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This contribution is concerned with a technique to precisely measure the physical dimensions of flaws in solid specimen by pulse-echo mode acoustic microscopy. We have implemented a synthetic aperture focusing technique (SAFT), which is based on a semi-numerical simulation approach (SIRFEM). In acoustic microscopy, one normally applies single-element transducers with center frequencies above 10MHz...
The new application of ultrasonic imaging to transient elastography has triggered the emergence of high frame-rate imaging. Using plane wave excitation (PWE), a single insonification is sufficient to form an image; thus PWE is one of the methods for achieving high frame-rate imaging. However, due to the lack of transmit focusing, the signal-to-noise-ratio (SNR), contrast, and spatial resolution of...
We present a Fourier domain beamforming method for ultrafast pulse-echo imaging that significantly reduces the number of acquired samples. In its basic form, our proposed method combines the low-rate in-phase and quadrature sampling of the received analog radio frequency (RF) signals and the electronic receive focusing in the temporal Fourier domain. Using both synthetic and in vivo measurement data,...
The speckle texture in ultrasound images is inherent to the coherent beamforming process for diffuse targets and limits the detectability of low contrast targets. Speckle compounding takes advantage of the limited spatial and frequency correlation of speckle by incoherently averaging multiple realizations to reduce the variance and smooth the background texture. Conventionally, spatial compounding...
Ultrasonic non-destructive testing (UNDT) is often used for detecting the qualities of pipelines and axles by circular scanning. Confined by the mechanical precision, circular scanning has an eccentricity to the center axis of cylinder in industrial detection. However, most synthetic aperture focusing techniques (SAFT) employed to improve the lateral resolution of ultrasound images are established...
We suggest an experimental realization for a new concept of chaotic transducer based on memristors and specifically devoted to the optimization of ultrasonic excitation involved in nonlinear time reversal based ultrasonic imaging. The design utilizes hysteretic properties of a Knowm Inc memristor, considered as the new key electronic component used in mimicking elementary cells plasticity and biological...
The focusing of ultrasound in the Non Destructive Testing of complex materials needs to be improved. Despite the considerable interest attracted by the Nonlinear Elastic Waves Spectroscopy (NEWS) and nonlinear Time Reversal (TR) techniques and the resulting advances in recent years, several aspects related to the use of modern signal processing tools remain to be addressed. We present here the concept...
To simplify the system complexity of three-dimensional (3-D) ultrasound imaging system and reduce the cost, microbeamforming (MBF) approach has been proposed to reduce the interconnections between the ultrasound probe and the back-end digital system. However, focusing delay errors are still present, which broadens the main lobe and increases the side-lobe and grating-lobe levels, which together degrade...
The spot size of HIFU lesion depends on many parameters like size of the transducer, frequency of operation, sonication time etc. A recently developed CMUT based HIFU application for corneal keratoplasty require high localized temperature rise within a very small confined area as short as 300–500µm in length. To simplify the electrical connection requirements for this relatively small sized array,...
Plane-wave ultrasound imaging allows achieving very high frame rates in the order of kHz, as an entire image can be acquired using a single plane-wave transmission. Unfortunately, image quality is significantly reduced by the lack of transmit focusing. To mitigate this problem, the frames acquired by transmitting several plane waves with different steering angles can be coherently compounded, but...
In this work, the total focusing method is used to image defects in a high density polyethylene pipe. The viscoelastic attenuation of this material corrupts the images with a high electronic noise. To improve the image quality, the decomposition of the time reversal operator method is combined with spatial Walsh-Hadamard coded transmissions before calculating the images.
Phased Array (PA) uses a single focus in emission and Dynamic Depth Focusing (DDF) in reception, while Total Focusing Method (TFM) focuses every image pixel in emission and in reception. By contrast, TFM lacks the A-scan information, which is standard in PA and can be very useful for evaluation. Another issue common to both techniques is the difficulty associated with two media propagation and unknown...
Experimental 3-D vector flow estimates obtained with a 62+62 2-D row-column (RC) array with integrated apodization are presented. A transverse oscillation (TO) velocity estimator is implemented on a 3.0 MHz RC array, to yield real-time 3-D vector flow in a cross-sectional scan plane at 750 frames per second. The method is validated in a straight-vessel phantom (Ø = 8 mm) connected to a flow pump capable...
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