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https://www.readbyqxmd.com/read/28327467/automated-detection-of-epileptic-ripples-in-meg-using-beamformer-based-virtual-sensors
#1
Carolina Migliorelli, Joan Alonso, Sergio Romero, Rafal Nowak, Antonio Russi, Miguel Mananas
OBJECTIVE: In epilepsy, high-frequency oscillations (HFOs) are considered events highly linked to the seizure onset zone (SOZ). The detection of HFOs in noninvasive signals such as scalp EEG and MEG is still a challenging task. The aim of this study was to automatize the detection of ripples in MEG signals reducing the high-frequency noise using beamformer-based virtual sensors (VS) and applying an automatic procedure exploring the time-frequency content of the detected events. APPROACH: 200 seconds of MEG signals and simultaneous iEEG were selected in nine patients with refractory epilepsy...
March 22, 2017: Journal of Neural Engineering
https://www.readbyqxmd.com/read/28320658/compressed-sensing-based-synthetic-transmit-aperture-imaging-validation-in-a-convex-array-configuration
#2
Jing Liu, Qiong He, Jianwen Luo
According to the linear acoustic theory, the channel data of a plane wave emitted by a linear array is a linear combination of the full dataset of synthetic transmit aperture (STA). Combining this relationship with compressed sensing (CS), a novel CS based ultrasound beamforming strategy, named compressed sensing based synthetic transmit aperture (CS-STA), was previously proposed to increase the frame rate of ultrasound imaging without sacrificing the image quality for a linear array. In this paper, assuming linear transfer function of pulse-echo ultrasound system, we derived and applied the theory of CS-STA for a slightly curved array and validated CS-STA in a convex array configuration...
March 14, 2017: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/28318887/multi-focus-beamforming-for-thermal-strain-imaging-using-a-single-ultrasound-linear-array-transducer
#3
Man M Nguyen, Xuan Ding, Steven A Leers, Kang Kim
Ultrasound-induced thermal strain imaging (TSI) has been used successfully to identify lipid- and water-based tissues in atherosclerotic plaques in some research settings. However, TSI faces several challenges to be realized in clinics. These challenges include motion artifacts and displacement tracking accuracy, as well as limited heating capability, which contributes to low thermal strain signal-to-noise ratio, and a limited field of view. Our goal was to address the challenge in heating tissue in TSI. Current TSI systems use separate heating and imaging transducers, which require physical alignment of the heating and imaging beams and result in a bulky setup that limits in vivo operation...
March 15, 2017: Ultrasound in Medicine & Biology
https://www.readbyqxmd.com/read/28282862/an-assessment-of-iterative-reconstruction-methods-for-sparse-ultrasound-imaging
#4
Solivan A Valente, Marcelo V W Zibetti, Daniel R Pipa, Joaquim M Maia, Fabio K Schneider
Ultrasonic image reconstruction using inverse problems has recently appeared as an alternative to enhance ultrasound imaging over beamforming methods. This approach depends on the accuracy of the acquisition model used to represent transducers, reflectivity, and medium physics. Iterative methods, well known in general sparse signal reconstruction, are also suited for imaging. In this paper, a discrete acquisition model is assessed by solving a linear system of equations by an ℓ 1 -regularized least-squares minimization, where the solution sparsity may be adjusted as desired...
March 8, 2017: Sensors
https://www.readbyqxmd.com/read/28268996/effects-of-phase-aberration-correction-methods-on-the-minimum-variance-beamformer
#5
Gustavo R Chau, Jeremy J Dahl, Roberto J Lavarello
The minimum variance (MV) beamformer is a method that has the potential to enhance the resolution and contrast of ultrasound images. However, it suffers from sensitivity to speed of sound errors and aberration. Although there have been several studies on the application of phase aberration correction (PAC) methods to conventional delay-and-sum (DAS) beamforming, the benefits of PAC methods in mitigating the effects of phase aberration in MV beamformed images are not well understood. A study of this type would be helpful in designing a robust beamformer based on PAC knowledge present in the literature...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28253687/application-of-acoustic-imaging-techniques-on-snowmobile-pass-by-noise
#6
Thomas Padois, Alain Berry
Snowmobile manufacturers invest important efforts to reduce the noise emission of their products. The noise sources of snowmobiles are multiple and closely spaced, leading to difficult source separation in practice. In this study, source imaging results for snowmobile pass-by noise are discussed. The experiments involve a 193-microphone Underbrink array, with synchronization of acoustic with video data provided by a high-speed camera. Both conventional beamforming and Clean-SC deconvolution are implemented to provide noise source maps of the snowmobile...
February 2017: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/28253650/blind-deconvolution-of-shipping-sources-in-an-ocean-waveguide
#7
Sung-Hoon Byun, Christopher M A Verlinden, Karim G Sabra
This paper investigates the applicability of a ray-based blind deconvolution (RBD) method for underwater acoustic sources of opportunity such as ships recorded on a receiver array. The RBD relies on first estimating the unknown phase of the random source by beamforming along a well-resolved ray path, and then matched-filtering each received signal using the knowledge of this random phase to estimate the full channel impulse responses (CIRs) between the unknown source and the array elements (up to an arbitrary time-shift) as well as recovering the radiated signal by the random source...
February 2017: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/28248655/4d-in-vivo-ultrafast-ultrasound-imaging-using-a-row-column-addressed-matrix-and-coherently-compounded-orthogonal-plane-waves
#8
Martin Flesch, Mathieu Pernot, Jean Provost, Guillaume Ferin, An Nguyen-Dinh, Mickael Tanter, Thomas Deffieux
4D ultrafast ultrasound imaging was recently shown using a 2D matrix (i.e., fully populated) connected to a 1024-channel ultrafast ultrasound scanner. In this study, we investigate the Row-Column Addressing (RCA) matrix approach, which allows a reduction of independent channels from N x N to N + N, with a dedicated beamforming strategy for ultrafast ultrasound imaging based on the coherent compounding of Orthogonal Plane Wave (OPW). OPW is based on coherent compounding of plane wave transmissions in one direction with receive beamforming along the orthogonal direction and its orthogonal companion sequence...
March 1, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28227206/effects-of-phase-aberration-correction-methods-on-the-minimum-variance-beamformer
#9
Gustavo R Chau, Jeremy J Dahl, Roberto J Lavarello, Gustavo R Chau, Jeremy J Dahl, Roberto J Lavarello, Gustavo R Chau, Roberto J Lavarello
The minimum variance (MV) beamformer is a method that has the potential to enhance the resolution and contrast of ultrasound images. However, it suffers from sensitivity to speed of sound errors and aberration. Although there have been several studies on the application of phase aberration correction (PAC) methods to conventional delay-and-sum (DAS) beamforming, the benefits of PAC methods in mitigating the effects of phase aberration in MV beamformed images are not well understood. A study of this type would be helpful in designing a robust beamformer based on PAC knowledge present in the literature...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28147604/large-region-acoustic-source-mapping-using-a-movable-array-and-sparse-covariance-fitting
#10
Shengkui Zhao, Cagdas Tuna, Thi Ngoc Tho Nguyen, Douglas L Jones
Large-region acoustic source mapping is important for city-scale noise monitoring. Approaches using a single-position measurement scheme to scan large regions using small arrays cannot provide clean acoustic source maps, while deploying large arrays spanning the entire region of interest is prohibitively expensive. A multiple-position measurement scheme is applied to scan large regions at multiple spatial positions using a movable array of small size. Based on the multiple-position measurement scheme, a sparse-constrained multiple-position vectorized covariance matrix fitting approach is presented...
January 2017: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/28147570/adaptive-and-compressive-matched-field-processing
#11
Kay L Gemba, William S Hodgkiss, Peter Gerstoft
Matched field processing is a generalized beamforming method that matches received array data to a dictionary of replica vectors in order to locate one or more sources. Its solution set is sparse since there are considerably fewer sources than replicas. Using compressive sensing (CS) implemented using basis pursuit, the matched field problem is reformulated as an underdetermined, convex optimization problem. CS estimates the unknown source amplitudes using the replica dictionary to best explain the data, subject to a row-sparsity constraint...
January 2017: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/28114609/the-effects-of-directional-processing-on-objective-and-subjective-listening-effort
#12
Erin M Picou, Travis M Moore, Todd A Ricketts
Purpose: The purposes of this investigation were (a) to evaluate the effects of hearing aid directional processing on subjective and objective listening effort and (b) to investigate the potential relationships between subjective and objective measures of effort. Method: Sixteen adults with mild to severe hearing loss were tested with study hearing aids programmed with 3 settings: omnidirectional, fixed directional, and bilateral beamformer. A dual-task paradigm and subjective ratings were used to assess objective and subjective listening effort, respectively, in 2 signal-to-noise ratios...
January 1, 2017: Journal of Speech, Language, and Hearing Research: JSLHR
https://www.readbyqxmd.com/read/28113662/beamforming-through-regularized-inverse-problems-in-ultrasound-medical-imaging
#13
Teodora Szasz, Adrian Basarab, Denis Kouame
Beamforming in ultrasound imaging has significant impact on the quality of the final image, controlling its resolution and contrast. Despite its low spatial resolution and contrast, delay-and-sum is still extensively used nowadays in clinical applications, due to its real-time capabilities. The most common alternatives are minimum variance method and its variants, which overcome the drawbacks of delay-and-sum, at the cost of higher computational complexity that limits its utilization in real-time applications...
September 13, 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/28113492/high-frame-rate-high-resolution-ultrasound-imaging-with-multi-line-transmission-and-filtered-delay-multiply-and-sum-beamforming
#14
Giulia Matrone, Alessandro Ramalli, Alessandro Savoia, Piero Tortoli, Giovanni Magenes
Multi-Line Transmission (MLT) was recently demonstrated as a valuable tool to increase the frame rate of ultrasound images. In this approach, the multiple beams that are simultaneously transmitted may determine cross-talk artifacts that are typically reduced, although not eliminated, by the use of Tukey apodization on both transmission and reception apertures, which unfortunately worsens the image lateral resolution. In this paper we investigate the combination, and related performance, of Filtered-Delay Multiply And Sum (F-DMAS) beamforming with MLT for high frame-rate ultrasound imaging...
October 4, 2016: IEEE Transactions on Medical Imaging
https://www.readbyqxmd.com/read/28113371/synthetic-aperture-ultrasound-fourier-beamformation-using-virtual-sources
#15
Elahe Moghimirad, Carlos A Villagomez-Hoyos, Ali Mahloojifar, Babak Mohammadzadeh Asl, Jorgen Jensen
An efficient Fourier beamformation algorithm is presented for multistatic synthetic aperture ultrasound imaging using virtual sources (FBV). The concept is based on the frequency domain wavenumber algorithm from radar and sonar and is extended to a multi-element transmit/receive configuration using virtual sources. Window functions are used to extract the azimuth processing bandwidths and weight the data to reduce sidelobes in the final image. Field II simulated data and SARUS measured data are used to evaluate the results in terms of point spread function, resolution, contrast, SNR, and processing time...
September 7, 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/28068874/short-lag-spatial-coherence-ultrasound-imaging-with-adaptive-synthetic-transmit-aperture-focusing
#16
Jinxin Zhao, Yuanyuan Wang, Jinhua Yu, Wei Guo, Shun Zhang, Saeid Aliabadi
The short-lag spatial coherence (SLSC) imaging has been demonstrated to be advantageous over the traditional B-mode ultrasound imaging. With focused scanning beams, the SLSC imaging has an excellent performance in clutter reduction and lesion detection, especially in the low signal-to-noise ratio (SNR) scenarios. The synthetic aperture (SA) imaging is an appropriate mode for the SLSC imaging as the dynamic transmit focusing could keep a good focusing quality at any depth. However, the SLSC image may still suffer a bad resolution performance when a low lag value is used in the coherence summation to ensure the contrast enhancement...
January 1, 2017: Ultrasonic Imaging
https://www.readbyqxmd.com/read/28040049/ambient-noise-correlations-on-a-mobile-deformable-array
#17
Perry Naughton, Philippe Roux, Riley Yeakle, Curt Schurgers, Ryan Kastner, Jules S Jaffe, Paul L D Roberts
This paper presents a demonstration of ambient acoustic noise processing on a set of free floating oceanic receivers whose relative positions vary with time. It is shown that it is possible to retrieve information that is relevant to the travel time between the receivers. With thousands of short time cross-correlations (10 s) of varying distance, it is shown that on average, the decrease in amplitude of the noise correlation function with increased separation follows a power law. This suggests that there may be amplitude information that is embedded in the noise correlation function...
December 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/28040045/compressive-spherical-beamforming-for-localization-of-incipient-tip-vortex-cavitation
#18
Youngmin Choo, Woojae Seong
Noises by incipient propeller tip vortex cavitation (TVC) are generally generated at regions near the propeller tip. Localization of these sparse noises is performed using compressive sensing (CS) with measurement data from cavitation tunnel experiments. Since initial TVC sound radiates in all directions as a monopole source, a sensing matrix for CS is formulated by adopting spherical beamforming. CS localization is examined with known source acoustic measurements, where the CS estimated source position coincides with the known source position...
December 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/28011340/depth-of-field-enhancement-in-filtered-delay-multiply-and-sum-beamformed-images-using-synthetic-aperture-focusing
#19
Giulia Matrone, Alessandro Stuart Savoia, Giosuè Caliano, Giovanni Magenes
The Synthetic Aperture Focusing (SAF) technique makes it possible to achieve a higher and more uniform quality of ultrasound images throughout depth, as if both transmit and receive dynamic focusing were applied. In this work we combine a particular implementation of SAF, called Synthetic Transmit Aperture (STA) technique, in which a single element in turn transmits and all the array elements receive the ultrasound wave, with the Filtered-Delay Multiply and Sum (F-DMAS) non-linear beamforming algorithm that we presented in a previous paper...
March 2017: Ultrasonics
https://www.readbyqxmd.com/read/27939788/combined-phase-screen-aberration-correction-and-minimum-variance-beamforming-in-medical-ultrasound
#20
Mahsa Sotoodeh Ziksari, Babak Mohammadzadeh Asl
In recent years, applying adaptive beamforming to ultrasound imaging improves image quality in terms of resolution and contrast. One of the best adaptive beamformers in this field is the minimum variance (MV) beamformer which presents better resolution and edge definition compared to the traditional delay-and-sum (DAS) beamformer. However, in real situations, sound-velocity inhomogeneities cause phase aberration which leads to ambiguity in targets' location and degradation in resolution. This effect is a fundamental obstacle to utilize advantages of MV beamformer, although, in aberrating medium MV beamformer results in better performance compared to DAS...
March 2017: Ultrasonics
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