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Flow velocity estimation is an important feature in ultrasound imaging. However, in conventional color Doppler imaging, only parallel flow components can be estimated, the velocity information is not simultaneously measured throughout the region of interest (ROI) due to sequential firing of the ultrasound beams, and the size of the ROI is limited under frame rate concerns. On the other hand, ultrafast...
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...
We present an ultrasonic transit-time gas flow meter (UFM) that features a 40-kHz 8×8 2D-phased array for transmitting ultrasonic sound waves up- and downstream to two single element receivers. This allows us to electronically compensate for the well-known parasitic sound drift effect, resulting in larger measurement range and better signal-to-noise-ratio (SNR). The UFM fabricated consists of a pipe...
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...
High-intensity focused ultrasound (HIFU) have been an attractive research topic for some time now. HIFU studies have started with single-element transducers, but using arrays provide the opportunity to scan the focal point electronically. Modular and scalable driving systems that can be used with custom-made transducer elements to drive these arrays are needed and at the present time there are few...
In conventional ultrasonic monitoring of high intensity focused ultrasound (HIFU) treatment, it has been difficult to track the target region when the tissue to be treated deviates from the imaging plane along the elevation axis of the 1-D probe. A 2-D phased array probe providing 3-D imaging capability requires a large number of elements and it is very expensive to build a system to drive all channels...
In this paper, we present a front-end integrated circuit (IC) for an ultrasound neurostimulation system, to be interfaced with a 16×16 2D CMUT array to realize an ultrasound field pattern (USFP) using quantized phases and amplitudes. The IC uses a pulse width modulation (PWM) technique with a three-level pulse to generate excitation signals having multi-level quantized amplitudes. For a programmable...
We present an ultrasonic transit-time gas flow meter (UFM) that features a 40-kHz 2D-phased array for transmitting ultrasonic sound waves up- and downstream to two single element receivers. This allows us to electronically compensate for the well-known parasitic sound drift effect, and, thus, increasing the measurement range by improving the signal-to-noise-ratio (SNR). A regular double-path UFM consists...
Laser Induced Phased Arrays (LIPAs) use post processing to focus and steer the laser generated and detected ultrasonic beam, synthesizing a phased array. The technique is broadband, non-contact, and couplant free, making LIPAs suitable for large stand-off distances, inspection of components of complex geometries and hazardous environments. This paper presents LIPAs synthesized by capturing the Full...
ARFI displacements have been shown to share an inverse relationship with shear wave speed — based estimates of tissue elasticity. Both ARFI and shear wave elasticity imaging (SWEI) have been used to track the stiffening and softening of myocardium through the cardiac cycle in open-chest, intracardiac, and Langendorff preparations. In transthoracic imaging, induced shear waves have been observed during...
Imaging using the total focusing method (TFM) is a popular tool in nondestructive evaluation and it becomes a standard. From full matrix capture, this method consists in focusing at each point of a defined reconstruction zone. It is generally more efficient than conventional phased array focusing that can focus at only a few points. Despite the good quality of TFM images, TFM suffers from a lack of...
Neuromodulation with low intensity focused ultrasound has many potential applications. One target of interest is the nucleus accumbens which is the reward center of the brain. It is hypothesized that with proper stimulation of the nucleus accumbens addictive behavior can be suppressed. Carrying out animal studies to understand the effects of LIFU parameters on such behavioral changes is an important...
The arrival time detection probability and the measurement range of transit-time ultrasonic flow meters are undermined by the sound drift effect. One solution to this problem is utilizing a phased-array beam steering technique to compensate the bend of the ultrasonic beams. The design, the fabrication and the characterization of two-dimensional flexural ultrasonic phased arrays is investigated in...
The non-invasive cortical bone quality assessments using ultrasound axial transmission technique have attracted strong attention. The estimation of phase velocity and attenuation of absorbing plate should help the assessment. To get the high-resolution estimation, we employ an adaptive beamforming technique that uses an eigenvalue decomposition. The technique can estimate not only the phase velocities...
Transit-time ultrasonic flow meters, measuring the time difference between upstream and downstream propagation of ultrasonic beams, have been widely utilized to obtain the average velocity of flow in many applications including natural gas flow rate measurement. The signal-to-noise ratio (SNR) of the ultrasonic signals frequently suffers from the sound drift effect, and thus, the arrival time detection...
Coded excitation with complementary Golay codes has been demonstrated to increase the signal-to-noise ratio (SNR) and penetration of diverging wave (DW) coherent compounding for high frame rate cardiac imaging (Zhao et al., PMB 2017). However, the effective gain in frame rate of the Golay coded system is compromised by a factor of 2 because two complementary codes are transmitted. The objectives of...
Automated robotic inspection systems allow the collection of large data volumes, compared to existing inspection systems. To maximize the throughput associated with the nondestructive evaluation phase, it is crucial that the reconstructed inspection data sets are generated and examined rapidly without a loss of detail. Data analysis often becomes the bottleneck of automated inspections. Therefore,...
Focused ultrasound can successfully treat tumors by thermal ablation, but treatments using mechanical or electronic scanning of single foci can be prohibitively long. This study investigated a proposed approach to increase ablation efficiency by creating multiple foci as grating lobes of a coarse ultrasound aperture, then electronically scanning these grating lobes by applying phase rotations to shift...
We present a fully-populated 8×8 2D-phased array, capable of emitting directed air-coupled ultrasound at 40 kHz with λ/2-pitch size for zero grating lobes. In comparison to our previous work, in which we describe a 1D-phased array, we use 3D-printing to realize the wave guide structure. Besides the key idea to separate the vibrating from the acoustic aperture, the 3D-printing approach allows implementing...
Coherence-based methods have been shown to improve image quality by suppressing spurious lobes. However, when imaging a diffuse medium, such methods lead to a high variance of speckle amplitudes (i.e. granular appearance) which could limit their applicability for direct clinical imaging. The granular pattern may however be beneficial for speckle tracking echocardiography (STE), given the higher contrast...
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