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Beamforming noise

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https://www.readbyqxmd.com/read/28702346/automatic-detection-and-visualisation-of-meg-ripple-oscillations-in-epilepsy
#1
Nicole van Klink, Frank van Rosmalen, Jukka Nenonen, Sergey Burnos, Liisa Helle, Samu Taulu, Paul Lawrence Furlong, Maeike Zijlmans, Arjan Hillebrand
High frequency oscillations (HFOs, 80-500 Hz) in invasive EEG are a biomarker for the epileptic focus. Ripples (80-250 Hz) have also been identified in non-invasive MEG, yet detection is impeded by noise, their low occurrence rates, and the workload of visual analysis. We propose a method that identifies ripples in MEG through noise reduction, beamforming and automatic detection with minimal user effort. We analysed 15 min of presurgical resting-state interictal MEG data of 25 patients with epilepsy. The MEG signal-to-noise was improved by using a cross-validation signal space separation method, and by calculating ~ 2400 beamformer-based virtual sensors in the grey matter...
2017: NeuroImage: Clinical
https://www.readbyqxmd.com/read/28692968/intravascular-ultrasound-imaging-with-virtual-source-synthetic-aperture-vssa-focusing-and-coherence-factor-weighting-cfw
#2
Mingyue Yu, Yang Li, Teng Ma, K Kirk Shung, Qifa Zhou
Intravascular ultrasound (IVUS) has been frequently used for coronary artery imaging clinically. More importantly, IVUS is the fundamental image modality for most advanced multimodality intravascular imaging techniques since it provides a more comprehensive picture of vessel anatomy on which other imaging data can be superimposed. However, image quality in the deeper region is poor because of the downgraded lateral resolution and contrast-to-noise ratio. In this study, we report on the application of an ultrasound beamforming method that combines virtual source synthetic aperture (VSSA) focusing and coherence factor weighting (CFW) to improve the IVUS image quality...
July 4, 2017: IEEE Transactions on Medical Imaging
https://www.readbyqxmd.com/read/28675376/model-based-bayesian-signal-extraction-algorithm-for-peripheral-nerves
#3
Thomas Eggers, Yazan M Dweiri, Grant McCallum, Dominique M Durand
Multi-channel cuff electrodes have recently been investigated for extracting fascicular-level motor commands from mixed neural recordings. Such signals could provide volitional, intuitive control over a robotic prosthesis for amputee patients. Recent work has demonstrated success in extracting these signals in acute and chronic preparations using spatial filtering techniques. These extracted signals, however, had low signal-to-noise ratios and thus limited their utility to binary classification. In this work a new algorithm is proposed which combines previous source localization approaches to create a model based method which operates in real time...
July 4, 2017: Journal of Neural Engineering
https://www.readbyqxmd.com/read/28664331/benefit-of-the-ultrazoom-beamforming-technology-in-noise-in-cochlear-implant-users
#4
Isabelle Mosnier, Nathalie Mathias, Jonathan Flament, Dorith Amar, Amelie Liagre-Callies, Stephanie Borel, Emmanuèle Ambert-Dahan, Olivier Sterkers, Daniele Bernardeschi
The objectives of the study were to demonstrate the audiological and subjective benefits of the adaptive UltraZoom beamforming technology available in the Naída CI Q70 sound processor, in cochlear-implanted adults upgraded from a previous generation sound processor. Thirty-four adults aged between 21 and 89 years (mean 53 ± 19) were prospectively included. Nine subjects were unilaterally implanted, 11 bilaterally and 14 were bimodal users. The mean duration of cochlear implant use was 7 years (range 5-15 years)...
June 29, 2017: European Archives of Oto-rhino-laryngology
https://www.readbyqxmd.com/read/28627331/dynamic-transmit-receive-beamforming-by-spatial-matched-filtering-for-ultrasound-imaging-with-plane-wave-transmission
#5
Yuling Chen, Yang Lou, Jesse Yen
During conventional ultrasound imaging, the need for multiple transmissions for one image and the time of flight for a desired imaging depth limit the frame rate of the system. Using a single plane wave pulse during each transmission followed by parallel receive processing allows for high frame rate imaging. However, image quality is degraded because of the lack of transmit focusing. Beamforming by spatial matched filtering (SMF) is a promising method which focuses ultrasonic energy using spatial filters constructed from the transmit-receive impulse response of the system...
July 2017: Ultrasonic Imaging
https://www.readbyqxmd.com/read/28618818/passive-bottom-reflection-loss-estimation-using-ship-noise-and-a-vertical-line-array
#6
Lanfranco Muzi, Martin Siderius, Christopher M Verlinden
An existing technique for passive bottom-loss estimation from natural marine surface noise (generated by waves and wind) is adapted to use noise generated by ships. The original approach-based on beamforming of the noise field recorded by a vertical line array of hydrophones-is retained; however, additional processing is needed in order for the field generated by a passing ship to show features that are similar to those of the natural surface-noise field. A necessary requisite is that the ship position, relative to the array, varies over as wide a range of steering angles as possible, ideally passing directly over the array to ensure coverage of the steepest angles...
June 2017: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/28604358/dual-stage-beamforming-in-absence-of-front-end-receive-focusing
#7
Deep Bera, Johan Bosch, Martin Verweij, Nico De Jong, Hendrik Vos
Ultrasound front-end receive designs for miniature, wireless, and/or matrix transducers might be simplified considerably by direct element summation in receive. In this paper we develop a dual-stage beamforming technique which is able to produce a high quality image from scanlines that are produced with focused transmit, and simple summation in receive (no delays). We call this Non-Delayed Sequential Beamforming (NDSB). In the first stage, low-resolution RF scanlines are formed by simple summation of element signals from a running sub-aperture...
June 12, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28603452/cross-correlation-beamforming
#8
Elmer Ruigrok, Steven Gibbons, Kees Wapenaar
An areal distribution of sensors can be used for estimating the direction of incoming waves through beamforming. Beamforming may be implemented as a phase-shifting and stacking of data recorded on the different sensors (i.e., conventional beamforming). Alternatively, beamforming can be applied to cross-correlations between the waveforms on the different sensors. We derive a kernel for beamforming cross-correlated data and call it cross-correlation beamforming (CCBF). We point out that CCBF has slightly better resolution and aliasing characteristics than conventional beamforming...
2017: Journal of Seismology
https://www.readbyqxmd.com/read/28599535/experimental-investigation-of-trailing-edge-noise-from-stationary-and-rotating-airfoils
#9
Branko Zajamsek, Con J Doolan, Danielle J Moreau, Jeoffrey Fischer, Zebb Prime
Trailing edge noise from stationary and rotating NACA 0012 airfoils is characterised and compared with a noise prediction based on the semi-empirical Brooks, Pope, and Marcolini (BPM) model. The NACA 0012 is symmetrical airfoil with no camber and 12% thickness to chord length ratio. Acoustic measurements were conducted in an anechoic wind tunnel using a stationary NACA 0012 airfoil at 0° pitch angle. Airfoil self-noise emissions from rotating NACA 0012 airfoils mounted at 0° and 10° pitch angles on a rotor-rig are studied in an anechoic room...
May 2017: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/28598386/a-noise-removal-method-for-uniform-circular-arrays-in-complex-underwater-noise-environments-with-low-snr
#10
Huijun Xia, Kunde Yang, Yuanliang Ma, Yong Wang, Yaxiong Liu
Generally, many beamforming methods are derived under the assumption of white noise. In practice, the actual underwater ambient noise is complex. As a result, the noise removal capacity of the beamforming method may be deteriorated considerably. Furthermore, in underwater environment with extremely low signal-to-noise ratio (SNR), the performances of the beamforming method may be deteriorated. To tackle these problems, a noise removal method for uniform circular array (UCA) is proposed to remove the received noise and improve the SNR in complex noise environments with low SNR...
June 9, 2017: Sensors
https://www.readbyqxmd.com/read/28574349/specular-beamforming
#11
Alfonso Rodriguez-Molares, Ali Fatemi, Lasse Lovstakken, Hans Torp
Acoustically hard objects such as bones, needles, or catheters are poorly visualized in conventional ultrasound images. These objects behave like acoustic mirrors and reflect sound in specific directions. Soft tissue and diffusive reflectors scatter sound in a broad range of directions. Conventional delayand- sum (DAS) beamforming is based on the assumption of a purely scattering domain with relatively weak reflectivity. We present an adaptive beamforming technique that takes into account the physics of specular reflection...
May 26, 2017: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
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
#12
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
#13
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
#14
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
#15
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
#16
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
#17
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
#18
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
#19
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
#20
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
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