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Result : Searchterm 'Gradient Echo Sequence' found in 5 terms [] and 80 definitions []
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Flip Angle
 
(FA) The flip angle a is used to define the angle of excitation for a field echo pulse sequence. It is the angle to which the net magnetization is rotated or tipped relative to the main magnetic field direction via the application of a RF excitation pulse at the Larmor frequency. It is also referred to as the tip angle, nutation angle or angle of nutation.
The radio frequency power (which is proportional to the square of the amplitude) of the pulse is proportional to a through which the spins are tilted under its influence. Flip angles between 0° and 90° are typically used in gradient echo sequences, 90° and a series of 180° pulses in spin echo sequences and an initial 180° pulse followed by a 90° and a 180° pulse in inversion recovery sequences.
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• Related Searches:
    • Net Magnetization Vector
    • Precess
    • Abdominal Imaging
    • Echo
    • Out of Phase
 
Further Reading:
  Basics:
What MRI Sequences Produce the Highest Specific Absorption Rate (SAR), and Is There Something We Should Be Doing to Reduce the SAR During Standard Examinations?
Thursday, 16 April 2015   by www.ajronline.org    
Mapping of low flip angles in magnetic resonance(.pdf)
Saturday, 1 January 2011   by www.hal.inserm.fr    
  News & More:
A practical guideline for T1 reconstruction from various flip angles in MRI
Saturday, 1 October 2016   by journals.sagepub.com    
Clinical evaluation of a speed optimized T2 weighted fast spin echo sequence at 3.0 T using variable flip angle refocusing, half-Fourier acquisition and parallel imaging
Wednesday, 25 October 2006
MRI Resources 
Contrast Enhanced MRI - MRI Reimbursement - Brain MRI - Cochlear Implant - Online Books - Hospitals
 
Flow Related Enhancement
 
(FRE) Flow related enhancement could be seen most for blood flow, but also for other liquids with some MR imaging techniques, as an increase in intensity due to the washout of saturated spins. FRE provides positive contrast ("bright blood") of vascular details in time of flight MRA as well as the physiologic characterization of blood flow.
If stationary spins within the scanned region experience only an incomplete T1 relaxation between the repeated radio frequency (RF) excitations, this results in fewer signal of the stationary tissue (compared to inflowing blood with completely relaxed spins). The degree of the flow related enhancement is proportional to the blood flow velocity and the used repetition time. The use of flow compensation (gradient moment nulling) improves the FRE especially in gradient echo sequences.
 
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Further Reading:
  Basics:
Conventional MRI and MR Angiography of Stroke
2012   by www.mc.vanderbilt.edu    
MRI Resources 
Health - PACS - RIS - Libraries - Blood Flow Imaging - Guidance
 
Flow VoidForum -
related threads
 
The occurrence of a low signal in regions of flow. For a spin echo sequence, this is caused in part by a lack of refocusing of blood, which is excited by the 90° pulse but not by the 180° pulse. For a gradient echo sequence, this is caused by the dephasing of blood signal.
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Further Reading:
  Basics:
MRI Artifacts, Flow void and Signal void
   by www.neuroradiologycases.com    
Flow comp off: An easy technique to confirm CSF flow within syrinx and aqueduct
Wednesday, 2 January 2013   by medind.nic.in    
DRIVE: shorter scan time, brighter fluid
   by clinical.netforum.healthcare.philips.com    
Searchterm 'Gradient Echo Sequence' was also found in the following services: 
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Gradient Echo Multi SliceInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.
 
(GEMS) This pulse sequence uses a changeable flip angle instead of a 90° pulse and a gradient instead of a RF pulse to rephase the FID.
T2*, T1 weighted and proton density images can be acquired. The flip angle in combination with the TR determines the T1 weighting and the TE controls the amount of dephasing. To minimize T2* the echo time should be short.
See also Gradient Echo Sequence.
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Gradient Echo SpectroscopyInfoSheet: - Sequences - 
Intro, 
Overview, 
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 - Spectroscopy pool -
 
(GES) See Gradient Echo Sequence and Spectroscopy.
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MRI Resources 
MR Myelography - Raman Spectroscopy - Safety Training - Blood Flow Imaging - Software - Homepages
 
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