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Find video protocols related to scientific articles indexed in Pubmed.
MR imaging of the fetal brain at 1.5T and 3.0T field strengths: comparing specific absorption rate (SAR) and image quality.
J Perinat Med
PUBLISHED: 08-06-2014
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Abstract Objectives: Our two objectives were to evaluate the feasibility of fetal brain magnetic resonance imaging (MRI) using a fast spin echo sequence at 3.0T field strength with low radio frequency (rf) energy deposition (as measured by specific absorption rate: SAR) and to compare image quality, tissue contrast and conspicuity between 1.5T and 3.0T MRI. Methods: T2 weighted images of the fetal brain at 1.5T were compared to similar data obtained in the same fetus using a modified sequence at 3.0T. Quantitative whole-body SAR and normalized image signal to noise ratio (SNR), a nominal scoring scheme based evaluation of diagnostic image quality, and tissue contrast and conspicuity for specific anatomical structures in the brain were compared between 1.5T and 3.0T. Results: Twelve pregnant women underwent both 1.5T and 3.0T MRI examinations. The image SNR was significantly higher (P=0.03) and whole-body SAR was significantly lower (P<0.0001) for images obtained at 3.0T compared to 1.5T. All cases at both field strengths were scored as having diagnostic image quality. Images from 3.0T MRI (compared to 1.5T) were equal (57%; 21/37) or superior (35%; 13/37) for tissue contrast and equal (61%; 20/33) or superior (33%, 11/33) for conspicuity. Conclusions: It is possible to obtain fetal brain images with higher resolution and better SNR at 3.0T with simultaneous reduction in SAR compared to 1.5T. Images of the fetal brain obtained at 3.0T demonstrated superior tissue contrast and conspicuity compared to 1.5T.
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MR venography of the fetal brain using susceptibility weighted imaging.
J Magn Reson Imaging
PUBLISHED: 07-04-2014
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To evaluate the feasibility of performing fetal brain magnetic resonance venography using susceptibility weighted imaging (SWI).
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Improved MR venography using quantitative susceptibility-weighted imaging.
J Magn Reson Imaging
PUBLISHED: 06-14-2014
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To remove the geometry dependence of phase-based susceptibility weighting masks in susceptibility-weighted imaging (SWI) and to improve the visualization of the veins and microbleeds.
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Susceptibility mapping of air, bone, and calcium in the head.
Magn Reson Med
PUBLISHED: 06-11-2014
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To demonstrate the mapping of structures with high susceptibility values, such as the sinuses, bones and teeth, using short echo times.
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Measuring venous blood oxygenation in fetal brain using susceptibility-weighted imaging.
J Magn Reson Imaging
PUBLISHED: 05-01-2014
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To evaluate fetal cerebral venous blood oxygenation, Yv, using principles of MR susceptometry.
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Quantitative T2 changes and susceptibility-weighted magnetic resonance imaging in murine pregnancy.
Gynecol. Obstet. Invest.
PUBLISHED: 01-13-2014
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To evaluate gestational age-dependent changes in the T2 relaxation time in normal murine placentas in vivo. The role of susceptibility-weighted imaging (SWI) in visualization of the murine fetal anatomy was also elucidated.
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Eu(II)-containing cryptates as contrast agents for ultra-high field strength magnetic resonance imaging.
Chem. Commun. (Camb.)
PUBLISHED: 11-02-2011
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The relaxivity (contrast-enhancing ability) of Eu(II)-containing cryptates was found to be better than a clinically approved Gd(III)-based agent at 7 T. These cryptates are among a few examples of paramagnetic substances that show an increase in longitudinal relaxivity, r(1), at ultra-high field strength relative to lower field strengths.
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Quantifying effective magnetic moments of narrow cylindrical objects in MRI.
Phys Med Biol
PUBLISHED: 11-04-2009
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A new procedure for accurately measuring effective magnetic moments of long cylinders is presented. Partial volume, dephasing and phase aliasing effects are naturally included and overcome in our approach. Images from a typical gradient echo sequence at one single echo time are usually sufficient to quantify the effective magnetic moment of a cylindrical-like object. Only pixels in the neighborhood of the object are needed. Our approach can accurately quantify the magnetic moments and distinguish subpixel changes of cross sections between cylindrical objects. Uncertainties of our procedure are studied through the error propagation method. Images acquired with different parameters are used to test the robustness of our method. Alternate approaches and their limitations to extract magnet moments of objects with different orientations are also discussed. Our method has the potential to be applied to any long object whose cross section is close to a disk.
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Imaging the vessel wall in major peripheral arteries using susceptibility-weighted imaging.
J Magn Reson Imaging
PUBLISHED: 07-25-2009
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To demonstrate a novel contrast mechanism for imaging the vessel wall and vessel wall calcification using susceptibility-weighted imaging (SWI).
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Removing background phase variations in susceptibility-weighted imaging using a fast, forward-field calculation.
J Magn Reson Imaging
PUBLISHED: 03-24-2009
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To estimate magnetic field variations induced from air-tissue interface geometry and remove their effects from susceptibility-weighted imaging (SWI) data.
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Limitations of calculating field distributions and magnetic susceptibilities in MRI using a Fourier based method.
Phys Med Biol
PUBLISHED: 01-30-2009
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A discrete Fourier based method for calculating field distributions and local magnetic susceptibility in MRI is carefully studied. Simulations suggest that the method based on discrete Greens functions in both 2D and 3D spaces has less error than the method based on continuous Greens functions. The 2D field calculations require the correction of the Lorentz disk, which is similar to the Lorentz sphere term in the 3D case. A standard least-squares fit is proposed for the extraction of susceptibility for a single object from MR images. Simulations and a phantom study confirm both the discrete method and the feasibility of the least-squares fit approach. Finding accurate susceptibility values of local structures in the brain from MR images may be possible with this approach in the future.
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Catalytic multiecho phase unwrapping scheme (CAMPUS) in multiecho gradient echo imaging: removing phase wraps on a voxel-by-voxel basis.
Magn Reson Med
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Phase images reflect local field variations including susceptibility contributions and play a key role in a number of imaging applications. However, due to the limited dynamic range of phase values, phase wrapping invariably occurs at long echo times. High pass filtering and region-growing approaches have been common themes in the effort of removing phase wraps. In this article, a novel voxel-by-voxel phase unwrapping scheme taking advantage of short interecho spacing of multiecho gradient echo imaging is proposed. By removing spurious sources of phase variations and exploiting the special features of the flow-induced phase component, phase increments during adjacent echoes can be unveiled that exhibit no phase aliasing. This unaliased phase information is then used to unwrap all the phase images at all of the echoes. Data of 15 volunteers scanned at 3 and 1.5T were processed with the proposed algorithm and two other algorithms in the literature (PhUN and branch cut). It is shown that the proposed approach is fast and effective in unwrapping all the phase values even for voxels in the eyes and the skull, which the other algorithms failed to unwrap. Thus, in multiecho gradient echo imaging, the proposed algorithm has major potential in various applications involving phase processing.
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Quantitative susceptibility mapping of small objects using volume constraints.
Magn Reson Med
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Microbleeds have been implicated to play a role in many neurovascular and neurodegenerative diseases. The diameter of each microbleed has been used previously as a possible quantitative measure for grading microbleeds. We propose that magnetic susceptibility provides a new quantitative measure of extravasated blood. Recently, a Fourier-based method has been used that allows susceptibility quantification from phase images for any arbitrarily shaped structures. However, when very small objects, such as microbleeds, are considered, the accuracy of this susceptibility mapping method still remains to be evaluated. In this article, air bubbles and glass beads are taken as microbleed surrogates to evaluate the quantitative accuracy of the susceptibility mapping method. We show that when an object occupies only a few voxels, an estimate of the true volume of the object is necessary for accurate susceptibility quantification. Remnant errors in the quantified susceptibilities and their sources are evaluated. We show that quantifying magnetic moment, rather than the susceptibility of these small structures, may be a better and more robust alternative.
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What is Visualize?

JoVE Visualize is a tool created to match the last 5 years of PubMed publications to methods in JoVE's video library.

How does it work?

We use abstracts found on PubMed and match them to JoVE videos to create a list of 10 to 30 related methods videos.

Video X seems to be unrelated to Abstract Y...

In developing our video relationships, we compare around 5 million PubMed articles to our library of over 4,500 methods videos. In some cases the language used in the PubMed abstracts makes matching that content to a JoVE video difficult. In other cases, there happens not to be any content in our video library that is relevant to the topic of a given abstract. In these cases, our algorithms are trying their best to display videos with relevant content, which can sometimes result in matched videos with only a slight relation.