In this study, we present a united sign coherence factor beamformer for coherent plane-wave compounding (CPWC). CPWC is capable of reaching an image quality comparable to the conventional B-mode with a much higher frame rate. Conventional coherence factor (CF) based beamformers for CPWC are based on one-dimensional (1D) frameworks, either in the spatial coherence dimension or angular coherence dimension. Both 1D frameworks do not take into account the coherence information of the dimensions of each other. In order to take full advantage of the radio-frequency (RF) data, this paper proposes a united framework containing both spatial and angular information for CPWC. A united sign coherence factor beamformer (uSCF), which combines the conventional sign coherence factor (SCF) and the united framework, is introduced in the paper as well. The proposed beamformer is compared with the conventional 1D SCF beamformers (spatial and angular dimension beamformers) using simulation, phantom and in vivo studies. In the in vivo images, the proposed method improves the contrast ratio (CR) and generalized contrast-to-noise ratio (gCNR) by 197% and 20% over CPWC. Compared with other 1D methods, uSCF also shows an improved contrast and lateral resolution on all datasets.

Atherosclerosis accounts for over 30% of global deaths annually. The intravascular ultrasound (IVUS) can provide detailed information on lesions, enabling accurate diagnosis, and treatment of vascular diseases. The existing IVUS catheters face challenges to work in tortuous blood vessels. This study presents a dual-mode magnetic IVUS robot, featuring by miniature size and high softness, which allows for intravascular imaging in hard-to-reach regions. First, the magnetic IVUS robot consisting of an acoustic-magnetic tip and a soft catheter is designed, which performs: 1) controllable bending under static magnetic fields to navigate in complex vasculature; 2) shaft-free acoustic beam scanning under dynamic magnetic fields to provide high-resolution ultrasound images. Then, the motion modeling of navigating mode and imaging mode are analyzed, respectively. Next, an integrated system and actuating strategy are established, realizing the dual-mode decoupling control of the magnetic IVUS robot. Finally, the effectiveness of the presented method is validated in vascular models, imaging phantoms, and in-vitro porcine artery vessel. The designed magnetic IVUS robot achieves dual objectives, including active angle steering at bifurcations and acoustic beam scanning at lesions, simultaneously improving the operating flexibility and imaging stability. The proposed design and control scheme demonstrate the feasibility of tortuous intravascular imaging, providing a potential solution for clinical applications.

Endoscopic ultrasound (EUS) has the ability to image tissue in and beyond the wall of the gastrointestinal (GI) tract, assisting in the early diagnosis of digestive diseases. However, traditional EUS based on flexible endoscopes could make the operation procedure traumatic and intolerable to patients; moreover, certain areas such as most of the small intestine are generally hard to image due to the limited accessibility. To perform endoluminal US imaging in hard-to-reach GI tract, this study proposes a novel magnetically-actuated ultrasound capsule endoscope (MUSCE). Firstly, the MUSCE consisting of a rotatory magnetic-acoustic head and a stable soft tether is designed, featuring small dimensions, low cost, and active locomotion. Next, the magnetic force-modulated torque actuation principle and the corresponding control strategy and US image reconstruction algorithm are analyzed, enabling simultaneous active motion and B-scan ultrasonic imaging. Finally, the effectiveness of the MUSCE is validated by locomotion and imaging tests. Results demonstrate that the designed MUSCE could perform active motion (maximum speed of $\sim$ 13.8 mm/s) and B-scan US imaging (resolution of $\sim$84.2 $\mu$m) in tubular environments with mitigated discomfort, providing a potential solution for clinical applications.

An ultrasonic needle-actuating device for tissue biopsy and regional anaesthesia offers enhanced needle visibility with color Doppler imaging. However, its specific performance is not yet fully determined. This work investigated the influence on needle visibility of the insertion angle and drive voltage, as well as determined the accuracy and agreement of needle tip localization by comparing color Doppler measurements with paired photographic and B-mode ultrasound measurements. Needle tip accuracy measurements in a gelatin phantom gave a regression trend, where the slope of trend is 0.8808; coefficient of determination (R²) is 0.8877; bias is −0.50 mm; and the 95% limits of agreement are from −1.31 to 0.31 mm when comparing color Doppler with photographic measurements. When comparing the color Doppler with B-mode ultrasound measurements, the slope of the regression trend is 1.0179; R² is 0.9651; bias is −0.16 mm; and the 95% limits of agreement are from −1.935 to 1.605 mm. The results demonstrate the accuracy of this technique and its potential for application to biopsy and ultrasound guided regional anaesthesia.

Photoacoustic (PA) imaging is a hybrid imaging technique that can provide both structural and functional information of biological tissues. Due to limited permissible laser energy deposited on tissues, highly sensitive PA imaging is required. Here, we developed a 20 MHz lead zirconium titanate (PZT) transducer (1.5 mm × 3 mm) with front-end amplifier circuits for local signal processing to achieve sensitivity enhanced PA imaging. The electrical and acoustic performance was characterized. Experiments on phantoms and chicken breast tissue were conducted to validate the imaging performance. The fabricated prototype shows a bandwidth of 63% and achieves a noise equivalent pressure (NEP) of 0.24 mPa/√Hz and a receiving sensitivity of 62.1 μV/Pa at 20 MHz without degradation of the bandwidth. PA imaging of wire phantoms demonstrates that the prototype is capable of improving the detection sensitivity by 10 dB compared with the traditional transducer without integrated amplifier. In addition, in vitro experiments on chicken breast tissue show that structures could be imaged with enhanced contrast using the prototype and the imaging depth range was improved by 1 mm. These results demonstrate that the transducer with an integrated front-end amplifier enables highly sensitive PA imaging with improved penetration depth. The proposed method holds the potential for visualization of deep tissue structures and enhanced detection of weak physiological changes.

Tele-ultrasound imaging is useful in various situations. Plane wave imaging provides a method for ultrafast ultrasound with very high frame rates, which sacrifices image quality and leads to the problem of a large amount of data and low signal transmission speed in telemedicine imaging. In this paper, a novel compressive frequency-wavenumber domain beamforming method is introduced, which integrates Stolt’s f-k method and compressed sensing theory on the lateral wavenumber. The data load is reduced by the sparsity of the echo signal parallel to the transducer, which requires a smaller measurement matrix during compressed sensing to reduce memory usage and accelerate the transmission rate. The signal is compressed in the Fourier domain to obtain greater stability and better image quality after reconstruction than if it was compressed in the temporal domain. Simulated data and experimental acquisitions were used to compare compressive Fourier domain beamforming with conventional delay-and-sum (DAS) beamforming. The results showed that compressive beamforming within the wavenumber domain provides the image with higher quality from less data.