In this article, a PZT/Epoxy 1-3 piezoelectric composite based on picosecond laser etching technology is developed for the fabrication of high-frequency ultrasonic transducer. The design, fabrication, theoretical analysis, and performance of the piezocomposite and transducer are presented and discussed. According to the test results, the area of the PZT pillar is 20.5 μm × 20.5 μm, the average width of the kerf is 4.5 μm, and the thickness of the piezocomposite is 38 μm. The fabricated 1-3 piezocomposite has a resonant frequency of 46.5 MHz, a parallel resonant frequency of 65 MHz, and an electromechanical coupling coefficient of 0.73. According to the wires phantom imaging, its imaging resolution can reach 50 μm. This study shows that the proposed picosecond laser micromachining technique can be applied in the fabrication of high frequency 1-3 piezocomposite and transducer.

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.

Due to the small aperture of blood vessel, a considerable disadvantage to current intravascular ultrasound (IVUS) imaging transducers is that their lateral imaging resolution is much lower than their axial resolution. To solve this problem, a single-element, 50 MHz, 0.6 mm diameter IVUS transducer with a geometric focus at 3 mm was proposed in this paper. The focusing transducer was based on a geometric-shaped 1-3 piezocomposite. The impedance/phase, pulse echo, acoustic intensity field, and imaging resolution of the focusing transducer were tested. For comparison, a flat IVUS transducer with the same diameter and 1-3 piezocomposite was made and tested too. Compared with their results, the fabricated focusing transducer exhibits broad bandwidth (107.21%), high sensitivity (404 mV), high axial imaging resolution (80 μm), and lateral imaging resolution (100 μm). The experimental results demonstrated that the high frequency geometric focusing piezocomposite transducer is capable of visualizing high axial and lateral resolution structure and improving the imaging quality of related interventional ultrasound imaging.

Chirp coded excitation is an effective method to improve the signal-to-noise ratio (SNR) and penetration depth of high-frequency endoscopic ultrasound (EUS) imaging. In coded excitation, pulse compression is applied to compress the elongated coded signals into a short pulse, which determines the final imaging performance, including spatial resolution and SNR. However, with the current pulse compression methods, it is hard to get high performance in the peak sidelobe level (PSL), image contrast, and axial resolution at the same time. To solve this problem, in this article, a new method named compressed pulse weighting method (CPWM) was proposed based on the combination of two kinds of pulse compression signals. A brief theoretical derivation proved the feasibility of method. The proposed method was evaluated by the simulation and phantom experiments. Compared with traditional method, the results showed that the proposed adaptive weighting method can provide increases of 32.42% in the penetration depth, 9.48 dB in the SNR, 5.60 dB in the contrast ratio (CR), 5.46 in the contrast-to-noise ratio (CNR), and 0.13 mm in the axial imaging resolution for 12-MHz EUS. Therefore, this method can effectively improve the ultrasound penetration depth and imaging quality, which made it have good potential for high-frequency ultrasound imaging.

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.

High-speed mechanical rotation scanning is the main imaging method of current high-frequency internal ultrasound. Due to uneven drag on the catheter driveshaft leading to changes in the rotational speed, Nonuniform rotational deformity (NURD) is critically limited for the quantitative analysis of internal ultrasound use. To date there have been no techniques shown that provide effective and dynamic modulation of NURD. In this work, a micro structured high-frequency rotary ultrasonic encoder with cylinder gratings was developed, which can dynamically fix the NURD and get high quality restored image. Accordingly, a prototyped micro rotary 50-MHZ ultrasonic encoder with a miniature diameter of 3 mm and a selection of resolutions up to 64 pulses per revolution, which should be the smallest and highest frequency rotary ultrasonic encoder ever reported, was demonstrated based on an endoscopic ultrasound system. The miniature high-frequency rotary ultrasonic encoder shows great potential for ultrasonic endoscopy, OCT, and other mechanical scanning imaging.