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Eye blinking is closely related to human physiology and psychology. It is an effective method of communication among people and can be used in human–machine interactions. Existing blink monitoring methods include video-oculography, electro-oculograms and infrared oculography. However, these methods suffer from uncomfortable use, safety risks, limited reliability in strong light or dark environments, and infringed informational security. In this paper, we propose an ultrasound-based portable approach for eye-blinking activity monitoring. Low-power pulse-echo ultrasound featuring biosafety is transmitted and received by microelectromechanical system (MEMS) ultrasonic transducers seamlessly integrated on glasses. The size, weight and power consumption of the transducers are 2.5 mm by 2.5 mm, 23.3 mg and 71 μW, respectively, which provides better portability than conventional methods using wearable devices. Eye-blinking activities were characterized by open and closed eye states and validated by experiments on different volunteers. Finally, real-time eye-blinking monitoring was successfully demonstrated with a response time less than 1 ms. The proposed solution paves the way for ultrasound-based wearable eye-blinking monitoring and offers miniaturization, light weight, low power consumption, high informational security and biosafety. [ABSTRACT FROM AUTHOR]

Approximately 80% of men who reach 80 years of age will have some form of prostate cancer. The challenge remains to differentiate benign and malignant lesions. Based on recent research, acoustic angiography, a novel contrast-enhanced ultrasound imaging technique, can provide high-resolution visualization of tissue microvasculature and has demonstrated the ability to differentiate vascular characteristics between healthy and tumor tissue in preclinical studies. We hypothesize that transrectal acoustic angiography may enhance the assessment of prostate cancer. In this paper, we describe the development of a dual frequency, dual-layer colinear array transducer for transrectal acoustic angiography. The probe consists of 64 transmitting (TX) elements with a center frequency of 3 MHz and 128 receiving (RX) elements with a center frequency of 15 MHz. The dimensions of the array are 18 mm in azimuth and 9 mm in elevation. The pitch is $280~\mu \text{m}$ for TX elements and 140 $\mu \text{m}$ for RX elements. Pulse-echo tests of TX/RX elements and aperture acoustic field measurements were conducted, and both results were compared with the simulation results. Real-time contrast imaging was performed using a Verasonics system and a tissue-mimicking phantom. Nonlinear acoustic responses from microbubble contrast agents at a depth of 35 mm were clearly observed. In vivo imaging in a rodent model demonstrated the ability to detect individual vessels underneath the skin. These results indicate the potential use of the array described herein for acoustic angiography imaging of prostate tumor and identification of regions of neovascularization for the guidance of prostate biopsies. [ABSTRACT FROM AUTHOR]

Recent studies suggest that dual-frequency intravascular ultrasound (IVUS) transducers allow detection of superharmonic bubble signatures, enabling acoustic angiography for microvascular and molecular imaging. In this paper, a dual-frequency IVUS cylindrical array transducer was developed for real-time superharmonic imaging. A reduced form-factor lateral mode transmitter (2.25 MHz) was used to excite microbubbles effectively at 782 kPa with single-cycle excitation while still maintaining the small size and low profile (5 Fr) (3 Fr = 1 mm) for intravascular imaging applications. Superharmonic microbubble responses generated in simulated microvessels were captured by the high frequency receiver (30 MHz). The axial and lateral full-width half-maximum of microbubbles in a 200-μm-diameter cellulose tube were measured to be 162 μm and 1039 μm, respectively, with a contrast-to-noise ratio (CNR) of 16.6 dB. Compared to our previously reported single-element IVUS transducers, this IVUS array design achieves a higher CNR (16.6 dB vs 11 dB) and improved axial resolution (162 μm vs 616 μm). The results show that this dual-frequency IVUS array transducer with a lateral-mode transmitter can fulfill the native design requirement (∼3–5 Fr) for acoustic angiography by generating nonlinear microbubble responses as well as detecting their superharmonic responses in a 5 Fr form factor. [ABSTRACT FROM AUTHOR]

Techniques to image the microvasculature may play an important role in imaging tumor-related angiogenesis and vasa vasorum associated with vulnerable atherosclerotic plaques. However, the microvasculature associated with these pathologies is difficult to detect using traditional B-mode ultrasound or even harmonic imaging due to small vessel size and poor differentiation from surrounding tissue. Acoustic angiography, a microvascular imaging technique that utilizes superharmonic imaging (detection of higher order harmonics of microbubble response), can yield a much higher contrast-to-tissue ratio than second harmonic imaging methods. In this paper, two dual-frequency transducers using lateral mode transmitters were developed for superharmonic detection and acoustic angiography imaging in intracavity applications. A single element dual-frequency intravascular ultrasound transducer was developed for concept validation, which achieved larger signal amplitude, better contrast-to-noise ratio (CNR), and pulselength compared to the previous work. A dual-frequency [Pb(Mg1/3Nb2/3)O3]–x[PbTiO3] array transducer was then developed for superharmonic imaging with dynamic focusing. The axial and lateral sizes of the microbubbles in a 200- \mu \textm tube were measured to be 269 and 200~\mu \textm , respectively. The maximum CNR was calculated to be 22 dB. These results show that superharmonic imaging with a low frequency lateral mode transmitter is a feasible alternative to thickness mode transmitters when the final transducer size requirements dictate design choices. [ABSTRACT FROM AUTHOR]

Ultrasound imaging with high resolution and large penetration depth has been increasingly adopted in medical diagnosis, surgery guidance, and treatment assessment. Conventional ultrasound works at a particular frequency, with a - 6\text-dB fractional bandwidth of \sim\text70\% , limiting the imaging resolution or depth of field. In this paper, a bifrequency colinear array with resonant frequencies of 8 and 20 MHz was investigated to meet the requirements of resolution and penetration depth for a broad range of ultrasound imaging applications. Specifically, a 32-element bifrequency colinear array was designed and fabricated, followed by element characterization and real-time sectorial scan (S-scan) phantom imaging using a Verasonics system. The bifrequency colinear array was tested in four different modes by switching between low and high frequencies on transmit and receive. The four modes included the following: 1) transmit low, receive low; 2) transmit low, receive high; 3) transmit high, receive low; and 4) transmit high, receive high. After testing, the axial and lateral resolutions of all modes were calculated and compared. The results of this study suggest that bifrequency colinear arrays are potential aids for wideband fundamental imaging and harmonic/subharmonic imaging. [ABSTRACT FROM PUBLISHER]

Capacitive micromachined ultrasonic transducer (CMUT) has shown the potential for the air-coupled application due to its good acoustic match with air. Therefore, air-coupled guided wave detection technology based on CMUT array has a good application prospect in structure detection. In this paper, a 16-element CMUT array for air-coupled guided wave detection is designed and fabricated by the silicon-on-insulator (SOI) wafer bonding process. All the CMUT cells have the same geometric parameters with circular and sealed membrane. Each element has good consistency in impedance and transceiver performance. In addition, the transmit performance was improved by a third through impedance matching. The resonant frequency is 207 kHz at 150 DC voltage and − 6 dB main lobe width of the sound beam is 9.4°. The emission beam can be steered by programmable driving circuit. So different modes of guided wave can be excited without adjusting the tilt angle of the transducer. This will reduce the interference caused by the movement of device in the experiment. After that, the air-coupled guided wave detection experiment was carried out by two CMUT arrays. The results show that the CMUT array can well excite the single mode Lamb wave in aluminum plate and composite plate, and receive the leaky Lamb wave. Besides, the defect can be identified by the variation of the received signal amplitude. Thus, the position of the defect can be located and the approximate size of the defect can be predicted. In general, it is proved that the CMUT has ability for the air-coupled Lamb wave detection by the non-contact guided wave detection experiment and the comparison experiment with commercial air coupling probe. [Display omitted] • A 16-element CMUT array for air-coupled guided wave detection is designed and fabricated by SOI wafer bonding process. • Each element has good consistency by acoustic and electrical properties test and the performance is improved by impedance matching. • The CMUT can excite the single mode Lamb wave in plate and receive the leaky Lamb wave,。Besides, the defect can be identified. [ABSTRACT FROM AUTHOR]