Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99


Any time

2019 ( 10 )

2018 ( 191 )

2017 ( 172 )

2016 ( 200 )

Custom range...

Search Results: 1 - 10 of 6876 matches for " Quantitative susceptibility mapping "
All listed articles are free for downloading (OA Articles)
Page 1 /6876
Display every page Item
Feasibility of a Direct-Conversion Method from Magnetic Susceptibility to Relative Electron Density for Radiation Therapy Treatment Planning  [PDF]
Kengo Ito, Noriyuki Kadoya, Yujiro Nakajima, Masahide Saito, Kiyokazu Sato, Tatsuo Nagasaka, Kazuomi Yamanaka, Suguru Dobashi, Ken Takeda, Haruo Matsushita, Keiichi Jingu
International Journal of Medical Physics,Clinical Engineering and Radiation Oncology (IJMPCERO) , 2017, DOI: 10.4236/ijmpcero.2017.63023
Abstract: Recently, several institutions have been developing magnetic resonance imaging (MRI)-guided radiotherapy treatment systems. In this study, we examine whether it is possible to perform radiation therapy planning (RTP) using a magnetic susceptibility map obtained using MRI. The head of a healthy volunteer was scanned using dual-energy computed tomography (CT) and MRI. A T2-star-weighted 3D gradient echo-based sequence (GRE) with images taken at four different echo times was acquired using the MRI scanner. The CT images were converted to relative electron density (rED) using a predefined ΔCT-rED conversion table. ΔCT was derived using the energy-subtraction method. The rED map was obtained from a single-linear relationship with the ΔCT-rED conversion table, whereas the magnetic susceptibility map was obtained from quantitative susceptibility mapping (QSM) via MRI. Subsequently, to obtain the relationship between the magnetic susceptibility and the rED, the rED map was rigidly aligned to the susceptibility map and resampled at the susceptibility map’s resolution. Finally, the magnetic susceptibility rED conversion table was obtained via voxel-by-voxel mapping between the two maps. No strong relationship between magnetic susceptibility and rED was obtained in the healthy volunteer’s head or in this study. The coefficient correlation between these parameters was 0.0145. Magnetic susceptibility values may be not able to convert to rED using our proposed method in healthy volunteer’s head. In contrast to the magnetic-susceptibility values obtained from the QSM algorithm, which were strongly affected by calcification and iron content, the rED or CT number was not considerably affected by such materials.
The multi-modal Australian ScienceS Imaging and Visualization Environment (MASSIVE) high performance computing infrastructure: applications in neuroscience and neuroinformatics research
Wojtek J. Goscinski,Paul McIntosh,Christopher J. Hall,Darren Thompson,Graham Galloway,Neil E. B. Killeen,Parnesh Raniga,Amanda Ng,Govinda Poudel,David G. Barnes,Toan Nguyen,Paul Bonnington,Gary F. Egan
Frontiers in Neuroinformatics , 2014, DOI: 10.3389/fninf.2014.00030
Abstract: The Multi-modal Australian ScienceS Imaging and Visualization Environment (MASSIVE) is a national imaging and visualization facility established by Monash University, the Australian Synchrotron, the Commonwealth Scientific Industrial Research Organization (CSIRO), and the Victorian Partnership for Advanced Computing (VPAC), with funding from the National Computational Infrastructure and the Victorian Government. The MASSIVE facility provides hardware, software, and expertise to drive research in the biomedical sciences, particularly advanced brain imaging research using synchrotron x-ray and infrared imaging, functional and structural magnetic resonance imaging (MRI), x-ray computer tomography (CT), electron microscopy and optical microscopy. The development of MASSIVE has been based on best practice in system integration methodologies, frameworks, and architectures. The facility has: (i) integrated multiple different neuroimaging analysis software components, (ii) enabled cross-platform and cross-modality integration of neuroinformatics tools, and (iii) brought together neuroimaging databases and analysis workflows. MASSIVE is now operational as a nationally distributed and integrated facility for neuroinfomatics and brain imaging research.
Advances in clinical application of quantitative susceptibility mapping in central nervous system

ZHANG Zhixue
, LIU Jun, ZHOU Shunke, KOU Zhifeng

- , 2015, DOI: 10.11817/j.issn.1672-7347.2015.07.019
Abstract: 敏感加权成像是一种高分辨率、三维梯度回波、完全速度补偿的MR技术,它对磁化率不同的物质敏感, 然而具有定量特点的重建敏感加权成像图,即定量磁敏感图(quantitative susceptibility mapping,QSM),在钙、铁含 量、微出血、静脉内血氧含量的变化监测的应用价值具有革命性意义。本文仅就QSM的原理及其在中枢神经系统中 的最新应用进展进行综述
Research Progress of Quantitative Susceptibility Mapping in MRI

- , 2015, DOI: 10.7507/1001-5515.20150200
Abstract: 磁化率是一种描述物质内在磁介质属性的物理量,反映的是物质磁化强度与外界所施加的磁场之间的关系。磁量图(QSM)是一种可在体内对组织宏观磁化率定量的磁共振图像(MRI)技术。QSM可清楚显示具有顺磁性或者反磁性组织的解剖结构。QSM算法是解决从测量到的组织磁场中通过非常规的单位偶极子反卷积获得磁化率分布这一病态问题的方法。研究者们提出了多种基于多角度扫描和面向临床单角度扫描的QSM算法来解决这个病态问题。本文通过介绍QSM的基本概念、系统分析当前多种QSM算法、简要介绍QSM的研究进展,旨在促进QSM技术发展和临床应用。
Magnetic susceptibility is an intrinsic physical quantity which describes the relationship between material magnetization and applied external magnetic field. Quantitative susceptibility mapping (QSM) is an MRI technology which can quantify the buck magnetic susceptibility of tissue in vivo. It is particularly effective at elucidating anatomy with paramagnetic or diamagnetic components. QSM technology is a method for solving the ill-pose problem of un-conventional de-convolution of the measured tissue magnetic field with the unit magnetic dipole field to obtain the susceptibility source map. Many multi orientation scan based QSM and clinically acceptable single orientation QSM methods have been proposed to solve this ill-posed problem. In this paper, the QSM concept is introduced and the various QSM methods are systematically categorized and discussed. The aim of this paper is to summarize the current research progress of QSM, popularize the knowledge of QSM and promote the improvements and the rational application of QSM in clinical field.
Magnetic Resonance Image Fusion Based on Three Dimensional Band Limited Shearlet Transform

- , 2015, DOI: 10.7507/1001-5515.20150033
Abstract: 越来越多的医疗设备能采集人体不同特征数据并形成三维图像。在临床应用中, 通常需要将多幅含有不同重要信息的源图像融合到一幅图像中以辅助治疗。而传统的图像融合方法主要针对二维图像, 这些方法直接应用于三维数据会导致第三维信息的损失。本文结合近期出现的超小波变换——三维带限剪切波变换和四组传统融合准则, 提出新的三维磁共振图像融合方法。最后通过四组人脑T2*和磁量图(QSM)源数据, 将本文的方法分别与基于二维和三维的小波、双树复数小波的融合方法进行对比。实验显示基于三维变换的融合方法性能普遍优于基于二维变换的方法; 三维方法中, 剪切波克服了传统小波变换缺乏表达方向的缺陷, 能有效地提高传统图像融合算法的性能, 因此, 本文的方法质量指标最高。
More and more medical devices can capture different features of human body and form three dimensional (3D) images. In clinical applications, usually it is required to fuse multiple source images containing different and crucial information into one for the purpose of assisting medical treatment. However, traditional image fusion methods are normally designed for two dimensional (2D) images and will lead to loss of the third dimensional information if directly applied to 3D data. Therefore, a novel 3D magnetic image fusion method was proposed based on the combination of newly invented beyond wavelet transform, called 3D band limited shearlet transformand (BLST), and four groups of traditional fusion rules. The proposed method was then compared with the 2D and 3D wavelet and dual-tree complex wavelet transform fusion methods through 4 groups of human brain T2* and quantitative susceptibility mapping (QSM) images. The experiments indicated that the performance of the method based on 3D transform was generally superior to the existing methods based on 2D transform. Taking advantage of direction representation, shearlet transform could effectively improve the performance of conventional fusion method based on 3D transform. It is well concluded, therefore, that the proposed method is the best among the methods based on 2D and 3D transforms.
Landslide Investigation with Remote Sensing and Sensor Network: From Susceptibility Mapping and Scaled-down Simulation towards in situ Sensor Network Design
Gang Qiao,Ping Lu,Marco Scaioni,Shuying Xu,Xiaohua Tong,Tiantian Feng,Hangbin Wu,Wen Chen,Yixiang Tian,Weian Wang,Rongxing Li
Remote Sensing , 2013, DOI: 10.3390/rs5094319
Abstract: This paper presents an integrated approach to landslide research based on remote sensing and sensor networks. This approach is composed of three important parts: (i) landslide susceptibility mapping using remote-sensing techniques for susceptible determination of landslide spots; (ii) scaled-down landslide simulation experiments for validation of sensor network for landslide monitoring, and (iii) in situ sensor network deployment for intensified landslide monitoring. The study site is the Taziping landslide located in Hongkou Town (Sichuan, China). The landslide features generated by landslides triggered by the 2008 Wenchuan Earthquake were first extracted by means of object-oriented methods from the remote-sensing images before and after the landslides events. On the basis of correlations derived between spatial distribution of landslides and control factors, the landslide susceptibility mapping was carried out using the Artificial Neural Network (ANN) technique. Then the Taziping landslide, located in the above mentioned study area, was taken as an example to design and implement a scaled-down landslide simulation platform in Tongji University (Shanghai, China). The landslide monitoring sensors were carefully investigated and deployed for rainfall induced landslide simulation experiments. Finally, outcomes from the simulation experiments were adopted and employed to design the future in situ sensor network in Taziping landslide site where the sensor deployment is being implemented.
A Bayesian Algorithm for Functional Mapping of Dynamic Complex Traits
Tian Liu,Rongling Wu
Algorithms , 2009, DOI: 10.3390/a2020667
Abstract: Functional mapping of dynamic traits measured in a longitudinal study was originally derived within the maximum likelihood (ML) context and implemented with the EM algorithm. Although ML-based functional mapping possesses many favorable statistical properties in parameter estimation, it may be computationally intractable for analyzing longitudinal data with high dimensions and high measurement errors. In this article, we derive a general functional mapping framework for quantitative trait locus mapping of dynamic traits within the Bayesian paradigm. Markov chain Monte Carlo techniques were implemented for functional mapping to estimate biologically and statistically sensible parameters that model the structures of time-dependent genetic effects and covariance matrix. The Bayesian approach is useful to handle difficulties in constructing confidence intervals as well as the identifiability problem, enhancing the statistical inference of functional mapping. We have undertaken simulation studies to investigate the statistical behavior of Bayesian-based functional mapping and used a real example with F2 mice to validate the utilization and usefulness of the model.
Linkage disequilibrium fine mapping of quantitative trait loci: A simulation study
Jihad M Abdallah, Bruno Goffinet, Christine Cierco-Ayrolles, Miguel Pérez-Enciso
Genetics Selection Evolution , 2003, DOI: 10.1186/1297-9686-35-6-513
Abstract: (To access the full article, please see PDF)
Eletrencefalograma quantitativo e topográfico (mapeamento cerebral): estudo do padr?o normal para uma popula??o adulta
Arquivos de Neuro-Psiquiatria , 1998, DOI: 10.1590/S0004-282X1998000100009
Abstract: we studied the electric brain activity during wakefulness in 20 brazilian people through digital eeg and spectral analysis in order to propose a standardization for brazilian adult population. all this group is healthy with laboratory examinations and mini-mental state (scores higher than 27) evaluation normal. after fourier fast transformation (fft) calculation, we found a histogram display with monomodal distribution, with higher values in alpha band. analyzing the average of these results, different standards from the analogical traditional eeg were found, as the distribution of alpha band and delta activity behavior. the beta 2 and beta 3 behavior showed a diffuse distribution, that is not the usual. by the other hand, other findings are congruent to the analogical eeg as the alpha posterior predominance and the bigger presence of theta activity at the central regions.
Regional Susceptibility to Domoic Acid in Primary Astrocyte Cells Cultured from the Brain Stem and Hippocampus
Santokh S. Gill,Yangxun Hou,Talat Ghane,Olga M. Pulido
Marine Drugs , 2008, DOI: 10.3390/md6010025
Abstract: Domoic acid is a marine biotoxin associated with harmful algal blooms and is the causative agent of amnesic shellfish poisoning in marine animals and humans. It is also an excitatory amino acid analog to glutamate and kainic acid which acts through glutamate receptors eliciting a very rapid and potent neurotoxic response. The hippocampus, among other brain regions, has been identified as a specific target site having high sensitivity to DOM toxicity. Histopathology evidence indicates that in addition to neurons, the astrocytes were also injured. Electron microscopy data reported in this study further supports the light microscopy findings. Furthermore, the effect of DOM was confirmed by culturing primary astrocytes from the hippocampus and the brain stem and subsequently exposing them to domoic acid. The RNA was extracted and used for biomarker analysis. The biomarker analysis was done for the early response genes including c-fos, c-jun, c-myc, Hsp-72; specific marker for the astrocytes- GFAP and the glutamate receptors including GluR 2, NMDAR 1, NMDAR 2A and B. Although, the astrocyte-GFAP and c-fos were not affected, c-jun and GluR 2 were down-regulated. The microarray analysis revealed that the chemokines / cytokines, tyrosine kinases (Trk), and apoptotic genes were altered. The chemokines that were up-regulated included - IL1-a, IL-1B, IL-6, the small inducible cytokine, interferon protein IP-10, CXC chemokine LIX, and IGF binding proteins. The Bax, Bcl-2, Trk A and Trk B were all downregulated. Interestingly, only the hippocampal astrocytes were affected. Our findings suggest that astrocytes may present a possible target for pharmacological interventions for the prevention and treatment of amnesic shellfish poisoning and for other brain pathologies involving excitotoxicity
Page 1 /6876
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.