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A RVR-based Method for bias field Estimation in Brain Magnetic Resonance Images Segmentation

Chinese Journal of Biomedical Engineering(English Edition) 2015年第2期24卷 73-79页

作者： WANG Jin-wei KONG De-xing Center of Mathematical Sciences Zhejiang University Department of Mathematics Zhejiang University

This paper presents a relevance vector regression(RVR) based on parametric approach to the bias field estimation in brain magnetic resonance(MR) image segmentation. Segmentation is a very important and challenging task in brain analysis,while the bias field existed in the images can significantly deteriorate the performance.Most of current parametric bias field correction techniques use a pre-set linear combination of low degree basis functions, the coefficients and the basis function types of which completely determine the field. The proposed RVR method can automatically determine the best combination for the bias field, resulting in a good segmentation in the presence of noise by combining with spatial constrained fuzzy C-means(SCFCM)segmentation. Experiments on simulated T1 images show the efficiency.

关键词： bias field segmentation relevance vector regression(RVR) spatial constrained fuzzy C-means(SCFCM) estimation

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A Modified Fuzzy C-Means for bias field Estimation and Segmentation of Brain MR Image 25th

A Modified Fuzzy C-Means for Bias Field Estimation and Segme...

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第25届中国控制与决策会议

作者： Zhang Shi She Lihuang Lu Li Zhong Hua Northeastern University

ISBN: (纸本)9781467355339

Fuzzy C-means clustering （FCM） algorithm is good at solving the ambiguities and uncertainties in the image, and the modified FCM has been widely used in solving the intensity inhomogeneity problem. bias-corrected FCM （BCFCM） is very useful for noise and intensity inhomogeneity image segmentation, but it can’t estimate accurately the pixels on the boundary especially in the regions with heavy level of intensity inhomogeneous. In this paper, we present a novel algorithm for brain magnetic resonance imaging （MRI） Image segmentation and intensity inhomogeneity estimation based on BCFCM. The proposed algorithm introduces the global intensity information into the algorithm BCFCM, for the smooth bias field estimation and more accurate segmentations. The proposed method has been successfully applied to MR brain images, and experiment results show that this method is superior to FCM, BCFCM and some other approaches.

关键词： bias field Fuzzy C-means clustering mage segmentation Global information MR imaging

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Brain MR Image Segmentation and bias field Estimation Using Coherent Local and Non-local Spatial Constraints

Brain MR Image Segmentation and Bias Field Estimation Using ...

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第25届中国控制与决策会议

作者： Zhang Shi She Lihuang Wang Hongyan Zhong Hua Academy of Information Science and Engineering Northeastern University

ISBN: (纸本)9781467355339

Clinical brain MR images usually contain noise and bias field （BF）, which make the brain tissue segmentations difficult. Most of the current segmentation methods only focus on one unfavorable factor. The Coherent local intensity clustering algorithm （CLIC） algorithm proposed recently is good at dealing with the BF problem in images, but it has a poor anti-noise ability, for it doesn’t consider non-local spatial constraint. In this paper, taking care of all these unfavorable factors simultaneously, we introduce the non-local spatial constraint into CLIC algorithm for brain MR image segmentations. Therefore, the proposed algorithm drives by both the coherent local and non-local spatial constraints. The coherent local information ensures the smoothness of the bias field estimation and the non-local spatial information reduces the noise effect during the segmentation. The proposed method has been successfully applied to brain MR images, and experiment results show that this method has stronger anti-noise property, smoother bias field estimation and higher segmentation precision than other reported fuzzy clustering algorithms.

关键词： bias field fuzzy clustering MR image segmentation non-local constraint coherent local constraint

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THEORY ON THE LASER EXCITED WAVE PROPAGATION IN A SINGLE PIEZOELECTRIC PLATE UNDER A bias ELECTRIC field

THEORY ON THE LASER EXCITED WAVE PROPAGATION IN A SINGLE PIE...

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2012全国压电和声波理论及器件技术研讨会

作者： Gen CHEN Yong-dong PAN Zheng ZHONG Institute of Acoustics Tongji University School of Aerospace Engineering and Applied Mechanics Tongji University

The laser excited wave propagation in a single piezoelectric plate under a bias electric field is studied theoretically.The state vector approach is used to derive the differential equations for the piezoelectric plate under a bias electric field.The laser is modeled as a transient force at the boundary.By solving the state space equation,both the dispersion curves and surface displacement of the epicenter of the single piezoelectric plate under the laser ablation excitation with bias electric field are obtained.It is found that the wave propagation in the piezoelectric is influenced by the bias electric field.The numerical calculation shows that along the polarization direction,the velocity of the acoustic wave in the piezoelectric plate with positive bias electric field is larger than that without any electric field,which is just an inversed situation in the negative configuration.The theoretical findings will provide the basis for the further experimental investigation.

关键词： Piezoelectric plate Laser ultrasonics bias field Active control

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field-dependent spin waves in high-aspect-ratio singlecrystal ferromagnetic nanowires

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Nano Research 2016年第5期9卷 1426-1433页

作者： Semanti Pal Susmita Saha M. Venkata Kamalakar Anjan Barman Department of Condensed Matter Physics and Material Sciences S. N. Bose National Centre for Basic Sciences Block JD Sector Ⅲ Salt Lake Kolkata 700 098 India Department of Physics and Astronomy Uppsala University Box 516 75120 Uppsala Sweden

We investigate the spin wave （SW） modes in high-aspect-ratio single-crystal ferromagnetic nanowires （FMNWs） using an all-optical time-resolved magnetooptical Kerr effect （TR-MOKE） microscope. The precessional magnetization dynamics in such FMNWs unveil the presence of uniform and quantized SW modes that can be tuned by varying the bias magnetic field （H）. The frequencies of the modes are observed to decrease systematically with a decreasing magnetic field, and the number of modes in the spectrum is reduced from four to three for H 〈 0.7 kOe. To understand these results, we perform micromagnetic simulations that reveal the presence of edge, standing wave, and uniform SW modes in the nanowires （NWs）. Our simulations clearly show how the standing wave and uniform SW modes coalesce to form a single mode with uniform precession over the entire NW for H 〈 0.7 kOe, reproducing the experimentally observed reduction in modes. Our study elucidates the possibility of manipulating the SW modes in magnetic nanostructures, which is useful for applications in magnonic and spintronic devices.

关键词： Spin Wave bias field Ferromagnetic Resonance Magnetization Dynamic Uniform Mode

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Influence of Temperature on Equilibrium Separation Between Vertical Bloch Lines in OHBs in Garnet Bubble Films

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Chinese Physics Letters 2009年第1期26卷 314-316页

作者：孙会元胡云志刘力虎 Hebei Advanced Thin Films Laboratory College of Physics Hebei Normal University Shijiazhuang 050016 Higher Education Publishing Center Science Press Limited Company Beijing 100717

The diameters of the ordinary hard bubbles （OHBs） and soft bubbles in epitaxial garnet films are measured under the microscope at various temperatures. It is found that the bubble diameters of OHBs increase with temperature, and it is concluded that the equilibrium separation between two neighbouring vertical Bloch lines （VBLs） Seq is widened with increasing temperature. At the same time, the results can be understood simply as that there are more VBLs in the domain walls of the first dumbbell domains （IDs） than those in walls of OHBs at the same temperature.

关键词： HARD DOMAINS DUMBBELL DOMAINS bias field 3 KINDS WALLS STATE

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