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https://www.readbyqxmd.com/read/28479475/the-impact-of-meg-source-reconstruction-method-on-source-space-connectivity-estimation-a-comparison-between-minimum-norm-solution-and-beamforming
#1
Ana-Sofía Hincapié, Jan Kujala, Jérémie Mattout, Annalisa Pascarella, Sebastien Daligault, Claude Delpuech, Domingo Mery, Diego Cosmelli, Karim Jerbi
Despite numerous important contributions, the investigation of brain connectivity with magnetoencephalography (MEG) still faces multiple challenges. One critical aspect of source-level connectivity, largely overlooked in the literature, is the putative effect of the choice of the inverse method on the subsequent cortico-cortical coupling analysis. We set out to investigate the impact of three inverse methods on source coherence detection using simulated MEG data. To this end, thousands of randomly located pairs of sources were created...
May 4, 2017: NeuroImage
https://www.readbyqxmd.com/read/28463190/improved-contrast-enhanced-power-doppler-using-a-coherence-based-estimator
#2
Charles Tremblay-Darveau, Avinoam Bar-Zion, R Williams, Paul Sheeran, Laurent Milot, Thanasis Loupas, Dan Adam, Matthew Bruce, Peter Burns
While plane-wave imaging can improve the performance of power Doppler by enabling much longer ensembles than systems using focused beams, the long-ensemble averaging of the zero-lag autocorrelation R(0) estimates does not directly decrease the mean noise level, but only decreases its variance. Spatial variation of the noise due to the time-gain compensation and the received beamforming aperture ultimately limits sensitivity. In this paper, we demonstrate that the performance of power Doppler imaging can be improved by leveraging the higher lags of the autocorrelation (e...
April 28, 2017: IEEE Transactions on Medical Imaging
https://www.readbyqxmd.com/read/28458062/experimental-performance-assessment-of-the-sub-band-minimum-variance-beamformer-for-ultrasound-imaging
#3
Konstantinos Diamantis, Alan Greenaway, Tom Anderson, Jørgen Arendt Jensen, Vassilis Sboros
Recent progress in adaptive beamforming techniques for medical ultrasound has shown that current resolution limits can be surpassed. One method of obtaining improved lateral resolution is the Minimum Variance (MV) beamformer. The frequency domain implementation of this method effectively divides the broadband ultrasound signals into sub-bands (MVS) to conform with the narrow-band assumption of the original MV theory. This approach is investigated here using experimental Synthetic Aperture (SA) data from wire and cyst phantoms...
April 21, 2017: Ultrasonics
https://www.readbyqxmd.com/read/28432914/adaptive-optimization-of-ultrasound-beamforming-sound-velocity-using-sub-aperture-differential-phase-gradient
#4
Che-Chou Shen, Hsiao-Chi Yang
Ultrasound array imaging systems rely on a presumed beamforming sound velocity to calculate the time compensation of each element for receive focusing. The mismatch between the tissue sound velocity and the beamforming sound velocity can degrade the focusing quality due to loss of phase coherence. Since the tissue sound velocity cannot be known in prior, an adaptive optimization of beamforming sound velocity is required to improve the image quality. Differential phase gradient of channel data is proposed to estimate the optimal sound velocity for beamforming...
April 12, 2017: Ultrasonics
https://www.readbyqxmd.com/read/28394290/combining-dcqgmp-based-sparse-decomposition-and-mpdr-beamformer-for-multi-type-interferences-mitigation-for-gnss-receivers
#5
Qiang Guo, Liangang Qi
In the coexistence of multiple types of interfering signals, the performance of interference suppression methods based on time and frequency domains is degraded seriously, and the technique using an antenna array requires a large enough size and huge hardware costs. To combat multi-type interferences better for GNSS receivers, this paper proposes a cascaded multi-type interferences mitigation method combining improved double chain quantum genetic matching pursuit (DCQGMP)-based sparse decomposition and an MPDR beamformer...
April 10, 2017: Sensors
https://www.readbyqxmd.com/read/28391187/double-stage-delay-multiply-and-sum-beamforming-algorithm-application-to-linear-array-photoacoustic-imaging
#6
Moein Mozaffarzadeh, Ali Mahloojifar, Mahdi Orooji, Saba Adabi, Mohammadreza Nasiriavanaki
Photoacoustic imaging (PAI) is an emerging medical imaging modality capable of providing high spatial resolution of Ultrasound (US) imaging and high contrast of optical imaging. Delay-and-Sum (DAS) is the most common beamforming algorithm in PAI. However, using DAS beamformer leads to low resolution images and considerable contribution of offaxis signals. A new paradigm namely Delay-Multiply-and-Sum (DMAS), which was originally used as a reconstruction algorithm in confocal microwave imaging, was introduced to overcome the challenges in DAS...
April 5, 2017: IEEE Transactions on Bio-medical Engineering
https://www.readbyqxmd.com/read/28378012/computational-acoustic-beamforming-for-noise-source-identification-for-small-wind-turbines
#7
Ping Ma, Fue-Sang Lien, Eugene Yee
This paper develops a computational acoustic beamforming (CAB) methodology for identification of sources of small wind turbine noise. This methodology is validated using the case of the NACA 0012 airfoil trailing edge noise. For this validation case, the predicted acoustic maps were in excellent conformance with the results of the measurements obtained from the acoustic beamforming experiment. Following this validation study, the CAB methodology was applied to the identification of noise sources generated by a commercial small wind turbine...
2017: International Scholarly Research Notices
https://www.readbyqxmd.com/read/28372122/coherence-factor-and-wiener-postfilter-in-synthetic-aperture-ultrasound-imaging
#8
Jinxin Zhao, Yuanyuan Wang, Wei Guo, Jinhua Yu
The coherence factor (CF) and Wiener postfilter methods have been proposed as effective approaches for reducing the output noise of the delay-and-sum (DAS) beamformer in ultrasound imaging. The theoretical framework between them was also established. However, past researches about the CF and Wiener postfilter methods mainly focused on the summation of an array signal. This paper analyzes the CF and Wiener postfilter in the synthetic aperture (SA) imaging mode, where two-dimensional echo data are recorded. Different CF definitions in the SA imaging are first given and the corresponding Wiener postfilter methods are then proposed, including a Wiener postfilter especially for the SA imaging, named as WienerSA...
March 2017: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/28372093/generalized-sidelobe-canceller-beamforming-method-for-ultrasound-imaging
#9
Ping Wang, Na Li, Han-Wu Luo, Yong-Kun Zhu, Shi-Gang Cui
A modified generalized sidelobe canceller (IGSC) algorithm is proposed to enhance the resolution and robustness against the noise of the traditional generalized sidelobe canceller (GSC) and coherence factor combined method (GSC-CF). In the GSC algorithm, weighting vector is divided into adaptive and non-adaptive parts, while the non-adaptive part does not block all the desired signal. A modified steer vector of the IGSC algorithm is generated by the projection of the non-adaptive vector on the signal space constructed by the covariance matrix of received data...
March 2017: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/28351747/improved-contrast-for-high-frame-rate-imaging-using-coherent-compounding-combined-with-spatial-matched-filtering
#10
Yang Lou, Jesse T Yen
The concept of high frame rate ultrasound imaging (typically greater than 1000 frames per second) has inspired new fields of clinical applications for ultrasound imaging such as fast cardiovascular imaging, fast Doppler imaging and real-time 3D imaging. Coherent plane-wave compounding is a promising beamforming technique to achieve high frame rate imaging. By combining echoes from plane waves with different angles, dynamic transmit focusing is efficiently accomplished at all points in the image field. Meanwhile, the image frame rate can still be kept at a high level...
March 20, 2017: Ultrasonics
https://www.readbyqxmd.com/read/28327467/automated-detection-of-epileptic-ripples-in-meg-using-beamformer-based-virtual-sensors
#11
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
#12
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
#13
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...
June 2017: Ultrasound in Medicine & Biology
https://www.readbyqxmd.com/read/28282862/an-assessment-of-iterative-reconstruction-methods-for-sparse-ultrasound-imaging
#14
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
#15
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
#16
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
#17
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
#18
M Flesch, M Pernot, J Provost, G Ferin, A Nguyen-Dinh, M Tanter, T 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  ×  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
#19
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
#20
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
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