A Thickness-Mode High-Frequency Underwater Acoustic Transducer with a Low Sidelobe Level

Thickness vibration mode is commonly used for high-frequency transducers. For disc piezoelectric ceramics, there is no ideally pure thickness vibration mode because the coupling between the radial and thickness modes always exists. Furthermore, it also deteriorates the transmission voltage response and directivity of the high-frequency transducer. In this paper, based on the theoretical calculation and finite element simulation method, a new method was proposed, and the related experiment was carried out to convince this idea. Both the simulation analysis and experimental results show that drilling a hole at the center of piezoelectric vibration is a simple but effective method to obtain a pure thickness vibration mode of the disc piezoelectric ceramic, and then improve the transmitting ability and directivity of the high-frequency piezoelectric transducer. The sidelobe level is as low as −21.3 dB.

Vagus Nerve Cross-Sectional Area in Patients With Parkinson's Disease—An Ultrasound Case-Control Study

Background: Vagal parasympathetic neurons are prone to degeneration in Parkinson's disease (PD). High-resolution ultrasound can precisely estimate the cross-sectional (CSA) area of peripheral nerves. Here, we tested the hypothesis that vagus CSA is reduced in PD.Methods: We included 56 healthy controls (HCs) and 63 patients with PD. Using a high-end ultrasound system equipped with a high-frequency transducer, five images were obtained of each nerve. The hypoechoic neuronal tissue was delineated offline with dedicated software and the CSA extracted.Results: In the initial PD vs. HC comparison, no statistically significant differences were observed in mean left vagus CSA (HC: 1.97 mm2, PD: 1.89 mm2, P = 0.36) nor in mean right vagus CSA (HC: 2.37 mm2, PD: 2.23 mm2, P = 0.17). The right vagus CSA was significantly larger than the left vagus CSA in both groups (P < 0.0001). Females were overrepresented in the HC group and presented with generally smaller vagus CSAs. Consequently, sex-adjusted CSA was significantly smaller for the right vagus nerve of the PD group (P = 0.041), but not for the left.Conclusion: A small but significant reduction in sex-adjusted right vagus CSA was observed in patients with PD. The left vagus CSA was not significantly reduced in patients with PD. Ultrasound may not be a suitable method to detecting vagal axonal loss in individual patients.

Imaging Capability at Close Range of High Frequency Ultrasound Transducer on the Perforation of Bony Walls Simulating Pedicle Screw Placement

Background: Ultrasound has been proved to be a promising alternative spine navigation method. High frequency ultrasound transducer has the advantage of high resolution on surface structure, but imaging at close range is difficult, especially in narrow space of the pilot-hole in pedicle.Methods: Twenty cortical bone chips were made and different size of hole with diameter of 1mm, 2mm, 3mm or 5mm was randomly carved in each bone chip. A tailored 30MHz high frequency transducer scanned bone samples at the distance of 4mm, 3mm, 2mm and 1mm. Successive transmission ringingeffect elimination, Hilbert transform and Gray-scale mapping method were utilized to process and optimize attained original images.Results: At the distance of 4mm, 3mm, 2mm and 1mm, the holes with diameter of 5mm, 3mm and 2mm could be discerned. At the distance of 1mm, only the holes with 5mm and 3mm could be clearly distinguished and the 2mm hole appeared obscure. The holes with diameter of 1mm could not be detected at any distance. The holes with diameter of 2mm were able to be detected at the distance of 1mm.Conclusions: This study indicated that the high frequency transducer had limited imaging capability at close range on the bony surface. These results lay a foundation for further developing a novel ultrasound-based spinal pedicle interior imaging and navigation system.

Vagus nerve cross-sectional area in patients with Parkinson’s Disease – an ultrasound case-control study

BackgroundVagal parasympathetic neurons are prone to degeneration in Parkinson’s disease (PD). High-resolution ultrasound can precisely estimate the cross-sectional area (CSA) of peripheral nerves. Here, we tested the hypothesis that vagus CSA is reduced in PD.MethodsWe included 56 healthy controls (HCs) and 63 patients with PD. Using a high-end ultrasound system equipped with a high-frequency transducer, five images were obtained of each nerve. The hypoechoic neuronal tissue was delineated offline with dedicated software and the CSA extracted.ResultsIn the initial PD vs. HC comparison, no statistically significant differences were observed in mean left vagus CSA (HC: 1.97mm2, PD: 1.89mm2, P=0.36) or in mean right vagus CSA (HC: 2.37mm2, PD: 2.23mm2, P=0.17). The right vagus CSA was significantly larger than the left vagus CSA in both groups (P<0.0001). Females were overrepresented in the HC group and presented with generally smaller vagus CSAs. Consequently, sex-adjusted CSA was significantly smaller for the right vagus nerve of the PD group (P=0.041), but not for the left.ConclusionA small but significant reduction in sex-adjusted right vagus CSA was observed in patients with PD. The left vagus CSA was not significantly reduced in patients with PD. Ultrasound may not be a suitable method to detecting vagal axonal loss in individual patients.

WFUMB position paper on reverberation artefacts in lung ultrasound: B-lines or comet-tails?

The analysis of vertical reverberation artefacts is an essential component of the differential diagnosis in pulmonary ultra-sound. Traditionally, they are often, but not exclusively, called B-line artefacts (BLA) and/or comet tail artefacts (CTA), but this view is misleading. In this position paper we clarify the terminology and relation of the two lung reverberation artefacts BLA and CTA to spe-cific clinical scenarios. BLA are defined by a normal pleura line and are a typical hallmark of cardiogenic pulmonary edema after exclusion of certain pathologies including pneumonia or lung contusion, whereas CTAs show an irregular pleura line representing a variety of parenchymal lung diseases. The dual approach using low frequency transducers to determine BLA and high frequency transducer to determine the pleural surface is recommended.

Design of a Multichannel Pulser/Receiver and Optimized Damping Resistor for High-Frequency Transducer Applied to SAM System

Scanning acoustic microcopy (SAM) is widely used in biomedical and industrial applications in dermatology, ophthalmology, intravascular imaging, and small animal images, owing to SAM’s ability to photograph small structures with a good spatial resolution. One of the most important devices of this system is the pulser/receiver (P/R) (PRN-300, Ohlabs Corporation, Nam-gu Busan, Republic of Korea), which generates pulses to trigger a high-frequency transducer. This article presents the design of a pulse generator to excite high-frequency transducers with four channels. The characteristics of the pulses, such as time and frequency, can be reconfigured by using a high-speed field programmable gate array (FPGA). The configuration software was developed for communicating with the P/R device via a USB connector for easy, feasible pulse selection and real-time pulse management. Besides that, during the design and implementation of the hardware, we optimized the damping resistor value to reduce the overshoot and undershoot part of the signal, ensuring the best effect on the transducer signal. The test results show that unipolar pulses worked with transducers with frequencies over 100 MHz. The SAM systems can work simultaneously with multiple transducers, and the resulting images have different resolutions of regions.

Identification of Ulnar Artery Perforators Using Color Doppler Ultrasonography

Background The ulnar artery perforator (UAP) flap, which is hairless, thin, and pliable, has been used for the reconstruction of soft tissues from the finger to the elbow. Preoperative planning is essential for a perforator flap surgery, and there are some tests to identify perforators. Color Doppler ultrasonography (US) with a high-frequency transducer helps in detecting decreased flow in smaller vessels, such as perforators. The purpose of this study was to determine the anatomical locations and origins of perforators arising from the ulnar artery using color Doppler US in healthy volunteers. Methods Forty forearms of 20 healthy volunteers were included in the study. Perforators arising from the ulnar artery, within 100 mm proximal to the pisiform, were investigated using color Doppler US with a high-frequency transducer. Results A total of 205 perforators were identified. On comparing the locations in each 20 mm section from the pisiform, the largest number of perforators was 58 (28%), within 20 mm proximal to the pisiform. The axial view demonstrated 44 (21%), 64 (31%), 32 (16%), and 65 (32%) perforators in the radial, ulnar, superficial, and deep aspects of the ulnar artery, respectively. Fifty-two and 28 essential perforators were supplied by the UAPs arising from the superficial and ulnar aspect within 20 mm proximal to the pisiform and between 21 and 40 mm proximal to the pisiform, respectively, while elevating the UAP flap. Conclusion This is the first study to assess the UAP using color Doppler US. Identification of UAP using color Doppler US can be used as a preoperative assessment for reliable elevation of a UAP flap.