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Noise reduction

Rachel J Anderson, Stephen A Dewhurst, Graham M Dean
Two experiments used a dual task methodology to investigate the role of visual imagery and executive resources in the retrieval of specific autobiographical memories. In Experiment 1, dynamic visual noise led to a reduction in the number of specific memories retrieved in response to both high and low imageability cues, but did not affect retrieval times. In Experiment 2, irrelevant pictures reduced the number of specific memories but only in response to low imageability cues. Irrelevant pictures also increased response times to both high and low imageability cues...
February 16, 2017: Consciousness and Cognition
Zhen-Qun Yang, Xiao-Yong Wei, Zhang Yi, Gerald Friedland
In this paper, we have proposed a novel method which utilizes the contextual relationship among visual words for reducing the Quantization errors in near-duplicate image retrieval (NDR). Instead of following the track of conventional NDR techniques which usually search new solutions by borrowing ideas from the text domain, we propose to model the problem back to image domain, which results in a more natural way of solution search. The idea of the proposed method is to construct a context graph that encapsulates the contextual relationship within an image and treat the graph as a pseudo-image, so that classical image filters can be adopted to reduce the mismapped visual words which are contextually inconsistent with others...
February 15, 2017: IEEE Transactions on Image Processing: a Publication of the IEEE Signal Processing Society
Bumsub Ham, Minsu Cho, Jean Ponce
Filtering images using a guidance signal, a process called guided or joint image filtering, has been used in various tasks in computer vision and computational photography, particularly for noise reduction and joint upsampling. This uses an additional guidance signal as a structure prior, and transfers the structure of the guidance signal to an input image, restoring noisy or altered image structure. The main drawbacks of such a data-dependent framework are that it does not consider structural differences between guidance and input images, and that it is not robust to outliers...
February 14, 2017: IEEE Transactions on Pattern Analysis and Machine Intelligence
S E de Graaf, A A Adamyan, T Lindström, D Erts, S E Kubatkin, A Ya Tzalenchuk, A V Danilov
An on-chip electron spin resonance technique is applied to reveal the nature and origin of surface spins on Al_{2}O_{3}. We measure a spin density of 2.2×10^{17}  spins/m^{2}, attributed to physisorbed atomic hydrogen and S=1/2 electron spin states on the surface. This is direct evidence for the nature of spins responsible for flux noise in quantum circuits, which has been an issue of interest for several decades. Our findings open up a new approach to the identification and controlled reduction of paramagnetic sources of noise and decoherence in superconducting quantum devices...
February 3, 2017: Physical Review Letters
Yothin Rakvongthai, Frederic Fahey, Korn Borvorntanajanya, Supatporn Tepmongkol, Usanee Vutrapongwatana, Katherine Zukotynski, Georges El Fakhri, Jinsong Ouyang
PURPOSE: To improve the performance for localizing epileptic foci, we have developed a joint ictal/inter-ictal SPECT reconstruction method in which ictal and inter-ictal SPECT projections are simultaneously reconstructed to obtain the differential image. METHODS: We have developed a SPECT reconstruction method that jointly reconstructs ictal and inter-ictal SPECT projection data. We performed both phantom and patient studies to evaluate the performance of our joint method for epileptic foci localization as compared with the conventional subtraction method in which the differential image is obtained by subtracting the inter-ictal image from the co-registered ictal image...
February 16, 2017: Medical Physics
Vinal Lakhani, Timothy C Elston
The ability to detect a chemical gradient is fundamental to many cellular processes. In multicellular organisms gradient sensing plays an important role in many physiological processes such as wound healing and development. Unicellular organisms use gradient sensing to move (chemotaxis) or grow (chemotropism) towards a favorable environment. Some cells are capable of detecting extremely shallow gradients, even in the presence of significant molecular-level noise. For example, yeast have been reported to detect pheromone gradients as shallow as 0...
February 16, 2017: PLoS Computational Biology
Ashok Mondal, Ishan Saxena, Hong Tang, Poulami Banerjee
The main difficulty encountered in interpretation of cardiac sound is interference of noise. The contaminated noise obscures the relevant information which are useful for recognition of heart diseases. The unwanted signals are produced mainly by lungs and surrounding environment. In this paper, a novel heart sound de-noising technique has been introduced based on a combined framework of wavelet packet transform (WPT) and singular value decomposition (SVD). The most informative node of wavelet tree is selected on the criteria of mutual information measurement...
February 13, 2017: IEEE Journal of Biomedical and Health Informatics
Mengye Lyu, Yilong Liu, Victor B Xie, Yanqiu Feng, Hua Guo, Ed X Wu
PROPELLER technique is widely used in MRI examinations for being motion insensitive, but it prolongs scan time and is restricted mainly to T2 contrast. Parallel imaging can accelerate PROPELLER and enable more flexible contrasts. Here, we propose a multi-step joint-blade (MJB) SENSE reconstruction to reduce the noise amplification in parallel imaging accelerated PROPELLER. MJB SENSE utilizes the fact that PROPELLER blades contain sharable information and blade-combined images can serve as regularization references...
February 16, 2017: Scientific Reports
R H H Wellenberg, M F Boomsma, J A C van Osch, A Vlassenbroek, J Milles, M A Edens, G J Streekstra, C H Slump, M Maas
OBJECTIVE: To compare quantitative measures of image quality, in terms of CT number accuracy, noise, signal-to-noise-ratios (SNRs), and contrast-to-noise ratios (CNRs), at different dose levels with filtered-back-projection (FBP), iterative reconstruction (IR), and model-based iterative reconstruction (MBIR) alone and in combination with orthopedic metal artifact reduction (O-MAR) in a total hip arthroplasty (THA) phantom. MATERIALS AND METHODS: Scans were acquired from high- to low-dose (CTDIvol: 40...
February 15, 2017: Skeletal Radiology
Xingfeng Shao, Yi Wang, Steen Moeller, Danny J J Wang
PURPOSE: To present a constrained slice-dependent (CSD) background-suppression (BS) scheme in 2D arterial spin labeling (ASL) using simultaneous multislice acquisition with blipped-CAIPIRINHA (controlled aliasing in parallel imaging results in higher acceleration). METHODS: Background suppression for 2D acquisition is challenging because of the multiple nulling points required for sequential slice readout. Constrained slice-dependent BS exploits the simultaneous multislice technique to reduce the readout duration, and uses slice-dependent premodulation pulses to achieve BS across slice groups...
February 15, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Fangfang Zhang, Junjie Ma, Junji Watanabe, Jinlong Tang, Huiyu Liu, Heyun Shen
An electrophoretic technique was combined with an enzyme-linked immunosorbent assay (ELISA) system to achieve a rapid and sensitive immunoassay. A cellulose acetate filter modified with polyelectrolyte multilayer (PEM) was used as a solid substrate for three-dimensional antigen-antibody reactions. A dual electrophoresis process was used to induce directional migration and local condensation of antigens and antibodies at the solid substrate, avoiding the long diffusion times associated with antigen-antibody reactions in conventional ELISAs...
February 15, 2017: Scientific Reports
Mohammad Reza Keshtkaran, Zhi Yang
OBJECTIVE: Spike sorting is a fundamental preprocessing step for many neuroscience studies which rely on the analysis of spike trains. Most of the feature extraction and dimensionality reduction techniques that have been used for spike sorting give a projection subspace which is not necessarily the most discriminative one. Therefore, the clusters which appear inherently separable in some discriminative subspace may overlap if projected using conventional feature extraction approaches leading to a poor sorting accuracy especially when the noise level is high...
February 15, 2017: Journal of Neural Engineering
Yuchou Chang, Haifeng Wang, Yuanjie Zheng, Hong Lin
Generalized autocalibrating partially parallel acquisition (GRAPPA) has been a widely used parallel MRI technique. However, noise deteriorates the reconstructed image when reduction factor increases or even at low reduction factor for some noisy datasets. Noise, initially generated from scanner, propagates noise-related errors during fitting and interpolation procedures of GRAPPA to distort the final reconstructed image quality. The basic idea we proposed to improve GRAPPA is to remove noise from a system identification perspective...
2017: BioMed Research International
K Collste, P Plavén-Sigray, H Fatouros-Bergman, P Victorsson, M Schain, A Forsberg, N Amini, S Aeinehband, S Erhardt, C Halldin, L Flyckt, L Farde, S Cervenka
Several lines of evidence are indicative of a role for immune activation in the pathophysiology of schizophrenia. Nevertheless, studies using positron emission tomography (PET) and radioligands for the translocator protein (TSPO), a marker for glial activation, have yielded inconsistent results. Whereas early studies using a radioligand with low signal-to-noise in small samples showed increases in patients, more recent studies with improved methodology have shown no differences or trend-level decreases. Importantly, all patients investigated thus far have been on antipsychotic medication, and as these compounds may dampen immune cell activity, this factor limits the conclusions that can be drawn...
February 14, 2017: Molecular Psychiatry
Wenjie Liu, Austen Lambert Davis, William F Siems, Du-Lin Yin, Brian H Clowers, Herbert H Hill
Although higher resolving powers are often achieved using ambient pressure drift tube ion mobility mass spectrometry (DT-IMMS) systems, lower duty cycles are often required which directly impacts sensitivity. Moreover, the mechanism of ion gating using Bradbury-Nielsen or Tyndall-Gate configurations routinely results in ion gate depletion effects which discriminate against low mobility ions. This paper reports a new method of ambient pressure ion mobility operation in which inverse ion mobility spectrometry is coupled to a time of flight mass spectrometer to improve sensitivity and minimize the effects of ion gate depletion...
February 6, 2017: Analytical Chemistry
Uten Yarach, Myung-Ho In, Itthi Chatnuntawech, Berkin Bilgic, Frank Godenschweger, Hendrik Mattern, Alessandro Sciarra, Oliver Speck
PURPOSE: To describe a model-based reconstruction strategy for single-shot echo planar imaging (EPI) that intrinsically accounts for k-space nonuniformity, Nyquist ghosting, and geometric distortions during rather than before or after image reconstruction. METHODS: Ramp sampling and inhomogeneous B0 field-induced distortion cause the EPI samples to lie on a non-Cartesian grid, thus requiring the nonuniform fast Fourier transform. Additionally, a 2D Nyquist ghost phase correction without the need for extra navigator acquisition is included in the proposed reconstruction...
February 10, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Yanhong Li, Shanfa Yu, Guizhen Gu, Guoshun Chen, Yuxin Zheng, Jie Jiao, Wenhui Zhou, Hui Wu, Zengrui Zhang, Huanling Zhang, Lihua He, Qiuyue Yang, Xiangrong Xu
Noise-induced hearing loss (NIHL) is the second-most frequent form of sensorineural hearing loss. When exposed to the same noise, some workers develop NIHL while others do not, suggesting that NIHL may be associated with genetic factors. To explore the relationship between single nucleotide polymorphisms (SNPs) in heat shock protein 70 (HSP70) genes (HSPA1A, HSPA1B and HSPA1L) and susceptibility to NIHL in Han Chinese workers exposed to noise, a case-control association study was carried out with 286 hearing loss cases and 286 matched with gender, age, type of work, and exposure time, drawn from a population of 3790 noise-exposed workers...
2017: PloS One
Johannes Burge, Priyank Jaini
Accuracy Maximization Analysis (AMA) is a recently developed Bayesian ideal observer method for task-specific dimensionality reduction. Given a training set of proximal stimuli (e.g. retinal images), a response noise model, and a cost function, AMA returns the filters (i.e. receptive fields) that extract the most useful stimulus features for estimating a user-specified latent variable from those stimuli. Here, we first contribute two technical advances that significantly reduce AMA's compute time: we derive gradients of cost functions for which two popular estimators are appropriate, and we implement a stochastic gradient descent (AMA-SGD) routine for filter learning...
February 2017: PLoS Computational Biology
Dali Sun, Jia Fan, Chang Liu, Yang Liu, Yang Bu, Christopher J Lyon, Ye Hu
Nanoparticles have become a powerful tool for cell imaging and biomolecule, cell and protein interaction studies, but are difficult to rapidly and accurately measure in most assays. Dark-field microscope (DFM) image analysis approaches used to quantify nanoparticles require high-magnification near-field (HN) images that are labor intensive due to a requirement for manual image selection and focal adjustments needed when identifying and capturing new regions of interest. Low-magnification far-field (LF) DFM imagery is technically simpler to perform but cannot be used as an alternate to HN-DFM quantification, since it is highly sensitive to surface artifacts and debris that can easily mask nanoparticle signal...
December 20, 2016: Analytical Chemistry
Fabio Baselice, Giampaolo Ferraioli, Vito Pascazio
BACKGROUND: Within this manuscript a noise filtering technique for magnetic resonance image stack is presented. Magnetic resonance images are usually affected by artifacts and noise due to several reasons. Several denoising approaches have been proposed in literature, with different trade-off between computational complexity, regularization and noise reduction. Most of them is supervised, i.e. requires the set up of several parameters. A completely unsupervised approach could have a positive impact on the community...
February 7, 2017: Biomedical Engineering Online
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