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Reconstruction from Projections Imaging
 
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Reconstruction Time
 
Time after completion of examination for the computer to present a digital image.
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• View the DATABASE results for 'Reconstruction Time' (5).Open this link in a new window

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Rectangular Field of View
 
(RFOV) A different field of view (the scanned region) in the frequency and phase encoding directions that means the data acquisition with fewer measurement lines. Because there are fewer rows than columns, a rectangular image is obtained. To reduce the FOV in phase encoding direction (foldover direction) saves scan time by decreasing signal but invariable spatial resolution.
Also called HFI or undersampling.
mri safety guidance
Image Guidance
If the scanned object is oval, e.g. head or abdomen, a rectangular FOV is an easy to use scan parameter to reduce the scan time without loss of resolution.
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• View the DATABASE results for 'Rectangular Field of View' (2).Open this link in a new window

Reference Compound
 
Standard compound used as a standard reference spectral line for defining chemical shifts for a given nucleus. As recommended by the ASTM, for 1H it is tetramethylsilane (TMS) and for 31P it is phosphoric acid, although for practical biological applications water and PCr have been used as secondary references for hydrogen and phosphorus spectroscopy, respectively. The reference compound can be in a capsule outside of the subject (external) or can be in the subject (internal); internal references are generally preferable where possible, as external references may be subject to different conditions.
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Refocused Gradient Echo SequenceInfoSheet: - Sequences -
Intro, Overview, 
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Refocused GRE sequences use a refocusing gradient in the phase encoding direction during the end module to maximize (refocus) remaining xy- (transverse) magnetization at the time when the next excitation is due, while the other two gradients are, in any case, balanced.
When the next excitation pulse is sent into the system with an opposed phase, it tilts the magnetization in the α direction. As a result the z-magnetization is again partly tilted into the xy-plane, while the remaining xy-magnetization is tilted partly into the z-direction.
Companies use different acronyms to describe certain techniques.

Different terms for these gradient echo pulse sequences
R-GRE Refocused Gradient Echo,
FAST Fourier Acquired Steady State,
FFE Fast Field echo,
FISP Fast Imaging with Steady State Precession,
F-SHORT SHORT Repetition Technique Based on Free Induction Decay,
GFEC Gradient Field Echo with Contrast,
GRASS Gradient Recalled Acquisition in Steady State,
ROAST Resonant Offset Averaging in the Steady State,
SSFP Steady State Free Precession.
STERF Steady State Technique with Refocused FID

In this context, 'contrast' refers to the pulse sequence, it does not mean enhancement with a contrast agent.
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• View the DATABASE results for 'Refocused Gradient Echo Sequence' (9).Open this link in a new window

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 [last update: 2024-02-26 03:41:00]