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Aluminum nitride (AlN) Lamb wave resonators (LWRs) utilizing the lowest symmetric (S0) mode have attracted much interests since they have high frequencies, low motional impedances, and capability of multiple frequencies on a single chip. However, the transverse spurious modes are often strong in AlN LWR, and largely degrade the performance in application, so suppression the transverse mode is highly...
Diverging wave imaging is the most prominent transmit sequence in fast cardiac imaging. Indeed, as this type of ultrasound transmit insonifies a significant part of the region of interest at once, less transmit events are required to reconstruct an entire image leading to an improved time resolution. However, the flipside of this approach is that image quality reduces in terms of spatial resolution,...
Fast cardiac imaging using diverging waves (DW) is receiving much attention. Coherent compounding is important to keep spatial resolution and CNR acceptable. Two approaches have been presented in literature to do so: i) the full aperture of the probe is used and the virtual focus is moved along an arc centered at the center of the probe (ARC); ii) a sub-aperture is used and the virtual focus is linearly...
A row-column-addressed (RCA) 2-D array can be interpreted as two orthogonal 1-D arrays. Since the transmit and receive 1-D arrays are orthogonal to each other, only one-way focusing is possible in each transmit or receive plane. By transmitting with row elements and receiving the echoes through column elements, a rectilinear volume in front of the array can be beamformed. This study suggests to use...
Based on the linear relationship of channel data between synthetic transmit aperture (STA) and apodized plane wave (PW) firings, we previously proposed compressed sensing (CS) based STA (CS-STA) for linear array, which achieves higher frame rate and higher contrast-to-noise ratio (CNR) than STA while maintaining its high resolution. Because diverging wave (DW) instead of PW is usually adopted in phased...
The Delay-Multiply-And-Sum (DMAS) beamformer has recently been presented in the context of medical ultrasound image formation. Images obtained with the DMAS beamformer present improved contrast resolution and noise rejection when compared to images obtained with the standard Delay-And-Sum (DAS) beamformer. We study here the signal statistics for a homogeneous medium using both the DAS and DMAS beamformers...
Histotripsy uses high-pressure, microsecond-length pulses to generate cavitation microbubbles to fractionate targeted tissue. After the collapse of a cavitation cloud, remnant microbubbles can persist for a second or longer before passively dissolving. These bubbles can act as seed nuclei for subsequent cavitation events reducing treatment efficiency because the nuclei are not well distributed through...
Pulmonary embolism (PE) is the third-leading cause of death from cardiovascular disease. Currently, PE is treated via catheter-delivered, ultrasound-enhanced thrombolysis using side-fired, low-intensity ultrasound energy (0.5 W/cm2) at ∼2 MHz to reduce the required dose of thrombolytic drugs because of the enhanced drug penetration into the clot. However, several clinical studies have shown that the...
We have developed a new, fast and simple 3D imaging approach referred to as Simultaneous Azimuth and Fresnel Elevation (SAFE) compounding. The principle behind this technique is to perform conventional plane wave compounding with the bottom set of electrodes, while implementing a reconfigurable Fresnel elevation lens with the top electrodes. While a Fresnel lens would usually result in unacceptable...
Transcranial Doppler Ultrasound (TCD) is one of the techniques that have been used for stroke diagnosis. This paper compares the potential of three aperiodic sparse array configurations: random array; sunflower spiral array; and log spiral array for application to TCD. To cover the full temporal window, a 30mm diameter circular aperture is selected, with a 2MHz operating frequency to match current...
Vector Doppler techniques are ready to substitute the standard Doppler methods currently employed in clinical blood velocity investigations. However, like in classic Pulse-Wave modes, the maximum detectable velocity is related to the Pulse Repetition Frequency (PRF), which is limited by the maximum depth and/or by hardware constraints. Unfortunately, the blood velocity, e.g. in stenotic vessels, can...
Lateral resolution and therefore image quality in ultrasound is tied to aperture size. While this relationship is understood in ideal imaging conditions, the utility of a large aperture in the presence of clutter is unknown. This problem is particularly relevant to abdominal imaging where thick tissue layers and deep targets create a challenging imaging environment. Previous studies have focused on...
Focused ultrasound can effectively treat tumors by thermal ablation, but treatment times associated with mechanical or electronic scanning of single foci can be prohibitively long. Maximizing the energy efficiency of focused ultrasound ablation may decrease treatment time while also decreasing sensitivity to perfusion. One proposed approach [Mast et al., US Patent 9132287, 2015] creates multiple foci...
Over the course of accelerated failure testing of 2-port SAW delay line resonators on quartz, periodic acoustomigration damage patterns with acoustic apertures of less than 6 wavelengths were observed across the fully metalized region between the transducers, while typical electrode stress damage was observed over the acoustic aperture in the transducer gratings. This suggested the power density had...
Synthetic aperture (SA) ultrasound imaging is a well-known technique in which RF signals for every transmit and receive element combinations is first obtained and a 2-way-focused image is synthetically formed afterwards. Despite its benefits, one of its main shortcomings is reduced penetration depth caused by low acoustic power from single element firing. To address this challenge, we propose a spatial...
Image quality of volumetric intracardiac echocardiography (ICE) catheters is severely limited, especially in the elevation direction, restricted by the catheter diameter. A natural idea is to design a foldable transducer with multiple panes which can be expanded in the heart mechanically to form a large and symmetric 2-D aperture 2–3 times the size of the catheter diameter. Here, the imaging performance...
Stillbirth is when a baby is born without signs of life after 24 weeks of gestation. Stillbirth prevention depends on healthcare access and in-time diagnosis. Moreover, antenatal tests are not always effective for stillbirth prediction and evaluation. Pregnancy home monitoring can possibly aid stillbirth diagnosis. The aim of this study is to investigate Doppler solutions for pregnancy home monitoring...
Ultrafast imaging based on coherent plane-wave compounding improves image quality and allows for much faster acquisition. This method, however, is limited by severe computational loads stemming from delay-and-sum beamforming (DAS BF) that creates a major bottleneck for real-time implementation. Spatial-temporal (ST) processing yields the entire frame without a need for DAS BF of each image line. First,...
Off-axis clutter is a significant cause of image degradation in ultrasound. We propose an adaptive approach for clutter reduction based on the principle that off-axis signals show as relatively high spatial frequencies in the per-channel data. For each pixel, an M∗N per-channel data matrix is extracte from the aligned data received from different observations of that pixel (N = number of channels,...
RF Voltage transformers operating in one of the ISM frequency bands have recently been demanded in emerging low-power applications, such as wake-up radios in wireless networks, remotely triggered switches, stand-by units in home electronics, etc. S0 Lamb wave resonant (LWR) transformers have been first proposed. Later, SAW transformers designed as “degenerated” CRF have been proposed. Here we demonstrate...
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