Filters








5,487 Hits in 10.5 sec

Texture Analysis in Magnetic Resonance Imaging: Review and Considerations for Future Applications [chapter]

Andrés Larroza, Vicente Bodí, David Moratal
2016 Assessment of Cellular and Organ Function and Dysfunction using Direct and Derived MRI Methodologies  
It has been successfully used in many fields, and in the past years it has been applied in magnetic resonance imaging (MRI) as a computer-aided diagnostic tool.  ...  Texture analysis is a technique used for the quantification of image texture.  ...  [51] comparing three interpolation methods applied on T2-weighted images acquired at five different resolutions.  ... 
doi:10.5772/64641 fatcat:sw7nodso7rfpfjohaopmrt2zta

Functional MRI of the Human Amygdala?

Klaus-Dietmar Merboldt, Peter Fransson, Harald Bruhn, Jens Frahm
2001 NeuroImage  
image quality of T2*-weighted echoplanar imaging (EPI) and fast low angle shot (FLASH) sequences at 2.0-T with regard to susceptibility-induced signal losses and geometric distortions.  ...  Apart from the timing of the gradient echoes, the degree of susceptibility influences is controlled by the image voxel size.  ...  FIG. 1 . 1 Susceptibility artifacts in T2*-weighted gradient-echo MRI of a transverse section through both amygdalas centrally (see arrows).  ... 
doi:10.1006/nimg.2001.0802 pmid:11467900 fatcat:cxjpdkisfza43otpfjka7hfzye

Direct in vitro comparison of six three-dimensional positive contrast methods for susceptibility marker imaging

Evert-jan P.A. Vonken, Michael Schär, Jing Yu, Chris J.G. Bakker, Matthias Stuber
2012 Journal of Magnetic Resonance Imaging  
Purpose-To compare different techniques for positive contrast imaging of susceptibility markers with MRI for 3D visualization.  ...  Materials and methods- Six different positive contrast techniques are investigated for their ability to image at 3T a single susceptibility marker in vitro.  ...  Acknowledgments We would like to thank J-H Seppenwoolde for providing us with the susceptibility marker used to build the phantom.  ... 
doi:10.1002/jmri.23976 pmid:23281151 pmcid:PMC3620818 fatcat:k44t6xq2fbbgvkxmazojtqpfxa

Imaging of short and ultrashort T2and T2* tissues using clinical MRI systems

Graeme M Bydder
2010 Imaging in Medicine  
Specific methods have been developed to image the effects of magnetic iron oxide particles with positive contrast and to correct for the loss of signal and image distortion near to metal caused by gross  ...  Particular methods have been developed to target susceptibility effects, and allow accurate quantitation by compensating for the anatomical distortion produced by these effects.  ...  susceptibility-weighted imaging Susceptibility-weighted imaging has been in use for a considerable time.  ... 
doi:10.2217/iim.10.8 fatcat:6xokq4oc2vfnhahlm5zuaju57y

Positive contrast visualization of nitinol devices using susceptibility gradient mapping

Evert-jan P.A. Vonken, Michael Schär, Matthias Stuber
2008 Magnetic Resonance in Medicine  
This method operates on regular gradient echo MR images and maps the shift in k-space in a (small) neighborhood of every voxel by Fourier analysis followed by a center of mass calculation.  ...  The properties of the method are explained and the visualization of a nitinol wire and two stents are shown for illustration.  ...  Acknowledgments We would like to thank our colleagues Di Qian, for making the nitinol wires available to us, and John Terrovitis for suspending them in agarose to create the phantom.  ... 
doi:10.1002/mrm.21688 pmid:18727096 pmcid:PMC2627583 fatcat:mtprsodwsfb55odrtuhpjp2rvm

A Review of MR Physics: 3T versus 1.5T

Brian J. Soher, Brian M. Dale, Elmar M. Merkle
2007 Magnetic Resonance Imaging Clinics of North America  
Image artifacts because of changes in tissue susceptibility, chemical shift, RF effects, and/or pulse sequence physics are more noticeable and sometimes harder to suppress at high field.  ...  -Susceptibility -Contrast agents -Specific artifacts Chemical shift artifacts of the first and second kinds B 1 inhomogeneity and standing wave artifacts Steady-state pulse sequence banding artifacts -  ...  ffi N PE N PA N AV BW r sinðqÞ À 1 À e ÀTR=T1 Á ð1 À e ÀTR=T1 cosðqÞÞ e ÀTE=T2 Ã ð3Þ (Equation 3 for gradient-echo-based MR sequences), where, SNR SE 5 signal-to-noise ratio for a spin echo pulse sequence  ... 
doi:10.1016/j.mric.2007.06.002 pmid:17893049 fatcat:mafgbgrrczaofdjgivlytfx344

Magnetic susceptibility-induced echo-time shifts: Is there a bias in age-related fMRI studies?

Giang-Chau Ngo, Chelsea N. Wong, Steve Guo, Thomas Paine, Arthur F. Kramer, Bradley P. Sutton
2016 Journal of Magnetic Resonance Imaging  
Conclusion-Susceptibility-induced magnetic field gradients induce local echo time shifts in gradient echo fMRI images, which can cause variable BOLD sensitivity across the brain.  ...  Purpose-To evaluate the potential for bias in functional MRI (fMRI) aging studies resulting from age-related differences in magnetic field distributions which can impact echo time and functional contrast  ...  The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute Of Biomedical Imaging And Bioengineering or the National Institutes  ... 
doi:10.1002/jmri.25347 pmid:27299727 pmcid:PMC5156585 fatcat:gqtiqxujvvckthrbh64zd4bxye

Computer Simulation of the SWI Protocol in Nuclear Magnetic Resonance Imaging [chapter]

Grzegorz Izydorczyk, Artur Klepaczko
2014 Lecture Notes in Computer Science  
SWI is based on field non-uniformity caused by local susceptibility distribution and thus resulting in both measured signal phase shift and faster decay of transverse magnetization vector.  ...  In this paper a design of a computer simulator of susceptibility weighted imaging (SWI) protocol is presented.  ...  Table 1 . 1 Relaxation rates and proton density (PD) parameters Tissue 1.5 T 3 T PD T1 [ms] T2 [ms] T1 [ms] T2 [ms] [a.u.]  ... 
doi:10.1007/978-3-319-11331-9_36 fatcat:l253o2qkfnbkrhenhkwimiolri

Artifacts in 3-T MRI: physical background and reduction strategies

O. Dietrich, M.F. Reiser, S.O. Schoenberg
2008 Clinical imaging  
Magnetic resonance imaging (MRI) at a field strength of 3 Tesla has become more and more frequently used in recent years.  ...  The discussed artifacts are classified and ordered according to the physical mechanism or property of the MRI system responsible for their occurrence: artifacts caused by B0 inhomogeneity and susceptibility  ...  Figure 8 : 8 (a) Gibbs ringing artifacts in T2-weighted 3-Tesla FSE acquisition may be observed as a consequence of the improved signal-to-noise ratio in comparison to 1.5-Tesla MRI; (b) magnified detail  ... 
doi:10.1016/j.clinimag.2008.04.029 fatcat:i3k37xpkq5hcrfr653pf5p2mlu

MR thermometry

Viola Rieke, Kim Butts Pauly
2008 Journal of Magnetic Resonance Imaging  
Accelerated MRI imaging techniques for real-time monitoring with the PRF method will be discussed.  ...  Noninvasive temperature monitoring is feasible with magnetic resonance (MR) imaging based on temperature sensitive MR parameters such as the proton resonance frequency (PRF), the diffusion coefficient  ...  Vogl and Nathan McDannold for providing images of their work for this review. Grant Sponsor: NIH (R01 CA077677, RO1 CA111981, RO1 CA121163)  ... 
doi:10.1002/jmri.21265 pmid:18219673 pmcid:PMC2780364 fatcat:uhdeucv3ebftdazms53kaqkqly

Advantages and pitfalls in 3T MR brain imaging: a pictorial review

Bernd L Schmitz, Andrik J Aschoff, Martin H K Hoffmann, Georg Grön
2005 American Journal of Neuroradiology  
in T2*weighted imaging (Fig 12) .  ...  , changed T1 and T2 relaxation times, decreased T1 tissue contrast, and increased susceptibility effects-render high-field MR imaging more compelling.  ... 
pmid:16219827 pmcid:PMC7976112 fatcat:a6fosknnvnfkzoqbxg4kgyujem

Physiological and Functional Magnetic Resonance Imaging Using Balanced Steady-state Free Precession

Sung-Hong Park, Paul Kyu Han, Seung Hong Choi
2015 Korean Journal of Radiology  
the initial magnetization difference, and good T2* contrast (in case of fMRI).  ...  However, EPI suffers from distortion and signal degradation induced by magnetic field inhomogeneity or susceptibility effects, and it also is subjected to T2* blurring due to the acquisition of multiple  ...  Because of few phase changes in the pass bands (Fig. 3) , the contrast of bSSFP is expected to be closer to T2 rather than T2* (exactly T2/T1).  ... 
doi:10.3348/kjr.2015.16.3.550 pmid:25995684 pmcid:PMC4435985 fatcat:xnh7s3gfc5e3jlhyhbv4flg6hy

Neuro MR: Principles

Timothy P.L. Roberts, David Mikulis
2007 Journal of Magnetic Resonance Imaging  
recalled echo (GRE), and echo planar imaging (EPI).  ...  In particular, the relaxation time constants T 1 , T 2 , and T* 2 are introduced, along with pulse sequences harnessing their contrast, spin-echo, fast spin echo (FSE), inversion recovery (IR), gradient  ...  By suppressing otherwise hyperintense signal from CSF, this T2-weighted image allows delineation of pathologies such as brain tumor (arrow).  ... 
doi:10.1002/jmri.21029 pmid:17685415 fatcat:5zp7aoz6zba4paz67m4sb4ttsm

Water proton MR properties of human blood at 1.5 Tesla: Magnetic susceptibility,T1,T2,T*2, and non-Lorentzian signal behavior

William M. Spees, Dmitriy A. Yablonskiy, Mark C. Oswood, Joseph J.H. Ackerman
2001 Magnetic Resonance in Medicine  
The relaxation parameters AR* and R* 2 increase as a function of the square of the susceptibility difference between red blood cell and plasma and depend on the spin-echo time.  ...  Accurate knowledge of the magnetic properties of human blood is required for the precise modeling of functional and vascular flow-related MRI.  ...  Larry Bretthorst for assistance with the Bayesian analysis software, and Dr. James Schilling for assistance with the SQUID magnetic susceptibility measurements.  ... 
doi:10.1002/mrm.1072 pmid:11283978 fatcat:2a3gev2n2rh25oliwxihigho4i

The importance ofk-space trajectory on off-resonance artifact in segmented echo-planar imaging

Jacob A. Bender, Rizwan Ahmad, Orlando P. Simonetti
2013 Concepts in magnetic resonance. Part A, Bridging education and research  
Theoretical results show off-resonance artifact manifests as a simple positional shift for the top-down trajectory, while for the center-out trajectory off-resonance artifact manifests as a splitting of  ...  Segmented interleaved echo planar imaging (EPI) is a highly efficient data acquisition technique; however, EPI is sensitive to artifacts from off-resonance spins.  ...  This only accounts for off-resonance and not the effects of T2* or motion.  ... 
doi:10.1002/cmr.a.21255 pmid:24358026 pmcid:PMC3864862 fatcat:dxapayaumbfq5ldjcs2bwyi444
« Previous Showing results 1 — 15 out of 5,487 results