IEEE transactions on ultrasonics, ferroelectrics, and frequency control
-
IEEE Trans Ultrason Ferroelectr Freq Control · Oct 2020
Ultrafast Phased-Array Imaging Using Sparse Orthogonal Diverging Waves.
We present a new transmit pulse encoding scheme for ultrafast phased-array imaging called sparse orthogonal diverging wave imaging (SODWI). In SODWI, Hadamard encoding is used to selectively invert transmit pulse phases beamformed with a diverging wave delay profile. This approach has the advantage of delivering energy to a much wider field of view than conventional Hadamard-encoded multielement synthetic transmit aperture (HMSTA), making it more suitable for phased-array applications. ⋯ SODWI is then compared with a variety of beamforming schemes for phased-array applications, including HMSTA, STEDI-HMSTA, diverging wave imaging (DWI), synthetic aperture (SA), and focused imaging. We present the results by implementing this technique on a 64-channel custom beamforming platform with a 40-MHz phased array. When a full set of codes is used, SODWI outperforms focused imaging contrast and SNR by 2.7 and 1.8 dB in addition to an 8× increase in frame rate, respectively.
-
IEEE Trans Ultrason Ferroelectr Freq Control · Mar 2018
A Column-Row-Parallel Ultrasound Imaging Architecture for 3D Plane-wave Imaging and Tx 2nd-Order Harmonic Distortion (HD2) Reduction.
We propose a Column-Row-Parallel imaging frontend architecture for integrated and low-power 3D medical ultrasound imaging. The Column-Row-Parallel architecture offers linear-scaling interconnection, acquisition and programming time with row-by-row or column-by-column operations, while supporting volumetric imaging functionality and fault-tolerance against possible transducer element defects with per-element controls. The combination of column-parallel selection logic, row-parallel selection logic, and per-element selection logic reaches a balance between flexible imaging aperture definition and manageable imaging data / control interface to a 2D array. ⋯ At a hypothetically scaled up 64x64 array size, the frame rate can still be kept at 31.2 Hz for a volume of 40mm in both azimuth and elevation, 150mm in depth. An interleaved checker board pattern with in-phase (I) and quadrature (Q) excitations is also demonstrated for reducing CMUT second harmonic distortion (HD2) emission by up to 25 dB at the loss of 3 dB fundamental energy reduction. The method reduces nonlinear effects from both transducers and circuits and is a wide band technique that is applicable to arbitrary pulse shapes.
-
IEEE Trans Ultrason Ferroelectr Freq Control · Dec 2016
Functional Transcranial Doppler Ultrasound for Measurement of Hemispheric Lateralization During Visual Memory and Visual Search Cognitive Tasks.
Functional transcranial Doppler ultrasound (fTCD) is a noninvasive sensing modality that measures cerebral blood flow velocity (CBFV) with high temporal resolution. CBFV change is correlated to changes in cerebral oxygen uptake, enabling fTCD to measure brain activity and lateralization with high accuracy. However, few studies have examined the relationship of CBFV change during visual search and visual memory tasks. ⋯ The results showed significant lateralization ( ) of the visual memory and visual search tasks, with memory reaching lateralization of 1.6% and search reaching lateralization of 0.5%, suggesting that search is more right lateralized (and therefore may be related to "holistic" or global perception) and memory is more left lateralized (and therefore may be related to local perception). This method could be used to compare cerebral activity for any related cognitive tasks as long as the same stimulus is used in all tasks. The protocol is straightforward and the equipment is inexpensive, introducing a low-cost high temporal resolution technique to further study lateralization of the brain.
-
IEEE Trans Ultrason Ferroelectr Freq Control · Dec 2015
In Vivo application and localization of transcranial focused ultrasound using dual-mode ultrasound arrays.
Focused ultrasound (FUS) has been proposed for a variety of transcranial applications, including neuromodulation, tumor ablation, and blood-brain barrier opening. A flurry of activity in recent years has generated encouraging results demonstrating its feasibility in these and other applications. To date, monitoring of FUS beams has been primarily accomplished using MR guidance, where both MR thermography and elastography have been used. ⋯ The in vivo experiments were designed to demonstrate the ability of the DMUA to apply, monitor, and localize subtherapeutic tFUS patterns that could be beneficial in transient blood-brain barrier opening. The results show that although the DMUA focus is degraded due to the propagation through the skull, it still produces localized heating effects within a sub-millimeter volume. In addition, DMUA transcranial echo data from brain tissue allow for reliable estimation of temperature change.
-
IEEE Trans Ultrason Ferroelectr Freq Control · Oct 2015
Increasing specificity of contrast-enhanced ultrasound imaging using the interaction of quasi counter-propagating wavefronts: a proof of concept.
Detection methods implemented in present clinical ultrasound scanners for contrast-enhanced ultrasound imaging show high sensitivity but a rather poor specificity due to pseudo-enhancement (false detection of contrast agent) produced by nonlinear wave propagation. They all require linear ultrasound propagation to detect nonlinear scattering of contrast agent microbubbles. Even at low transmit pressure, nonlinear wave propagation occurs in regions perfused with contrast agent because contrast agent microbubbles can dramatically enhance the nonlinear elastic behavior of the medium. ⋯ At a given depth, increasing the distance between the two transmitting elements increases the angle describing the propagation directions of the two wavefronts. As a result, the nonlinear interaction between the two broadcasted waves is reduced. We show experimentally that increasing the distance between the transmitting elements from 0.6 to 24 mm reduces the amplitude of the pseudoenhancement at the far wall of the vessel relative to true contrast signal amplitude in the vessel by 12 dB, therefore improving specificity in the contrast-enhanced image.