invasive therapeutic protocols.

Objective: Conventional medical imaging modalities (computed tomography, X-ray radiography, magnetic resonance imaging, and classical ultrasound imaging) exhibit inherent limitations in dynamic tissue monitoring. Although wearable ultrasound has addressed some of these shortcomings, existing solutions face significant challenges in achieving precise dynamic imaging during large-amplitude movements. This study develops a variable-angle ultrasound transducer (VA-US) and its imaging method to enable high-accuracy anatomical tracking under large-scale motion conditions. Methods: VA-US consists of two micro ultrasonic phased arrays connected by a sensible micro hinge, ensuring conformal contact with highly curved skin surfaces. Integrated magnetic induction sensor dynamically monitor spatial relationships of ultrasonic elements, guaranteeing accurate beamforming. Results: The capability of dynamic monitoring and real-time imaging of VA-US was verified by simulations, standard phantom and in-vivo experiments, showing potential applications in clinical diagnosis, rehabilitation and sport medicine. Conclusion: The proposed methodology is capable of capturing the dynamic anatomical changes of regions with significant cutaneous curvature variations. Significance: VA-US provides a novel approach for reflecting the health status of human tissues and organs under dynamic conditions, facilitating the monitoring and assessment of biomedical phenomena that are difficult to observe in static examinations.

Optical microscopy enables high-resolution visualization of biological structures but is fundamentally limited in vivo by strong scattering, restricting penetration to superficial depths. Photoacoustic microscopy (PAM) overcomes this optical diffusion barrier yet remains constrained by a depth-resolution trade-off: high-frequency transducer (HF-UT) provide fine detail but fails through heterogeneous tissues, whereas low-frequency transducer (LF-UT) penetrate deep but blurs structure. Breaking this limitation requires a new imaging strategy that decouples penetration from resolution. Here, we overcome this long-standing limitation by introducing a computational PA mesoscopy (CPAMe) framework built upon an LF-UT. A real-time hardware stabilization strategy—combining pulse-by-pulse laser-energy compensation with point-by-point encoder correction—ensures uniform, high-speed volumetric sampling. Building on multi-layer speed-of-sound modeling, we further developed a directionally weighted angular-spectrum synthetic-aperture focusing technique (DWAS-SAFT) that restores off-focus resolution and suppresses heterogeneity-induced artifacts using only a single volumetric scan. CPAMe markedly improves lateral resolution by 32.5% (from 673 to 454 µm), 40% (from 705 to 423 µm), and 46% (from 1368 to 733 µm) in tissue phantoms, through the mouse skull, and through human cranial repair PMMA, respectively. These capabilities enable high-resolution transcranial brain imaging, whole-body and molecular small-animal imaging, tumor visualization, and proof-of-concept human vascular imaging. Together, CPAMe provides a practical and scalable route to deep-tissue, high-resolution imaging, opening opportunities for non-invasive transcranial monitoring and advancing mesoscopy toward clinical translation.

Miniature ultrasound array transducers are the enabling technology for interventional imaging modalities such as intracardiac echocardiography (ICE) and endobronchial ultrasound (EBUS); yet their sub-millimeter element pitch forces the element width and thickness into comparable dimensions. In this regime, thickness and lateral vibration modes couple strongly, degrading device performance and invalidating the one-dimensional (1D) equivalent-circuit models routinely used in design. This paper develops a rapid, design-oriented analytical framework based on Lamb-wave theory that predicts the coupled resonance behavior of miniature array elements at negligible computational cost. Electrically excited vibration is modeled by the symmetric S0 Lamb mode of the piezoelectric plate, and its phase-velocity dispersion is mapped onto resonance-frequency trends and associated wave structures as functions of the width-to-thickness (w/t) ratio. The framework is validated on PZT-5H strips (0.167 mm thick, ~8 MHz) against finite-element simulations and impedance measurements. Near w/t = 1, where thickness and lateral modes are most strongly coupled, the model faithfully reproduces both the frequency trend and the evolving mode shapes. A physics-informed arctangent correction factor reduces the maximum theory–experiment error across the design ranges from ~17% to ~5%, and the method outperforms the conventional 1D model over 0.8 < w/t < 1.2. By delivering physically transparent, semi-analytical predictions at a fraction of the cost of finite-element analysis, this work provides a practical tool for detecting and suppressing thickness–lateral interference, with immediate relevance to the design of next-generation miniature array transducers.

Localization of the magnetic capsule endoscope is crucial to accurate actuation. Despite progress with internal magnetic field sensors and external magnetic sources, achieving reliable localization remains challenging in the presence of a time-varying internal magnetic field (IMF). This study proposes a compound localization method for an ultrasound capsule endoscope (USCE) based on an IMF sensor array and an external permanent magnet source. The method enables simultaneous 6-degrees of freedom (DOF) pose detection for closed-loop magnetic navigation and real-time ultrasound (US) beam scanning angle sensing for distortion-free US image reconstruction. First, a USCE consisting of an internal permanent magnet, a US transducer, Hall sensors, and an anchoring balloon is designed, enabling both spiral structure-based locomotion and high-quality endoluminal US imaging. Next, a compound localization strategy is presented, which realizes the separation of the time-varying IMF and external magnetic field, facilitating synchronous 6-DOF pose detection and scanning angle sensing. Furthermore, a closed-loop magnetic actuation method is proposed that allows automatic propelling in unknown tubular environments. Finally, the effectiveness of the presented method is validated through simulations, localization tests, imaging tests, and actuation tests. The demonstrated static pose detection error is 4.08 +/- 1.91 mm in position norm and 2.46 +/- 1.31 heading orientation, within a workspace shared with the robotic manipulator. In addition, the proposed scanning angle sensing successfully corrects US image distortion, providing subsurface structures for accurate diagnosis.

Interventional ultrasound imaging technology is widely utilized for the diagnosis of a diverse range of diseases. A slender interventional catheter is an essential component of such an apparatus. The combination of a universal main unit and multiple single-frequency catheters is the development trend of such instruments to meet the increasingly complicated clinical requirements. However, significant electromagnetic interference (EMI) would probably be generated during its operation, as the single-grounded catheter may exhibit characteristics similar to those of a monopole antenna. The critical clinical significance and specific usage scenarios render the electromagnetic compatibility safety concerns of this category of equipment indispensable. Meanwhile, the low signal-to-noise ratio (SNR) of high-frequency ultrasound makes any modulation of the electric insertion likely to affect the fragile acoustic echo signal and impact the image quality. Therefore, it remains a worthwhile pursuit to develop a general method that effectively suppresses electromagnetic radiation while preserving high-frequency ultrasonic signals for different frequencies in interventional scenarios. This paper proposes an electromagnetic radiation suppression technique for interventional ultrasound catheters based on impedance control methods. By designing an impedance matching network, the method achieves impedance matching within the working frequency band and intentional impedance mismatch in the non-operational frequency band of the catheter, thereby effectively suppressing electromagnetic emissions from catheters with different operating frequencies. Simulation and experimental results demonstrate that this approach not only significantly reduces the catheter’s radiated emissions to meet the CISPR11:2016 standard but also enhances the electro-acoustic conversion efficiency of the transducer and improves imaging quality in different ultrasound frequencies.

For interventional imaging devices, the magnetic-actuated approach holds great promise in enhancing catheter flexibility and improving imaging performance in complex environments, as exemplified in intravascular ultrasound (IVUS) and optical coherence tomography (OCT) systems. However, obtaining real-time pose estimation of the magnetic robot and compensating for nonuniform rotational distortion (NURD) in imaging remain critical challenges for clinical applications. This study proposes a solution to the aforementioned issues based on a miniaturized embedded magnetic field sensing module, which measures the resultant magnetic field from both the driving and the response magnets, and demonstrates the navigation mode of the magnetic-actuated IVUS (MIVUS) robot in a vascular model. In a permanent magnet space manipulated by the robotic arm, the position tracking error of the prototype robot is 3.34 +/- 1.74 mm, and the orientation error is 1.78 +/- 1.15 degrees . Furthermore, through front-end encoding, high-fidelity ultrasound (US) images with substantially suppressed NURD were reconstructed in tissue-mimicking phantoms. This study presents a synergistic magnetic navigation and imaging concept and provides preliminary validation.

Intravascular ultrasound (IVUS) is a critical imaging modality for the diagnosis of cardiovascular diseases (CVD). Conventional IVUS catheters primarily provide side-looking cross-sectional ultrasound (US) images to visualize the anatomy along the catheter path, leaving a blind zone distal to the catheter tip. This study develops a system capable of providing both forward- and side-looking IVUS within a single device. An active-steering catheter robot is designed, integrating dual miniaturized US transducers and an embedded magnetic element, selectively performing sector or circular ultrasonic beam scanning as driven by external magnetic fields. A sector scanning model based on Cosserat rod theory and a circular scanning model based on rotor dynamics are established to predict transducer motion. Tailored data acquisition strategies and a model-based phase-corrected synthetic aperture beamforming framework are developed to reconstruct high-quality images in both imaging modes. Experiments validate the accuracy of the proposed models and demonstrate effective dual-mode US imaging. The catheter robot achieves sector scanning with a maximum angle of 54.6° in the forward-looking mode and supports circular scanning at rotational speeds up to 1800 rpm. These capabilities demonstrate the feasibility of dual-perspective endoluminal imaging in benchtop phantom experiments, providing a technical basis for future systems.

This study focuses on overcoming the limitations of high-frequency array transducers, particularly their limited penetration depth resulting from weak transmitting energy. To address this issue, we propose a design strategy which can effectively suppress the sidelobe effects caused by the overwide aperture and ensure efficient acoustic energy transmission by increasing the element width based on dual sub-element structure. Finite element modeling (FEM) is conducted to analyze the influence of sub-element kerf on vibration modes, electrical impedance and acoustic field distribution, the radiating area, thereby optimizing the structure parameters. A 20 MHz linear array transducer with 128 elements was successfully fabricated based on the optimized parameters. Experimental results demonstrate that the transducer achieves a -6 dB bandwidth of 48%, lateral resolution better than 250 μm, axial resolution better than 100 μm, and imaging depth exceeding 5 cm. Vivo imaging experiments in small animals confirmed its practical applicability, which can capture the rapid beating of small animal heart in real time and perform high-sensitivity Doppler imaging of blood vessels. The obtained results suggest that the proposed sub-element based design strategy provides a feasible pathway for enhancing the performance of high-frequency linear arrays, offering promising potential for advanced small animal imaging applications.

Catheter-directed thrombolysis (CDT) is a commonly treatment for blood clots, but it requires large urokinase doses and carries bleeding risks. Therapeutic ultrasound has shown ability in enhancing thrombolysis, but existing ultrasound thrombolysis strategy is not suitable for long-term operation. This study had developed a semi-flexible wearable ultrasound probe (sf-WUP) to enhance effectiveness of CDT in heavy thrombus burden with low-dose urokinase. The sf-WUP was bent to focus on the thrombus and transmit either single-frequency ultrasound at 1.8 MHz or dual-frequency ultrasound (1.8 MHz and 1.88 MHz). The catheter was used to deliver low-dose urokinase or a combination of urokinase and microbubbles to the target thrombus. Thrombolysis extent was the thrombus mass reduction percentage. In 50 min, the thrombolysis extent of low-dose urokinase was only 11.40%, while the sf-WUP using single-frequency ultrasound with microbubbles increased to 55.23%. Under constant acoustic power, the dual-frequency ultrasound reached a thrombolysis extent of 63.78%. When the peak-to-peak sound pressure was kept constant, the dual-frequency ultrasound achieved a similar thrombolysis extent but with 9.75%-13.84% lower electrical power compared to single-frequency ultrasound. The sf-WUP using single-frequency ultrasound can significantly improve the thrombolysis extent of low-dose urokinase CDT. The use of dual-frequency ultrasound with constant power can further enhance efficiency, while dual-frequency ultrasound with constant peak-to-peak sound pressure shows better energy efficiency. Both are compatible with wearable devices, laying the foundation for the clinical translation of ultrasound assisted CDT.

Shear Wave Elastography (SWE) is an imaging technique that detects shear waves generated by tissue excited by Acoustic Radiation Force (ARF), and characterizes the mechanical properties of soft tissue by analyzing the propagation velocity of shear wave. ARF induces a change in energy density through the nonlinear propagation of ultrasound waves, which drives the tissue to generate shear waves. However, the amplitude of shear waves generated by ARF is weak, and the shear waves are strongly attenuated in vivo. Furthermore, the shear waves are usually drowned out by noise at deep locations, which presents a challenge in the detection of shear waves and low signal-to-noise ratios. In this paper, we investigate the feasibility of applying the Chirp coded signal for shear wave excitation (Chirp-SWE) in ARF-based shear wave elastography. The use of Chirp coded excitation of push waveforms was employed to enhance the action of ARF, thereby effectively exciting shear waves. Comparative experiments were carried out with conventional sine long pulses (SWE) and the Barker coded signal (Barker-SWE). The analysis of theoretical and simulation results revealed that Chirp-SWE could increase the excitation energy by approximately 10% compared to conventional SWE and Barker-SWE. The results of the elastic phantom experiments demonstrated that the average peak axial particle velocity obtained by Chirp-SWE was approximately 30%-50% higher, which facilitated the formation of a more stable shear wave. Additionally, it exhibited a higher signal-to-noise ratio during elasticity measurements. The in vitro liver experiments further validated the feasibility of implementing Chirp-SWE in tissues. The results demonstrated the feasibility and advantages of Chirp coded excitation of push waveforms in improving shear wave elastography results. It is expected that this will enhance the accuracy and robustness of soft tissue elastography.

BACKGROUND:Diagnosing and characterizing breast lesions and tumors remains a common challenge in clinical practice. Ultrasound imaging stands out for its safety, real-time capability, and affordability. However, the image quality of conventional ultrasound examination is limited, and the diagnosis of ultrasonographic images depends heavily on the experience of the sonographer. Therefore, improving ultrasound images and extracting tissue information from ultrasound signals to provide auxiliary means is crucial for accurate breast tumor diagnosis. PURPOSE:Medical ultrasound imaging has been widely used in clinical diagnosis. However, traditional ultrasound has limitations in the diagnosis of breast soft tissue diseases. This study proposed a high scattering sensitivity fuzzy entropy (FE) imaging method to enhance image contrast and improve detectability for breast tumors. Moreover, this imaging method can make a preliminary classification and characterization of benign and malignant breast lesions through quantitative analysis of ultrasound radio frequency data and the calculation of the entropy value without biopsy examination. METHODS:To achieve the fuzzy entropy imaging, a sliding window is selected to traverse across the image with a step of one sampling point while the entropy value within the sliding window is calculated. This entropy value is assigned to the center pixel of the window. The parametric image was obtained after the entropy values of all pixels were calculated. During the clinical experiments, the breast lesions were classified as benign or malignant by biopsy examination. After entropy imaging, the average entropy value of the lesion area was calculated. The entropy values of all cases of benign and malignant tumors were averaged, respectively, to verify whether the fuzzy entropy can characterize the breast lesions. All the statistical analysis was conducted by one-sample t-test to obtain the mean value and standard deviation. The Tukey test was performed, and the effect size of Cohen's d was calculated to verify whether there was a significant difference between the entropy value of benign lesions and malignant lesions. RESULTS:In the clinical breast imaging experiment, the FE method obtained the highest Matthews correlation coefficient (MCC) of 0.875 ± 0.047 (p < 0.0001) and F1 score of 0.876 ± 0.049 (p < 0.0001). The MCC and F1 scores of FE imaging were significantly different from those of other entropy imaging methods in the Tukey test (p < 0.0001). The effect sizes of Cohen's d of F1 score of FE method compared with the WSE method and hNSE method were 1.498 and 1.107, respectively. The contrast-to-noise ratio (CNR) of FE images increased by 124.37% (p < 0.0001) compared with B-mode images (5.210 ± 3.136, p < 0.0001). The above results show that the FE method has good comprehensive performance in improving the detection accuracy and contrast of breast lesions. The fuzzy entropy value of benign tumors (0.033 ± 0.0.14, p < 0.0001) is higher than that of malignant tumors (0.022 ± 0.013, p < 0.0001) with both statistical and practical significance, indicating that the benign and malignant tumors can be characterized and classified by fuzzy entropy value. CONCLUSIONS:The proposed ultrasound fuzzy entropy breast imaging method can effectively improve the ultrasound imaging performance and the ability to detect lesions, because fuzzy entropy can measure the microscopic chaos of breast tissue and enhance the scattering information characteristics in the signal. Meanwhile, fuzzy entropy imaging can classify benign and malignant lesions, because fuzzy entropy considers the causality within the ultrasound signal, avoiding information aliasing and loss, so that it can detect weaker information in the signal and can reflect organizational information more accurately.

Stimulated Raman scattering(SRS)-based multi-wavelength optical-resolution photoacoustic microscopy(MW-OR-PAM)enables high-speed functional imaging in vivo by providing rich molecular contrast.However,its broader biomedical application remains limited by the reduced hemoglobin absorption beyond 600 nm and the insufficient sensitivity of existing microscope probes.Here,we address these challenges through two key innovations.First,we develop a high-sensitivity acoustic-optical probe tailored for the SRS-based MW-OR-PAM system.The probe integrates a 9-μm-thick P(VDF-TrFE)film-based transducer between a planoconvex lens and a large-aperture acoustic lens,achieving a broad bandwidth(98.94％),a high numerical aperture(0.67),and adjustable optical focusing.Second,we introduce tartrazine,a biocompatible and tissue-transparent dye,to induce reversible optical clearing in vivo,thereby enhancing light penetration at wavelengths above 600 nm.These advances significantly improve microvascular imaging at longer wavelengths.We validate the performance of our system through high-resolution imaging of skin microvasculature,oxygen saturation mapping,and transcranial brain imaging.Our results establish MW-OR-PAM as a versatile and robust platform for functional and pathological imaging,effectively extending the spectral and penetration depth limitations of conventional OR-PAM systems in the red spectral region.

The effective radiating area is a crucial parameter in ultrasound applications, particularly for evaluating the therapeutic effect of planar non-focused therapeutic ultrasound transducers. Recent studies, however, reveal significant uncertainty in measuring effective radiating area. Additionally, the high-power input used in the measurement may shorten the lifespan of both the transducer and the hydrophone. These issues undermine the reliability of the effective radiating area measurement results. At present, a definitive and practical method for obtaining a reliable measurement of the effective radiating area safely and conveniently is still lacking. To address these issues, the measurement setup, including the duty cycle, grid accuracy, and hydrophone sensitivity, was discussed in detail in this study. The duty cycles were classified into low-level and high-level categories in consideration of the specific requirements and limitations of the actual experimental setup. The trends revealed by the ideal-field simulation with different grid sizes, in relation to the duty cycles, indicated that the calculated effective radiating area fluctuated within a narrow range, which was far smaller than that specified by the IEC 61689 standard (20%). When the low duty cycles were utilized, the acoustic absorber was omitted. Experimental measurements on a customized ultrasound transducer confirmed that the effective radiating area under high duty cycles can be reliably predicted from that under low duty cycles, with an error range less than 7%. Furthermore, an example is presented to further investigate the predication stability and reliability when different hydrophones are applied to measure the treatment head of a physiotherapy product.

Quantitative ultrasound (QUS) is a technique that extracts tissue features from radiofrequency (RF) signals or envelope data. It can reflect cartilage surface and depth information related to osteoarthritis (OA), such as proteoglycans (PG) content, shallow cartilage cell spacing, and cartilage thickness. However, the QUS results of current relevant studies lack detailed information and poor visualization, which is not conducive to the accurate diagnosis of cartilage injury by clinicians. A 3D visualization method for quantitative evaluation of knee cartilage lesions based on high-frequency ultrasound was developed. C-Scan was performed on human advanced knee arthritis specimens using a 30MHz single-element ultrasonic probe. Then, QUS results were calculated and the 3D ultrasonic model was established. Finally, the results of QUS are rendered by color on the upper surface of the 3D ultrasonic model. According to the results, the method can distinguish the cartilage injury intuitively and effectively.

Intraosseous ultrasound imaging is valuable for guiding pedicle screw placement in surgery. However, single-frequency ultrasound, whether low or high, often fails to provide both adequate imaging resolution and depth simultaneously. To address this limitation, we introduce a novel ultrafast multi-frequency ultrasound patch fusion imaging method for pedicle screw navigation. This approach combines the strengths of both high-frequency and low-frequency ultrasound images, greatly enhancing the detail and clarity of the resulting images while significantly reducing the time required for image fusion. We validated our method through simulation and ex-vivo experiments, using metrics such as Information Entropy (IE), Spatial Frequency (SF), and Average Gradient (AG) to assess the quality of the fused images. We also recorded the algorithm’s execution time. The results demonstrate that our fusion method substantially improves image richness and clarity, enabling a more comprehensive and accurate assessment of the pedicle screw track. Importantly, it also reduces fusion time compared to previous methods, making real-time clinical multi-frequency ultrasound fusion imaging a viable possibility. The in-vivo experimental results of the sheep spinal pedicle screw track further demonstrate the capabilities of the patch fusion method in visualizing the internal conditions of the pedicle screw track and meeting the requirements for real-time fusion imaging. The proposed approach offers substantial support in surgical real-time navigation and ongoing monitoring within the domains of orthopedics and surgery.

Ultrasound blood flow imaging plays a crucial role in the diagnosis of cardiovascular and cerebrovascular diseases. Conventional ultrafast ultrasound plane-wave imaging techniques have limited capabilities in microvascular imaging. To enhance the quality of blood flow imaging, this study proposes a microbubble-based H-Scan ultrasound imaging technique. This technique utilizes high-order H-Scan to detect the Rayleigh scattering contributed by blood flow and microbubbles at certain concentrations. The detected results are then processed in the B channel using methods such as clutter filtering based on Casorati matrix singular value decomposition (Casorati-SVD). Compared with the control group without H-Scan, the signal-to-noise ratio (SNR) of the experimental group using the microbubble-based H-Scan ultrasound imaging technique was increased by 38.61% on average and the contrast signal-to-noise ratio (CNR) was increased by 39.5% on average. The improved image quality of microvascular flow imaging was visibly enhanced. This method demonstrates significant advantages in enhancing the sensitivity and accuracy of ultrasound blood flow imaging, indicating considerable potential for clinical applications.

This research focuses on the challenge of balancing signal integrity and high-voltage tolerance in the front-end protection circuits of high-frequency ultrasound imaging systems. To overcome the limitations of traditional protection schemes-such as high insertion loss, significant harmonic distortion, and limited response speed-a novel circuit architecture based on a high-voltage analog multiplexer switch is proposed. Comparative tests show that the proposed structure achieves an insertion loss of only $\mathbf{- 1. 6 9 d B}$ at $\mathbf{1 0 0 M H z}$, outperforming conventional schemes (which range from −2.26 $\mathbf{d B}$ to $\mathbf{- 4. 1 6 d B}$). It also exhibits significantly lower total harmonic distortion across the full frequency band and dynamic range, alongside better clamping characteristics and a faster response speed. To address the blind zone caused by the finite switch transition time, a delayed emission synchronization control method is introduced. This method sets the high-voltage excitation pulse output during the mid-to-late phase of the switching transition, compressing the blind zone and improving near-field detection capability. The results verify that the proposed circuit provides good signal fidelity, high-voltage suppression, and adaptability for high-precision ultrasonic imaging, offering an effective solution for high-performance ultrasonic front-end design.