Ultrathin endoscope equipped with ultrasonic miniprobe for upper GI US in a porcine model.

BACKGROUND AND AIMS: Ultrathin EGD (UT-EGD) is an ideal tool for unsedated upper GI examination and pediatric gastroenterology but is rarely competent for EUS miniprobe (EUS-MP). We developed a UT-EGD US method (UT-EUS) and verified its clinical application value through animal experiments. METHODS: Five Bama miniature pigs were selected. Using an acoustic medium, we performed US on the duodenum, stomach, and esophagus, respectively, with conventional 20-MHz EUS miniprobe (EUS-MP-20), 20-MHz UT-EUS (UT-EUS-20), and 30-MHz UT-EUS (UT-EUS-30). The times to acquire 5 consecutive stable US images, number of identifiable wall layers, and quality and penetration depth of the images were recorded. RESULTS: No significant differences were found in the time required to obtain images between EUS-MP-20 and UT-EUS-20 at each site (P > .05). UT-EUS-30 showed more wall levels than UT-EUS-20 (P < .05). No significant differences were noted between EUS-MP-20 and UT-EUS-20 in imaging quality and penetration depth (P > .05). CONCLUSIONS: The UT-EUS is easy to use with a satisfactory image quality and has potential clinical application value.

High-Frequency Endoscopic Ultrasound Imaging With Phase-Corrected-and-Sum and Coherence Factor Weighting.

High-frequency endoscopic ultrasound (HFEUS) imaging is an important tool commonly used in clinical practice for imaging hollow organs. The virtual source synthetic aperture (VSSA) method is effective in improving the imaging quality of HFEUS. However, interference from the motor control unit severely affects the accuracy of the conventional delay and sum (DAS) method, thus compromising the effectiveness of VSSA. In this article, a new computational method based on phase correction was proposed to overcome these shortcomings, which is named phase-corrected-and-sum (PCAS). Meanwhile, the parameters of coherence factor weighting (CFW) can be obtained from the correlation coefficient of the superimposed signals to further increase the imaging quality. Three kinds of imaging experiments were designed to evaluate the proposed method. Compared with the conventional method, the results show that the PCAS-CFW method improves the lateral resolution by about 10% and the contrast-to-noise ratio (CNR) by about 44%. Therefore, this proposed method is capable of significantly improving HFEUS image quality, and this method can be easily integrated into current HFEUS imaging systems, showing great potential for clinical applications.

Micromachined High Frequency 1-3 Piezocomposite Transducer Using Picosecond Laser.

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 [Formula: see text], the average width of the kerf is [Formula: see text], and the thickness of the piezocomposite is [Formula: see text]. 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 [Formula: see text]. This study shows that the proposed picosecond laser micromachining technique can be applied in the fabrication of high frequency 1-3 piezocomposite and transducer.

Sensitivity Enhanced Photoacoustic Imaging Using a High-Frequency PZT Transducer with an Integrated Front-End Amplifier.

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.

A High Frequency Geometric Focusing Transducer Based on 1-3 Piezocomposite for Intravascular Ultrasound Imaging.

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.

A Modified 2D Multiresolution Hybrid Algorithm for Ultrasound Strain Imaging.

Ultrasound elastography is an imaging modality to evaluate elastic properties of soft tissue. Recently, 1D quasi-static elastography method has been commercialized by some companies. However, its performance is still limited on high strain level. In order to improve the precision of estimation during high compression, some algorithms have been proposed to expand the 1D window to a 2D window for avoiding the side-slipping. But they are usually more computationally expensive. In this paper, we proposed a modified 2D multiresolution hybrid method for displacement estimation, which can offer an efficient strain imaging with stable and accurate results. A FEM phantom with a stiffer circular inclusion is simulated for testing the algorithm. The elastographic contrast-to-noise rate (CNRe) is calculated for quantitatively comparing the performance of the proposed algorithm with conventional 1D elastography using phase zero estimation and the 1D elastography using downsampled (d-s) baseband signals. Results show that the proposed method is robust and performs similarly as other algorithms in low strain but is superior when high level strain is applied. Particularly, the CNRe of our algorithm is 15 times higher than original method under 4% strain level. Furthermore, the execution time of our algorithm is five times faster than other algorithms.

Design of micromachined self-focusing piezoelectric composite ultrasound transducer.

Based on the Fresnel half-wave band interference, a micromachined self-focusing piezoelectric composite ultrasound transducer was proposed in this paper. The theoretical analysis was deduced based on the concept of constructive interference of acoustic waves and electromechanical response of piezoelectric composites. The calculated and simulation results showed that it combined the advantages of composite transducer and plate self-focusing transducer, and can achieve high electromechanical coupling coefficient, low acoustic impedance, high intensity, short focal length and micro size. Because it was based on the micro-electromechanical systems, the fabrication process was accurate and controllable, which made it have good potential for interventional ultrasound imaging, cellular microstructure imaging, skin cancer detection and industrial nondestructive testing applications.