Motion artifact reduction in photoplethysmography using independent component analysis

Removing the motion artifacts from measured photoplethysmography (PPG) signals is one of the important issues to be tackled for the accurate measurement of arterial oxygen saturation during movement. In this paper, the motion artifacts were reduced by exploiting the quasi-periodicity of the PPG signal and the independence between the PPG and the motion artifact signals. The combination of independent component analysis and block interleaving with low-pass filtering can reduce the motion artifacts under the condition of general dual-wavelength measurement. Experiments with synthetic and real data were performed to demonstrate the efficacy of the proposed algorithm.     

利用轨迹修复改进CT金属伪影去除算法的研究

金属伪影严重地影响CT图像的质量及其医学诊断价值。考虑到临床数据的可靠性及时效性,正弦图修复及其改进的方法已成为近年来研究的热点。典型的NMAR方法(Normalized Metal Artifact Reduction),多数情况下能准确地恢复原始数据,并尽可能少地残留或引入新的伪影。然而当出现高密度组织（骨头等）与金属不相邻时,就会在金属与高密度组织间不可避免地引入或残留部分伪影。本文在NMAR算法的基础上,引入了一种基于正弦图中轨迹修复的金属伪影去除方法(TNMAR）。具体地,在NMAR方法中正弦图归一化后的区域修复期间,引入了高密度组织轨迹方向的平滑修复。此方法一定程度上削减了NMAR修复后金属与高密度组织间的残留伪影,且尽可能地恢复了原图的高对比度及组织细节。临床中,有很高的应用价值。      

Blind compression artifact reduction using dense parallel convolutional neural network

Different artifacts will manifest, whenever an image is compressed by a lossy compression algorithm. Higher frequency details present in the image may tend to be eliminated by compression. In certain cases, compression may introduce small image structures and noise. This phenomenon will limit the image quality thereby making images to appear much less pleasant to the human eye. Furthermore, other machine learning tasks like object detectors performance will be reduced due to compression. In this paper, we introduce a novel deep neural network with densely connected parallel convolutions to remove such artifacts and to recover the original image from its perturbed version. The proposed algorithm is named as densely connected parallel convolutional neural network in short DPCNN. Parallel convolution provides model parallelism and reduce the training burden. Furthermore, the dense skip connections provide short paths for gradient back-propagation and alleviates the gradient vanishing problem. Moreover, skip connections reduce the feature redundancy by combining features from different levels and increases the learning efficiency. However, these skip connections increase the model complexity. A bottleneck layer is used to keep the model compactness and to reduce the model complexity. The proposed approach can be used as a preprocessing step in different computer vision tasks where images are degraded by compression. Different from other methods, the proposed method is able to remove compression artifacts generated at any quality factor (QF). The experiments on benchmark datasets show the superiority of the proposed method over other methods quantitatively and qualitatively.     

Antenna size reduction using non-planar rings

There is a constant need to reduce the size of antennas without affecting their performance. The method of shorting patches to reduce the physical size of antennas is a common practice. The use of finite ground planes with these types of antennas can have a negative effect on their performance. Here, the introduction of non-planar rings in conjunction with a shorted patch to minimise the negative effects of the finite ground plane resulting in an overall antenna size reduction and an improvement in antenna performance is proposed     

Data truncation artifact reduction in MR imaging using a multilayer neural network

A magnetic resonance image (MRI) may contain truncation artifacts if there are not enough high-frequency data when the conventional Fourier transform method is used for reconstruction. A method for reducing the artifacts using a multilayer neural network is presented. The network consists of one linear output layer and at least one nonlinear hidden layer. The missing high-frequency components are predicted based on known low-frequency components and are used to reduce the truncation artifacts of the image. Results from a series of simulation experiments are discussed.     

Regression-based prediction for blocking artifact reduction in JPEG-compressed images.

In order to reduce the blocking artifact in the Joint Photographic Experts Group (JPEG)-compressed images, a new noniterative postprocessing algorithm is proposed. The algorithm consists of a two-step operation: low-pass filtering and then predicting. Predicting the original image from the low-pass filtered image is performed by using the predictors, which are constructed based on a broken line regression model. The constructed predictor is a generalized version of the projector onto the quantization constraint set, or the narrow quantization constraint set. We employed different predictors depending on the frequency components in the discrete cosine transform (DCT) domain since each component has different statistical properties. Further, by using a simple classifier, we adaptively applied the predictors depending on the local variance of the DCT block. This adaptation enables an appropriate blurring depending on the smooth or detail region, and shows improved performance in terms of the average distortion and the perceptual view. For the major-edge DCT blocks, which usually suffer from the ringing artifact, the quality of fit to the regression model is usually not good. By making a modification of the regression model for such DCT blocks, we can also obtain a good perceptual view. The proposed algorithm does not employ any sophisticated edge-oriented classifiers and nonlinear filters. Compared to the previously proposed algorithms, the proposed algorithm provides comparable or better results with less computational complexity.     

Antenna size reduction using Yagi-Uda loops and shorted circular patches

The reduction in the size of antennas for personal communication systems applications is a research area that is receiving lots of attention. The literature concentrates on reducing the size of microstrip patches however most of these antenna types require a large ground plane. Reducing the size of the ground plane has adverse affects on the antenna. To counter these affects a novel antenna type is presented. This antenna uses a shorted circular patch surrounded with nonplanar rings. These rings allow a reduction in the ground plane to a radius of less than 0.23 /spl lambda/ and improve its radiation characteristics. Through examination of the currents on the antenna, the principle of operation is explained based on a Yagi-Uda like array concept. Further theoretical and experimental examination confirms the above explanation.     

X-ray CT metal artifact reduction using wavelets: an application for imaging total hip prostheses

Traditional computed tomography (CT) reconstructions of total joint prostheses are limited by metal artifacts from corrupted projection data. Published metal artifact reduction methods are based on the assumption that severe attenuation of X-rays by prostheses renders corresponding portions of projection data unavailable, hence the "missing" data are either avoided (in iterative reconstruction) or interpolated (in filtered backprojection with data completion; typically, with filling data "gaps" via linear functions). In this paper, we propose a wavelet-based multiresolution analysis method for metal artifact reduction, in which information is extracted from corrupted projection data. The wavelet method improves image quality by a successive interpolation in the wavelet domain. Theoretical analysis and experimental results demonstrate that the metal artifacts due to both photon starving and beam hardening can be effectively suppressed using our method. As compared to the filtered backprojection after linear interpolation, the wavelet-based reconstruction is significantly more accurate for depiction of anatomical structures, especially in the immediate neighborhood of the prostheses. This superior imaging precision is highly advantageous in geometric modeling for fitting hip prostheses.     

Comments on "Data truncation artifact reduction in MR imaging using a multilayer neural network"

A recent paper by Yan and Mao (see ibid., vol.12, no.1, p.73-7, 1993) provided the results of using a neural network based nonlinear prediction algorithm to extrapolate truncated magnetic resonance data. The extrapolation is intended to reduce the truncation artifacts that result when reconstructing an image from a limited k-space magnetic resonance data set using the discrete Fourier transform. When attempting to quantitatively compare Yan and Mao's method with the authors' own existing constrained modeling algorithm, the authors discovered a systematic error in Yan and Mao's analysis. With the error corrected, it was found that Yan and Mao's approach worked significantly better than they have reported and was more stable in the presence of noise.     

基于PCA和自适应步长IVA的EMG伪迹去除方法

针对脑电(EEG)信号在采集过程中易受到肌电(EMG)伪迹干扰,且EMG伪迹复杂多变难以去除的问题,提出一种基于主分量分析(PCA)和自适应步长独立向量分析(IVA)相结合的EEG中EMG伪迹去除方法。首先,利用PCA将EEG信号的主分量提取出来,对数据降维;然后对主分量引入IVA算法,根据高阶统计量和二阶统计量,结合EMG伪迹的非高斯性和弱相关性进行EMG伪迹分离,同时引入基于分离效果的自适应步长选取方法,增强分离效果。实验中采集了8通道的EEG信号,测得各通道相对均方根误差为0.09～0.2,算法的平均EMG伪迹分离率为98%,且相比单独使用IVA时间节省20%,该方法适用于动态EEG中EMG伪迹的去除。     

High-frequency electrical stimulation of cardiac cells and application to artifact reduction

A novel modality for the electrical stimulation of cardiac cells is described. The technique is based on HF stimulation-burst of HF (1-25 kHz) biphasic square waves-to depolarize the cells and trigger action potentials (APs). HF stimulation was demonstrated in HL-1 cardiomyocyte cultures using microelectrode arrays, and the underlying mechanisms were investigated using single-cell model simulations. Current thresholds for HF stimulation increased at higher frequencies or shorter burst durations, and were typically higher than thresholds for single biphasic pulses. Nonetheless, owing to the decreasing impedance of metal electrodes with increasing frequencies, HF bursts resulted in reduced electrode voltages (up to four fold). Such lowered potentials might be beneficial in reducing the probability of irreversible electrochemical reactions and tissue damage, especially for long-term stimulation. More significantly, stimulation at frequencies higher than the upper limit of the AP power spectrum allows effective artifact reduction by low-pass filtering. Shaping of the burst envelope provides further reduction of the remaining artifact. This ability to decouple extracellular stimulation and recording in the frequency domain allowed detection of APs during stimulation-something previously not achievable to the best of our knowledge.     

A design of the low-pass filter using the novel microstrip defectedground structure

A new defected ground structure (DGS) for the microstrip line is proposed in this paper. The proposed DGS unit structure can provide the bandgap characteristic in some frequency bands with only one or more unit lattices. The equivalent circuit for the proposed defected ground unit structure is derived by means of three-dimensional field analysis methods. The equivalent-circuit parameters are extracted by using a simple circuit analysis method. By employing the extracted parameters and circuit analysis theory, the bandgap effect for the provided defected ground unit structure can be explained. By using the derived and extracted equivalent circuit and parameters, the low-pass filters are designed and implemented. The experimental results show excellent agreement with theoretical results and the validity of the modeling method for the proposed defected ground unit structure     

High-selectivity grounded capacitor bandpass/low-pass filters using the operational amplifier pole

Using the single-pole model of the operational amplifier (OA) a grounded capacitor network has been analyzed to yield either a bandpass or a low-pass function by adjustment of a single resistor. The bandpass/low-pass filters are suitable for high selectivity applications at extended frequency ranges with the advantage of independent adjustment of pole-frequency, pole-Q factor, and midband/passband transmission gain. The network has low sensitivity to all the circuit parameters. The experimental results are quite in agreement with the analysis.     

A respiratory motion artifact reduction method in magnetic resonance imaging of the chest

An image reconstruction algorithm based on the assumption that the respiratory motion of the chest is linear in space and arbitrary in time is presented. The linear respiratory motion causes phase distortion on the magnetic resonance (MR) data. As a result of this motion, the MR data are the samples of the Fourier transform of the spin density on a nonrectangular grid. In image reconstruction. before taking the inverse Fourier transform, the phase distortion is compensated for, and the rectangular samples are interpolated from the existing nonrectangular samples. A significant amount of motion artifact suppression is achieved with a rough knowledge on the motion using this method. It is demonstrated that the respiratory motion model parameters can be estimated using the information hidden in the motion artifacts.     

Stopband-enhanced and size-miniaturized low-pass filters using high-impedance property of offset finite-ground microstrip line

The uniform finite-ground microstrip line (FGMSL) and its constituted circuit elements are thoroughly characterized via self-calibrated method of moments for innovative design of a stopband-enhanced and size-miniaturized low-pass filter (LPF). Firstly, an offset FGMSL is modeled and extracted to quantitatively exhibit its capacity in achieving higher characteristic impedance compared to the infinite-ground microstrip line (MSL) counterpart. Secondly, the finite-extended FGMSL section with equally widened strip/ground or offset narrow strip/ground conductors is studied in terms of an equivalent T- or /spl pi/-network, thereby constructing the modified MSL shunt capacitive or series inductive element. By making effective use of enlarged series inductance of an offset FGMSL with shorter electrical length, two novel LPF blocks are designed on a basis of cascaded circuit networks. Predicted S-parameters show widened and deepened stopband beyond the low passband. Furthermore, it is confirmed by measurement.     

New grounded-capacitor realizations of a third-order low-pass butterworth characteristic using the DVCCS/DVCVS

Two new configurations employing the differential voltage-controlled current/voltage source (DVCCS/DVCVS) are proposed for the realization of either an inverting or a noninverting third-order low-pass Butterworth transfer function. Both structures use a minimum of passive components which are of equal value with the capacitors being grounded. The sensitivities of the network parameters are low.     

ITRS 2001与芯片特征尺寸的缩小

2001《国际半导体技术指南(ITRS)》规划出半导体技术未来15年内的发展。它主要强调芯片特征尺寸的进一步缩小,2001年0.13μm,2004年90nm,2007年70nm,2010年50nm,2013年30nm,2016年22nm。阻碍芯片特征尺寸缩小的关键是光学光刻技术,为此,世界各强国加速开发下一代光学光刻技术,如157nm光学光刻、电子束光刻(EBL)和极紫外线(EUVL)光刻等。展望了缩小芯片特征尺寸的前景和存在的问题。     

Efficient transform-domain size and resolution reduction of images

This paper describes techniques for adapting a transform-based image (such as JPEG) so that it conforms to specific compressed size or dimension criteria. For compressed size adaptation, the proposed method operates efficiently in the transform domain, but yields visually improved results when compared to existing approaches. For resolution adaptation, the proposed method results in a speed improvement of 76% over the baseline algorithm and 31% over other previous work, with minimal or no difference in overall visual quality.     

Compact planar and vialess composite low-pass filters using folded stepped-impedance resonator on liquid-Crystal-polymer substrate

A compact composite low-pass filter, designed by the image parameter method and semilumped component approach, will be described and results for cutoff frequency ranging from C- to V-band will be presented. This composite design combines four filter sections and the presence of a strong attenuation pole near the cutoff frequency provides an extremely sharp attenuation response, while ensuring good matching properties in the passband, making this filter design very attractive for harmonic spurious response suppression or diplexing. The lumped-element schematic of the filter has been implemented using a combination of a stepped-impedance filter and folded stepped-impedance resonators. The overall folded layout has been optimized using full-wave simulation and occupies an ultra-compact area of only 5/spl times/5 mm/sup 2/ for a C-band filter. Measured results exhibit rejection of the attenuated pole greater than 40 dB. Similar filter designs have been realized for C- and V-bands. These filters have been fabricated on a liquid-crystal-polymer substrate demonstrating a high performance, ultra-compact, and very low-cost solution for RF and millimeter-wave applications.