928 Hits in 10.5 sec

3-D Residual Eddy Current Field Characterisation: Applied to Diffusion Weighted Magnetic Resonance Imaging

Kieran O'Brien, Alessandro Daducci, Nils Kickler, Francois Lazeyras, Rolf Gruetter, Thorsten Feiweier, Gunnar Krueger
2013 IEEE Transactions on Medical Imaging  
The predicted 3-D eddy current field induced by the diffusion-weighting gradients was able to reduce the root mean square error of the residual eddy current field to~1 Hz.  ...  Index Terms-Brain, diffusion, eddy currents, magnetic resonance imaging (MRI), tractography.  ...  ACKNOWLEDGMENT The authors would like to acknowledge the assistance of Dr. C. Granzeria for assistance with interpretation of the tract based analysis.  ... 
doi:10.1109/tmi.2013.2259249 pmid:23674437 fatcat:tj3rbiosnrbd5arwjuc4drcnsi

The effect of local perturbation fields on human DTI: Characterisation, measurement and correction

Siawoosh Mohammadi, Zoltan Nagy, Harald E. Möller, Mark R. Symms, David W. Carmichael, Oliver Josephs, Nikolaus Weiskopf
2012 NeuroImage  
DTI, however, is susceptible to imaging artefacts, which can bias these indices. The most important sources of artefacts in DTI include eddy currents, nonuniformity and mis-calibration of gradients.  ...  LPFs during the diffusion-weighting period describe the local mismatches between the effective and the expected diffusion gradients resulting in a spatially varying error in the diffusion weighting B matrix  ...  Further thanks go out to Jean Daunizeau for invaluable discussions in the early phases of this project. This study and open access to the paper were supported by the Wellcome Trust.  ... 
doi:10.1016/j.neuroimage.2011.12.009 pmid:22197741 pmcid:PMC3314907 fatcat:leddrlc4cnfsfd7a26hor2fkpe

Characterising Solar Wind Fluctuations at Ion-kinetic Scales

L. D. Woodham, R. T. Wicks, D. Verscharen, C. J. Owen, B. L. Alterman, B. A. Maruca, G. G. Howes, J. M. TenBarge
2019 Zenodo  
In this thesis, I use over a decade of magnetic field and ion measurements from the Wind spacecraft to investigate the physical processes ongoing at these scales.  ...  I then use magnetic helicity to characterise the polarisation properties of the fluctuations, identifying three populations at ion-kinetic scales: quasi-parallel propagating Alfvén-ion cyclotron and fast  ...  After amplification and filtering, the signal is used to generate a current proportional to the magnitude of the applied field.  ... 
doi:10.5281/zenodo.6411639 fatcat:4gbjetjgeza45atgnxrupbenkq

A Fast Protocol for Multiparametric Characterisation of Diffusion in the Brain and Brain Tumours

Ricardo Loução, Ana-Maria Oros-Peusquens, Karl-Josef Langen, Hugo Alexandre Ferreira, N. Jon Shah
2021 Frontiers in Oncology  
Multi-parametric tissue characterisation is demonstrated using a 4-minute protocol based on diffusion trace acquisitions.  ...  In conclusion, we introduce a clinically applicable protocol for measuring multiple parameters and demonstrate its relevance to pathological tissue characterisation.  ...  HAF would like to further thank Fundacão para a Ciencia e Tecnologia for financial support under the project UID/BIO/00645/2019 and POCI-01-0145-FEDER-016428.  ... 
doi:10.3389/fonc.2021.554205 pmid:34621664 pmcid:PMC8490752 fatcat:oib7ezw3dnccpoqbl3ctjfjigi

Manufacture, characterisation and application of cellular metals and metal foams

John Banhart
2001 Progress in Materials Science  
Finally, the various application fields for cellular metals are discussed.  ...  The various ways for characterising the properties of cellular metals are reviewed in second section of this paper. Non-destructive as well as destructive methods are described.  ...  Induction causes eddy currents and a corresponding magnetic field around the metal foam sample, which can then be picked up with a secondary coil.  ... 
doi:10.1016/s0079-6425(00)00002-5 fatcat:6ore6scui5gcpcr3256lf4bwxy

Characterisation of the long-term effects of anthracycline-associated myocardial toxicity using cardiac MRI; a pilot study

Marina L Hughes, Frederique Bailliard, Andrew Taylor, Gill Levitt
2009 Journal of Cardiovascular Magnetic Resonance  
resonance study  ...  The cardiomyopathy is reversible if chelation is commenced early but diagnosis is often delayed due to the late onset of symptoms.  ...  Further studies with patients are required to assess sensitivity and specificity.  ... 
doi:10.1186/1532-429x-11-s1-p95 fatcat:wcv5tzckuncspkbd6vk33gdowy

Realistic simulation of artefacts in diffusion MRI for validating post-processing correction techniques

Mark S. Graham, Ivana Drobnjak, Hui Zhang
2016 NeuroImage  
In this paper we demonstrate a simulation framework that enables the direct and quantitative comparison of post-processing methods for diffusion weighted magnetic resonance (DW-MR) images.  ...  Artefacts such as eddy-current (EC) distortion and motion lead to misalignment between images, which compromise the quality of the microstructural measures obtained from them.  ...  Acknowledgments We would like to thank Jesper Andersson for providing us with a version of eddy that outputs displacement fields, and for helpful discussions.  ... 
doi:10.1016/j.neuroimage.2015.11.006 pmid:26549300 fatcat:iuyrfh5mbzg6rgavqin3rhcvsy

Short echo time single voxel 1H magnetic resonance spectroscopy in the diagnosis and characterisation of pineal tumours in children

Lisa M. Harris, Nigel P. Davies, Shaun Wilson, Lesley MacPherson, Kal Natarajan, Martin W. English, Marie-Anne Brundler, Theodoros N. Arvanitis, Richard G. Grundy, Andrew C. Peet
2011 Pediatric Blood & Cancer  
INTRODUCTION Brain tumours are the most common solid tumour in childhood, while Magnetic Resonance Spectroscopy (MRS) studies have been performed on brain tumours previously, the majority have been performed  ...  METHODS Short echo time MRS was performed on children with brain tumours at the time of diagnostic imaging. In addition, follow up data was accrued for some patients.  ...  ACKNOWLEDGEMENTS There are a large number of people I would like to thank, and without whom this thesis is unlikely to have been written.  ... 
doi:10.1002/pbc.23044 pmid:21793176 fatcat:56jfngc4snfchetz2ml5uzq2ou

Susceptibility-induced distortion that varies due to motion: Correction in diffusion MR without acquiring additional data

Jesper L.R. Andersson, Mark S. Graham, Ivana Drobnjak, Hui Zhang, Jon Campbell
2018 NeuroImage  
A B S T R A C T Because of their low bandwidth in the phase-encode (PE) direction, the susceptibility-induced off-resonance field causes distortions in echo planar imaging (EPI) images.  ...  Hence, if using a single field to correct for distortions there will be residual distortions in the volumes where the object orientation is substantially different to that when the field was measured.  ...  Acknowledgments We would like to thank Steve Smith, Mark Jenkinson and Stuart Clare for support and helpful discussions and Chloe Hutton for help with the English language.  ... 
doi:10.1016/j.neuroimage.2017.12.040 pmid:29277648 pmcid:PMC5883370 fatcat:sf2x53ogprfjvov3a4tvcnwwga

Towards an optimised processing pipeline for diffusion magnetic resonance imaging data: Effects of artefact corrections on diffusion metrics and their age associations in UK Biobank

Ivan I. Maximov, Dag Alnæs, Lars T. Westlye
2019 Human Brain Mapping  
Diffusion weighted magnetic resonance imaging data enables a range of promising imaging phenotypes probing structural connections as well as macroanatomical and microstructural properties of the brain.  ...  Using diffusion magnetic resonance imaging (MRI) data from 218 individuals in the UK Biobank, we evaluate the effects of different processing steps that have been suggested to reduce imaging artefacts  ...  To avoid bias based on the field nonuniformity, we applied a bias field correction for b = 0 s/mm 2 image.  ... 
doi:10.1002/hbm.24691 pmid:31173439 fatcat:dnxsuabtjvew5enuw3g42lai64

An improved equivalent magnetization current method applied to the design of local breast gradient coils

Hector Sanchez Lopez, Michael Poole, Stuart Crozier
2009 Journal of magnetic resonance (San Diego, Calif. 1997 : Print)  
Magnetic resonance imaging (MRI) is an important tool in the diagnosis of breast cancer.  ...  Strong gradients also facilitate diffusion studies; one well-known method of increasing gradient strength is to design local gradient coils, those with reduced diameter where the gradient conductors are  ...  such as diffusion-weighted imaging of the breast [7] .  ... 
doi:10.1016/j.jmr.2009.03.011 pmid:19375368 fatcat:ubr6wppys5afdhjn7h7saikfbm

Strong diffusion gradients allow the separation of intra- and extra-axonal gradient-echo signals in the human brain

Elena Kleban, Chantal M.W. Tax, Umesh S. Rudrapatna, Derek K. Jones, Richard Bowtell
2020 NeuroImage  
The quantification of brain white matter properties is a key area of application of Magnetic Resonance Imaging (MRI), with much effort focused on using MR techniques to quantify tissue microstructure.  ...  tissue microstructure by observing the effect of interaction between the tissue and the magnetic field.  ...  induced by eddy-current-related field perturbations.  ... 
doi:10.1016/j.neuroimage.2020.116793 pmid:32335263 pmcid:PMC7613126 fatcat:ftgtdir6o5e3jctophwspb3oje

Incorporating outlier detection and replacement into a non-parametric framework for movement and distortion correction of diffusion MR images

Jesper L. R Andersson, Mark S. Graham, Enikő Zsoldos, Stamatios N. Sotiropoulos
2016 NeuroImage  
Artefacts in diffusion imaging include • Image distortions due to field inhomogeneities caused by the subject's head (susceptibility). • Image distortions due to eddy currents caused by rapid gradient  ...  the main magnetic field, the susceptibilityinduced off-resonance field changes ).  ... 
doi:10.1016/j.neuroimage.2016.06.058 pmid:27393418 fatcat:lvx4tr4t6rgxdofg3gelcoblqq

Diffusion-Exchange Weighted Imaging

Saadallah Ramadan
2009 Magnetic Resonance Insights  
A method has been developed whereby diffusion and exchange in micro cellular structures in the human brain are correlated to produce a new type of image contrast leading to determination of water exchange  ...  The method was tested in vivo at 3T field strength and produced 160 ms and 550 ms for extra-cellular and intra-cellular mean residence times, respectively.  ...  High-amplitude diffusion gradients may produce eddy currents even in a system with reasonable eddy-current compensation.  ... 
doi:10.4137/mri.s3504 fatcat:d7uxyns57jhzlfdbdy3jgynl2m

In vivo High Angular Resolution Diffusion-Weighted Imaging of Mouse Brain at 16.4 Tesla

Othman I. Alomair, Ian M. Brereton, Maree T. Smith, Graham J. Galloway, Nyoman D. Kurniawan, Ichio Aoki
2015 PLoS ONE  
Magnetic Resonance Imaging (MRI) of the rodent brain at ultra-high magnetic fields (> 9.4 Tesla) offers a higher signal-to-noise ratio that can be exploited to reduce image acquisition time or provide  ...  The Stejskal-Tanner spin echo diffusion-weighted imaging (DWI) sequence is often used in high-field rodent brain MRI due to its immunity to these artefacts.  ...  The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.  ... 
doi:10.1371/journal.pone.0130133 pmid:26110770 pmcid:PMC4482319 fatcat:heubypfqfbe65fzxq5twh63odi
« Previous Showing results 1 — 15 out of 928 results