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Ultrasound (US) shear wave elasticity imaging (SWEI) is a mature technique for diagnosing the elasticity of isotropic tissues. However, the elasticity of anisotropic tissues, such as muscle and tendon, cannot be diagnosed correctly using SWEI because the shear wave velocity (SWV) varies with tissue fiber orientations. Recently, SWEI has been studied for measuring the anisotropic properties of muscles by rotating the transducer; however, this is difficult for clinical practice.In this study, a novel dual-direction shear wave imaging (DDSWI) technique was proposed for visualizing the mechanical anisotropy of muscles without rotation. Longitudinal and transverse shear waves were created by a specially designed external vibrator and supersonic pushing beam, respectively; the SWVs were then tracked using ultrafast US imaging. Subsequently, the SWV maps of two directions were obtained at the same scanning cross section, and the mechanical anisotropy was represented as the ratio between them at each pixel.The performance of DDSWI was verified using a standard phantom, and human experiments were performed on the gastrocnemius and biceps brachii. Experimental results of phantom revealed DDSWI exhibited a high precision of0.81% and a low bias of3.88% in SWV measurements. The distribution of anisotropic properties in muscle was visualized with the anisotropic ratios of 1.54 and 2.27 for the gastrocnemius and biceps brachii, respectively.The results highlight the potential of this novel anisotropic imaging in clinical applications because the conditions of musculoskeletal fiber orientation can be easily and accurately evaluated in real time by DDSWI.

Neovascularization of injured tendons prolongs the proliferative phase of healing, but prolonged neovascularization may cause improper healing and pain. Currently, ultrasound Doppler imaging is used for measuring the neovascularization of injured tendons (e.g., Achilles tendon). However, the resolution of state-of-the-art clinical ultrasound machines is insufficient for visualizing the neovascularization in finger tendons. In this study, a high-frequency micro-Doppler imaging (HFμDI) based on 40-MHz ultrafast ultrasound imaging was proposed for visualizing the neovascularization in injured finger tendons during multiple rehabilitation phases.The vessel visibility was enhanced through a block-wise singular value decomposition filter and several curvilinear structure enhancement strategies, including the bowler-hat transform and Hessian-based vessel enhancement filtering. HFμDI was verified through small animal kidney and spleen imaging because the related vessel structure patterns of mice are well studied. Five patients with finger tendon injuries underwent HFμDI examination at various rehabilitation phases after surgery (weeks 11-56), and finger function evaluations were performed for comparisons.The results of small animal experiments revealed that the proposed HFμDI provides excellent microvasculature imaging performance; the contrast-to-noise ratio of HFμDI was approximately 15 dB higher than that of the conventional singular value decomposition filter, and the minimum detectable vessel size for mouse kidney was 35 μm without the use of contrast agent. In the human study, neovascularization was clearly observed in injured finger tendons during the early phase of healing (weeks 11-21), but it regressed from week 52 to 56. Finger rehabilitation appears to help reduce neovascularization; neovascular density decreased by approximately 1.8%-8.0% in participants after 4 weeks of rehabilitation.The experimental results verified the performance of HFμDI for microvasculature imaging and its potential for injured finger tendon evaluations.

Ultrafast ultrasound imaging based on plane wave (PW) compounding has been proposed for use in various clinical and preclinical applications, including shear wave imaging and super resolution blood flow imaging. Because the image quality afforded by PW imaging is highly dependent on the number of PW angles used for compounding, a tradeoff between image quality and frame rate occurs. In the present study, a convolutional neural network (CNN) beamformer based on a combination of the GoogLeNet and U-Net architectures was developed to replace the conventional delay-and-sum (DAS) algorithm to obtain high-quality images at a high frame rate. RF channel data are used as the inputs for the CNN beamformers. The outputs are in-phase and quadrature data. Simulations and phantom experiments revealed that the images predicted by the CNN beamformers had higher resolution and contrast than those predicted by conventional single-angle PW imaging with the DAS approach. In in vivo studies, the contrast-to-noise ratios (CNRs) of carotid artery images predicted by the CNN beamformers using three or five PWs as ground truths were approximately 12 dB in the transverse view, considerably higher than the CNR obtained using the DAS beamformer (3.9 dB). Most tissue speckle information was retained in the in vivo images produced by the CNN beamformers. In conclusion, only a single PW at 0° was fired, but the quality of the output image was proximal to that of an image generated using three or five PW angles. In other words, the quality-frame rate tradeoff of coherence compounding could be mitigated through the use of the proposed CNN for beamforming.

Objective: Estimating the elasticity distribution in the cornea is important because corneal elasticity is usually influenced by corneal pathologies and surgical treatments, especially for early corneal sclerosis. Because the thickness of the cornea is typically less than 1 mm, high-resolution ultrasound elastography as well as the Lamb wave model is required for viscoelastic property estimation. In the present study, an array high-frequency ultrasound (HFUS) elastography method based on ultrafast ultrasound imaging was proposed for estimating the viscoelastic properties of porcine cornea. Methods: The elastic wave was generated by an external vibrator, after which the wave propagation image was obtained using a 40-MHz array transducer. Viscoelasticity estimation was performed by fitting the phase velocity curve using the Lamb wave model. The performance of the proposed HFUS elastography system was verified using 2-mm-thick thin-layer gelatin phantoms with gelatin concentrations of 7% and 12%. Ex vivo experiments were carried out using fresh porcine cornea with artificial sclerosing. Results: Experimental results showed that the estimated elasticity was close to the standard value obtained in the phantom study when the Lamb wave model was used for elasticity measurement. However, the error between the standard elasticity values and the elasticity values estimated using group shear wave velocity was large. In the ex vivo eyeball experiments, the estimated elasticities and viscosities were respectively 9.1 ± 1.3 kPa and 0.5 ± 0.10 Pa·s for a healthy cornea and respectively 15.9 ± 2.1 kPa and 1.1 ± 0.12 Pa·s for a cornea with artificial sclerosis. A 3D HFUS elastography was also obtained for distinguishing the region of sclerosis in the cornea. Conclusion: The experimental results demonstrated that the proposed HFUS elastography method has high potential for the clinical diagnosis of corneal diseases compared with other HFUS single-element transducer elastography systems.

Low-intensity transcranial focused ultrasound (tFUS) has gained considerable attention as a promising noninvasive neuromodulatory technique for human brains. However, the complex morphology of the skull hinders scholars from precisely predicting the acoustic energy transmitted and the region of the brain impacted during the sonication. This is due to the fact that different ultrasound frequencies and skull morphology variations greatly affect wave propagation through the skull.Although the acoustic properties of human skull have been studied for tFUS applications, such as tumor ablation using a multielement phased array, there is no consensus about how to choose a single-element focused ultrasound (FUS) transducer with a suitable frequency for neuromodulation. There are interests in exploring the magnitude and dimension of tFUS beam through human parietal bone for modulating specific brain lobes. Herein, we aim to investigate the wave propagation of tFUS on human skulls to understand and address the concerns above.Both experimental measurements and numerical modeling were conducted to investigate the transmission efficiency and beam pattern of tFUS on five human skulls (C3 and C4 regions) using single-element FUS transducers with six different frequencies (150-1500 kHz). The degassed skull was placed in a water tank, and a calibrated hydrophone was utilized to measure acoustic pressure past it. The cranial computed tomography scan data of each skull were obtained to derive a high-resolution acoustic model (grid point spacing: 0.25 mm) in simulations. Meanwhile, we modified the power-law exponent of acoustic attenuation coefficient to validate numerical modeling and enabled it to be served as a prediction tool, based on the experimental measurements.The transmission efficiency and -6 dB beamwidth were evaluated and compared for various frequencies. An exponential decrease in transmission efficiency and a logarithmic decrease of -6 dB beamwidth with an increase in ultrasound frequency were observed. It is found that a750 kHz ultrasound leads to a relatively lower tFUS transmission efficiency (5%), whereas a350 kHz ultrasound contributes to a relatively broader beamwidth (5 mm). Based on these observations, we further analyzed the dependence of tFUS wave propagation on FUS transducer aperture size.We successfully studied tFUS wave propagation through human skulls at different frequencies experimentally and numerically. The findings have important implications to predict tFUS wave propagation for ultrasound neuromodulation in clinical applications, and guide researchers to develop advanced ultrasound transducers as neural interfaces.

Tendon injuries lead to tendon stiffness, which impairs skeletal muscle movement. Most studies have focused on patellar or Achilles tendons by using ultrasound elastography. Only a few studies have measured the stiffness of hand tendons because their thickness is only 1–2 mm, rendering clinical ultrasound elastography unsuitable for mapping hand tendon stiffness. In this study, a high-frequency ultrasound shear elastography (HFUSE) system was proposed to map the shear wave velocity (SWV) of hand flexor tendons. A handheld vibration system that was coaxially mounted with an external vibrator on a high-frequency ultrasound (HFUS) array transducer allowed the operators to scan hand tendons freely. To quantify the performance of HFUSE, six parameters were comprehensively measured from homogeneous, two-sided, and three-sided gelatin phantom experiments: bias, precision, lateral resolution, contrast, contrast-to-noise ratio (CNR), and accuracy. HFUSE demonstrated an excellent resolution of $147~\mu \text{m}$ to distinguish the local stiffness of thin phantom (thickness: 1.2 mm) without compromising bias, precision, contrast, CNR, and accuracy, which has been noted with previous systems. Human experiments involved four patients with hand tendon injuries who underwent ≥2 months of rehabilitation. Using HFUSE, two-dimensional SWV images of flexor tendons could be clearly mapped for healthy and injured tendons, respectively. The findings demonstrate that HFUSE can be a promising tool for evaluating the elastic properties of the injured hand tendon after surgery and during rehabilitation and thus help monitor progress.

Purpose To increase patient safety, ultrasound detection acupuncture (UDA) has been developed, which can detect a safe depth for acupuncturists to avoid causing pneumothorax. This study aims to develop and evaluate a single-transducer ultrasound for acupuncture (UFA) to promote UDA. Methods Special A-mode and M-mode signals were analyzed to identify the depth of the lung. Six subjects were recruited to test the reliability and validity of UFA on GB21, LV14 and BL43 acupuncture points. Results The result showed UFA’s coefficient of variation was less than 0.2 and no difference in age, gender, and BMI of the subjects statistically, demonstrating excellent reliability. However, the content validity index of 0.51 did not meet expectations. UFA has good reliability, but it cannot reach the level of medical ultrasound. UFA uses A-mode and the seashore sign of M-mode to make a good identification of the lung, and it would be useful in the promotion of UDA.

Thromboembolism in vessels often leads to stroke or heart attack and even sudden death unless brought under control. Sonothrombolysis based on ultrasound contrast agents has shown promising outcome in effective treatment of thromboembolism. Intravascular sonothrombolysis transducer was reported recently for unprecedented sonothrombolysis in vitro. However, it is necessary to provide an imaging guide during thrombolysis in clinical applications for optimal treatment efficiency. In this paper, a dual mode ultrasound catheter was developed combining a 16 MHz high frequency element (imaging transducer) and a 220 kHz low frequency element (treatment transducer) for sonothrombolysis in vitro. The treatment transducer was designed with a 20 layer PZT-5A stack with aperture size of 1.2 × 1.2 mm(2) and the imaging transducer with the aperture size of 1.2 × 1.2 mm(2) was attached in front of the treatment transducer. Both transducers were assembled into a customized two-lumen 10 Fr catheter. In vitro experiment was carried out using bovine blood clot. Imaging tests were conducted showing that the backscattering signals can be obtained with a high signal-to-noise (SNR) ratio for the 16 MHz imaging transducer. Sonothrombolysis was performed successfully that the volume of clot was reduced significantly after the 30 min of treatment. The size changes of clot were observed clearly using the 16 MHz M-mode imaging during the thrombolysis. The findings suggest that the proposed ultrasound-guided intravascular sonothrombolysis can be enhanced since the position of treatment transducer can be adjusted with the target at the clot due to the imaging guide.

Zebrafish is a well-established animal model for developmental and disease studies. Its optical transparency at early developmental stages allows in vivo tissues visualization. Interaction of polarized light with these tissues provides information on their structure and properties. This approach is effective for muscle tissue analysis due to its birefringence. To enable real-time Mueller-matrix characterization of unanesthetized fish, we assembled a microscope for single-shot Mueller-matrix imaging. First, we performed a continuous observation of 48 species within the period of 2 to 96 hpf and measured temporal dependencies of the polarization features in different tissues. These measurements show that hatching was accompanied by a sharp change in the angle and degree of linearly polarized light after interaction with muscles. Second, we analyzed nine species with skeletal disorders and demonstrated that the spatial distribution of light depolarization features clearly indicated them. Obtained results demonstrated that real-time Mueller-matrix imaging is a powerful tool for label-free monitoring zebrafish embryos.

Chronic wounds have negative physical and psychological effects on patients and increase the health care burden. Consequently, chronic wound in the elderly population is an important issue. Ultrasound can be a great modality for treating chronic wounds because of its noninvasive and safety characteristics; it can accelerate in vitro and in vivo wound healing. In this study, we developed a novel noncontact ultrasound for wound treatment. We stimulated human epidermal keratinocyte migration using low-intensity pulsed ultrasound (LIPUS) with a noncontact transducer to avoid direct contact with the wound. We also compared the effects of 15-min contact and noncontact transducer stimulation, where a 1-MHz contact transducer (intensity = 40 or 200 mW/cm

Objective: Injuries to the hands, wrists, and fingers often involve damage to the tendons. The ability to measure tendon movements during the rehabilitation process can provide clinicians with important information in the quantification of tendon injuries. Conventionally, the tendon is considered a single spring-like structure during force transmission, and its twisted structure is neglected. Recently, clinicians believed that the twisted fiber structure (which enables tendon rotation during movement) of the tendon can provide it with a degree of elasticity and improve the efficiency of force transmission. However, observation of the hand tendon rotation in vivo by using the current imaging modalities is difficult. Methods: In this study, a 40-MHz high-frequency vector Doppler imaging (HFVDI) was used to visualize the movement of the hand tendon during muscle contraction. The performance of HFVDI was verified using a rotation phantom experiment. Two human experiments were designed in the present study: 1) participants were allowed to bend their distal and proximal interphalangeal (DIP and PIP) joints of fingers freely and 2) the PIP joint of the finger was fixed such that only the DIP could be moved. The HFVDIs of the flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) tendons were obtained in the transverse and longitudinal views to observe the movements of the hand tendon during finger movements. Results: The average longitudinal displacements of the FDS and FDP were approximately 3–4 mm for free bending of the finger; however, it was reduced when only the DIP was moved. The rotational phenomenon of the FDS and FDP tendons was observed in the transverse view, which demonstrated the different rotational behaviors of the FDS and FDP fibers during muscle contraction. Conclusion: All the results validated the potential of HFVDI as a novel tool for visualizing tendon rotation and would be useful in providing quantitative information regarding tendon function to determine the rehabilitation process following injuries.

Obstructive sleep apnea (OSA) is a chronic breathing disorder characterized by intermittent sleep state-dependent upper airway (UA) collapse. The tongue comprises the primary UA dilator muscle and plays an essential role in the pathogenesis of OSA. We examined whether tongue stiffness measurement using ultrasound (US) shear wave elastography (SWE) is useful for predicting the existence of OSA. Forty-six participants (20 healthy controls and 26 patients with OSA) underwent transcutaneous submental SWE using a US system. Quantification with a shear modulus of 0-200 kPa was recorded during normal breathing and Muller's maneuver (MM). Polysomnography was used as the reference standard. Mid-sagittal tongue stiffness was significantly higher in awake patients with OSA than in controls during normal breathing and the MM (p < 0.0001). The posterior third of the tongue in patients with OSA had the highest value of shear modulus during the MM (p < 0.001). With cut-offs of 27.6 and 35.2 kPa for the whole tongue and posterior third during the MM, respectively, the sensitivity obtained was 69.2% and 76.9%, and the specificity was 85% and 95%, respectively, for detecting OSA. The corresponding areas under the receiver operating characteristic curve were 0.82 and 0.88, respectively. US SWE may have the potential for non-invasive tongue stiffness measurement in OSA.

In this article, we present a high delay resolution and all-digital transmit-beamforming circuit for use in high-frequency and wearable ultrasound imaging systems. The proposed transmit beamformer comprises an all-digital delay-locked loop (ADDLL), a cycle-based beamforming delay line (CBDL), and a pulse controller. ADDLL can provide specific digital control code for the CBDL to generate stable and suitable delays to excite array transducer elements without variations in process, voltage, and temperature. CBDL not only provides a finer delay resolution for high-frequency ultrasound imaging systems but also requires a few delay cells to maintain the duty cycle of long prorogation signals, thereby significantly reducing hardware costs. The pulse controller can adjust the number and width of output pulses to meet the requirements of different ultrasonic transducers and Doppler ultrasound color imaging. The proposed transmit beamformer uses a 0.18- $\mu \text{m}$ CMOS technology for a 30-MHz high-frequency linear array with 256 elements, and the focusing depth is from 3.5 to 8.1 mm. The measurement results indicate that the proposed transmit-beamforming design can achieve a maximum time delay of 562.6 ns with an average time resolution of 535 ps. The proposed design offers a smaller volume and finer delay resolution, and it is highly suitable for wearable ultrasound imaging systems.

BACKGROUND: The adult human heart cannot efficiently generate new cardiac muscle cells in response to injury, and, therefore, cardiac injury results in irreversible damage to cardiac functions. The zebrafish (Danio rerio) is a crucial animal model in cardiac research because of its remarkable capacity for tissue regeneration. An adult zebrafish can completely regenerate cardiac tissue without a scar being formed, even after 20% of its ventricular myocardium has been resected. Zebrafish have been utilized in developmental biology and genetics research; however, the details of myocardium motions during their cardiac cycle in different regeneration phases are still not fully understood. METHODS: In this study, we used a 70-MHz high-resolution ultrasound deformation imaging system to observe the functional recovery of zebrafish hearts after amputation of the ventricular apex. RESULTS: The myocardial deformation and cardiac output (CO) were measured in different regeneration phases relative to the day of amputation. In response to the damage to the heart, the peak systolic strain (ε(max)) and strain during ejection time (ε(ej)) were lower than normal at 3 days after the myocardium amputation. The CO had normalized to the baseline values at 7 days after surgery. CONCLUSIONS: Our results confirm that the imaging system constructed for this study is suitable for examining zebrafish cardiac functions during heart regeneration.

Scars are a type of fibrous tissue that typically forms during the wound healing process to replace damaged skin. Because studies have indicated a high correlation between scar stiffness and clinical symptoms, assessing the mechanical properties of scar is crucial for determining an appropriate treatment strategy and evaluating the treatment's efficacy. Shear wave elastography (SWE) is a common technique for measuring tissue elasticity. Because scars are typically a few millimeters thick, they are thin-layer tissues, and therefore, the dispersion effect must be considered to accurately estimate their elasticity. In this study, high-frequency ultrasound (HFUS) elastography was proposed for estimating the elastic properties of scars by using the Lamb wave model (LWM). An external vibrator was used to generate elastic waves in scar tissue and skin, and the propagation of the elastic waves was tracked through 40-MHz ultrafast ultrasound imaging. The elasticity was estimated through shear wave models (SWMs) and LWMs. The effectiveness of using HFUS elastography was verified through phantom and human studies. The phantom experiments involved bulk phantoms with gelatin concentrations of 7% and 15% and 2-4-mm-thick thin-layer 15% gelatin phantoms. The studies of three patients with eight cases of scarring were also conducted. The phantom experimental results demonstrated that the elasticity estimation biases for the thin-layer mediums were approximately -36% to -50% and 3% to -9% in the SWMs and LWMs, respectively, and the estimated shear moduli were 12.8 ± 5.4 kPa and 74.8 ± 26.8 kPa for healthy skin and scar tissue, respectively. All the results demonstrated that the proposed HFUS elastography has a great potential for improving the accuracy of elasticity estimations in clinical dermatological diagnoses.

High-frequency ultrasound (HFUS) imaging is extensively used for cardiac diseases in small animals due to its high spatial resolution. However, there is a lack of a system that can provide a 2-D high-spatiotemporal dynamic visualization of mouse myocardial strains. In this article, a dynamic HFUS (40 MHz) high-resolution strain imaging was developed through the vector Doppler imaging. Following in vitro tests using a rubber balloon phantom, in vivo experiments were performed on wild-type (WT) and myocardial infarction (MI) mice. High-resolution dynamic images of myocardial strains were obtained in the longitudinal, radial, and circumferential directions at a frame rate of 1 kHz. Global peak strain values for WT mice were -19.3% ± 1.3% (longitudinal), 31.4% ± 1.7% (radial in the long axis), -19.9% ±.8% (circumferential), and 34.4% ± 1.9% (radial in the short axis); those for the MI mice were -16.1% ±.9% (longitudinal), 26.8% ± 2.9% (radial in the long axis), -15.2% ± 2.7% (circumferential), and 21.6% ± 4.8% (radial in the short axis). These results indicate that the strains for MI mice are significantly lower than those for WT mice. Regional longitudinal strain curves in the epicardial, midcardial, and endocardial layers were measured and the peak strain values for WT mice were -22.% and -16.8% in the endocardial and epicardial layers, respectively. However, no significant difference in the layer-based values was noted for the MI mice. Regional analysis results revealed obvious myocardial strain variation in the apical anterior region in the MI mice. The experimental results demonstrate that the proposed dynamic cardiac strain imaging can be useful in high-performance imaging of small-animal cardiac diseases.

Objective: Most neurodegenerative diseases are highly linked with aging. The mechanical properties of the brain should be determined for predicting and diagnosing age-related brain diseases. A preclinical animal study is crucial for neurological disease research. However, estimation of the elasticity properties of different regions of mouse brains remains difficult because of the size of the brain. In this paper, high-frequency ultrasound elastography (HFUSE) based on shear wave imaging was proposed for mapping the stiffness of the mouse brain at different ages ex vivo . Methods: For HFUSE, a 40-MHz ultrasound array transducer with an ultrafast ultrasound imaging system was used in this paper. The accuracy and resolution during HFUSE were determined through a mechanical testing system and by conducting phantom experiments. Results: In the experiments, the error in the elastic modulus measurement was approximately 10% on average, and the axial resolution was 248 μm. Animal testing was conducted using mice that were 4 (young aged) and 11 (middle aged) months old. The elasticity distributions of the cortex and hippocampus in the mouse brains were obtained through HFUSE. Conclusion: The average shear moduli of the cortex and hippocampus were 3.84 and 2.33 kPa for the 4-month-old mice and 3.77 and 1.94 kPa for the 11-month-old mice, respectively. No statistical difference was observed in the cortex stiffness of mice of different ages. However, the hippocampus significantly softened with aging.

Objective: Cerebrovascular disorders are associated with Alzheimer's disease (AD). Functional analysis of the cerebral vasculature requires an in vivo approach to visualize the blood flow in small animal brains. This paper proposes a high-frequency micro-Doppler imaging (HFμDI) technology for mapping mouse cerebral vasculature. Methods: HFμDI used a 40-MHz transducer with an ultrafast ultrasound imaging technology that enabled in vivo visualization of the mouse brain up to 3 mm in depth; furthermore, a minimal vessel diameter of 48 μ m could be determined. Results: Animal experiments determined that the cortical and hippocampal vessel density in young wild-type (WT) mice was similar to that in middle-aged WT mice. However, compared with the vessel density in middle-aged WT mice, that in middle-aged mice with AD was significantly lower, particularly in the hippocampus. Discussion: In vivo observation of cerebral vasculature demonstrated the effectiveness of HFμDI for the preclinical study of AD, and a potential way for human diagnosis was provided.

Motor neuron diseases (MND) including amyotrophic lateral sclerosis and Parkinson disease are commonly neurodegenerative, causing a gradual loss of nerve cells and affecting the mechanisms underlying changes in calcium (Ca

Dementia with Lewy bodies (DLB) is one of the most prevalent forms of neurodegenerative dementia, second to Alzheimer's disease, and autonomic abnormalities and depressive symptoms are common. There are currently no cures or treatments with evidence of disease-modifying effects for DLB, and the treatment for the amelioration of targeted symptoms is challenging due to the risk of side effects and drug-drug interactions. In the present case, we report a female elder with DLB suffering from poor tolerance to the adverse events of numerous approaches. Following intermittent theta burst stimulation (iTBS), the autonomic abnormalities and depressive symptoms remarkably improved without significant side effects.

Purpose Wall shear stress (WSS), a type of friction exerted on the artery wall by flowing blood, is considered a crucial factor in atherosclerotic plaque development. Currently, achieving a reliable WSS mapping of an artery noninvasively by using existing imaging modalities is still challenging. In this study, a WSS mapping based on vector Doppler flow velocity estimation was proposed to measure the dynamic WSS on the human femoral artery. Methods Because ultrafast ultrasound imaging was used here, flow-enhanced imaging was also performed to observe the moving blood flow condition. The performance of WSS mapping was verified using both straight (8 mm in diameter) and stenosis (70% of stenosis) phantoms under a pulsatile flow condition. A human study was conducted from five healthy volunteers. Results Experimental results demonstrated that the WSS estimation was close to the standard value that was obtained from maximum velocity estimation in straight phantom experiments. In a stenosis phantom experiment, a low WSS region was observed at a site downstream of an obstruction, which is a high-risk area for plaque formation. Dynamic WSS mapping was accomplished in measurement in the femoral artery bifurcation. In measurements, the time-averaged WSS of the common femoral artery, superficial femoral artery, and deep femoral artery was 0.52± 0.19, 0.44 ± 0.21, and 0.29 ± 0.16 Pa, respectively, for the anterior wall and 0.29 ± 0.11, 0.54 ± 0.24, and 0.23 ± 0.10 Pa, respectively, for the posterior wall. Conclusions All results indicated that WSS mapping has the potential to be a useful tool for vessel duplex scanning in the future.

Objective: Zebrafish has been recently considered an ideal vertebrate for studying developmental biology, genetics, particularly for modeling tumorigenesis, angiogenesis, and regeneration in vivo . However, when a zebrafish matures completely, its body loses transparency, thus making conventional optical imaging techniques difficult for imaging internal anatomy and vasculature. Acoustic wave penetration outperforms optical methods, high-frequency (>30 MHz) ultrasound (HFUS) was consequently an alternative imaging modality for adult zebrafish imaging, particularly for echocardiography However, visualizing peripheral vessels in a zebrafish by using conventional HFUS is still difficult. Methods: In the present study, high-frequency micro-Doppler imaging (HF μ DI) based on ultrafast ultrasound imaging was proposed for zebrafish dorsal vascular mapping in vivo . HF μ DI uses a 40-MHz ultrasound transducer, which is an ultrafast ultrasound imaging technology with the highest frequency available currently. Blood flow signals were extracted using an eigen-based clutter filter with different settings. Experiments were performed on an 8-month-old wild-type AB-line adult zebrafish. Results: Blood vessels, including intersegmental vessels, parachordal vessel, dorsal longitudinal anastomotic vessel, and dorsal aorta, from the dorsal side of the zebrafish were clearly observed in two-dimensional (2-D) and 3-D HFμDI. Conclusion: The maximum image depth of HFμDI and the minimal diameter of vessel can be detected were 4 mm and 36 μm, respectively; they were determined without any use of microbubbles. The maximum flow velocity range was approximately 3–4 mm/s on the dorsal vessels of the adult zebrafish. Significance: Compared with conventional ultrasound Doppler imaging, HF μ DI exhibited superior small vessel imaging.

In this paper, the pulsewidth modulation switch method was used to investigate the effect of the transformer leakage inductance on the small-signal model in isolated full-bridge converter. A galvanic isolated hard-switching full-bridge converter that operates in constant-current mode is analyzed, confirming that leakage inductance significantly affects the small-signal model, and the influence of leakage inductance can be equivalent to a resistance in series with the converter's output LC filter just as that in phase-shifted full-bridge converter. However, the same leakage inductance in these both converters will lead to different equivalent resistance due to different operating principles. Results of the modified model, simulations, and the experiments are compared to verify the correctness of the model. Moreover, this paper also shows that the Norton equivalent circuit of the charger operates in constant current mode, which can be used to estimate the dynamic behavior of the system.

Ultrasonic technologies show great promise for diagnostic imaging and drug delivery in theranostic applications. The development of functional and molecular ultrasound imaging is based on the technical breakthrough of high frame-rate ultrasound. The evolution of shear wave elastography, high-frequency ultrasound imaging, ultrasound contrast imaging, and super-resolution blood flow imaging are described in this review. Recently, the therapeutic potential of the interaction of ultrasound with microbubble cavitation or droplet vaporization has become recognized. Microbubbles and phase-change droplets not only provide effective contrast media, but also show great therapeutic potential. Interaction with ultrasound induces unique and distinguishable biophysical features in microbubbles and droplets that promote drug loading and delivery. In particular, this approach demonstrates potential for central nervous system applications. Here, we systemically review the technological developments of theranostic ultrasound including novel ultrasound imaging techniques, the synergetic use of ultrasound with microbubbles and droplets, and microbubble/droplet drug-loading strategies for anticancer applications and disease modulation. These advancements have transformed ultrasound from a purely diagnostic utility into a promising theranostic tool.

A simple way to gain 3 to 5x throughput for SRAM E-beam inspection (EBI) through innovative application of Vector Scan Technology is described. EBI, despite many unique advantages, is limited by throughput. Vector Scan technology, developed for patterning weak point inspection, allows hot spots within a very large field of view (FOV) to be scanned, thereby saving both move time plus time wasted on uninteresting pixels. This technology was adapted for VC inspection of SRAM, a common yield driver vehicle, at GLOBALFOUNDRIES for the development of a recent technology, providing an effective throughput gain of 4.2x, for three heavily used inspections.

This paper presents a 32-channel high timing resolution transmit-beamforming circuit for use in high-frequency ultrasound imaging systems. Conventional transmit-beamforming circuits are typically implemented using field-programmable gate array (FPGA) chips. However, it is difficult for FPGAs to provide high timing resolution to meet the beamforming requirements of high-frequency ultrasound imaging systems. The proposed transmit-beamforming design can generate stable and suitable delays to excite 32-channel array transducer elements without variations in the process, voltage, and temperature. In addition, the proposed low-complexity architecture can maintain the duty cycle of long prorogation signals with low hardware cost to meet the timing requirements of a large channel number array transducer. The proposed designed transmit beamformer uses 0.18-µm CMOS technology for a 30-MHz high-frequency linear array, and the simulation results show that the proposed transmit-beamforming application-specific integrated circuit can achieve a maximum time delay of 619.5 ns with a time resolution of 617 ps.

Tongue deformation during whole-night natural sleep in adult patients with obstructive sleep apnea has not been well evaluated. Through simultaneous ultrasonography and polysomnography during whole-night sleep, we examined the prevalence and patterns of tongue depth changes and their relationship with the severity of obstructive sleep apnea. Sixty consecutive eligible adults presenting with symptoms suggesting obstructive sleep apnea were enrolled. We observed that 88.4% (38/43) of patients with obstructive sleep apnea exhibited a significant increase in the maximum ultrasonographic tongue depth when hypopnea or apnea occurred during sleep. A mixed-model analysis of variance demonstrated that compared with patients with primary snoring or mild obstructive sleep apnea, those with moderate to severe obstructive sleep apnea have significantly greater maximum ultrasonographic tongue depth during respiratory events (p = .0047). We identified three different ultrasonographic patterns of tongue deformation, namely en bloc, tongue body and tongue base. Approximately 82% (27/33) of patients with moderate to severe obstructive sleep apnea demonstrated an en bloc tongue deformation. By contrast, 70% (19/27) of primary snorers or patients with mild obstructive sleep apnea showed a tongue body obstruction. Recognizing the prevalence and patterns of tongue deformation during sleep may provide insights into pathogenesis and treatment decisions in patients with obstructive sleep apnea. Future studies are warranted to verify the treatment results of various tongue procedures by using this approach.