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Refocused Gradient Echo SequenceInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.MRI Resource Directory:
 - Sequences -
 
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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Repetition Time
 
(TR) The amount of time that exists between successive pulse sequences applied to the same slice.
It is delineated by initiating the first RF pulse of the sequence then repeating the same RF pulse at a time t. Variations in the value of TR have an important effect on the control of image contrast characteristics. TR is also a major factor in total scan time.

See also Scan Time and Image Contrast Characteristics.
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Further Reading:
  Basics:
Magnetic resonance imaging
   by www.scholarpedia.org    
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    
  News & More:
A short-TR single-echo spin-echo breath-hold method for assessing liver T2
Sunday, 10 December 2023   by link.springer.com    
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Saturation Recovery
 
(SR) Particular type of partial saturation pulse sequence in which the preceding pulses leave the spins in a state of saturation, so that recovery at the time of the next pulse has taken place from an initial condition of no magnetization. A rare used MRI pulse sequence that generates a predominantly proton density dependent signal, basically employing a 90° RF excitation pulse, with a very long repetition time. With this technique T1 times can be measured faster than with inversion recovery pulse sequences.
This saturation recovery sequence consists of multiple 90° radio frequency (RF) pulses with a short repetition time. A spoiler gradient pulse dephases the longitudinal magnetization that remains after the first 90° radio frequency pulse. A repetition time interval after the application of this spoiling gradient turns an additional 90° pulse the new developed longitudinal magnetization into the transverse plane, followed by recording a gradient echo.
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Further Reading:
  Basics:
Contrast mechanisms in magnetic resonance imaging
2004   by www.iop.org    
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Signa 3.0T™InfoSheet: - Devices -
Intro, 
Types of Magnets, 
Overview, 
etc.MRI Resource Directory:
 - Devices -
 
www.gehealthcare.com/usen/mr/s_excite3/index.html (Signa VH/i 3.0T)
With GE Healthcare leading-edge technology in ultra-high-field imaging. The 3 T VH/i provides a platform for advanced applications in radiology, cardiology, psychology and psychiatry. Real-time image processing lets you acquire multislice whole brain images and map brain functions for research or surgical planning. And the 3 T Signa VH/i is flexible enough to provide clinicians with high performance they require. It can provide not only outstanding features in brain scanning and neuro-system research, but also a wide range of use in scanning breasts, extremities, the spine and the cardiovascular systems.
Device Information and Specification
CLINICAL APPLICATION
Whole body
CONFIGURATION
Cylindrical - high homogeneity
T/R quadrature head, T/R quadrature body, T/R phased array extremity (opt)
SYNCHRONIZATION
ECG/peripheral, respiratory gating
PULSE SEQUENCES
SE, IR, 2D/3D GRE, FGRE, RF-spoiled GRE, FSE, Angiography: 2D/3D TOF, 2D/3D phase contrast vascular
IMAGING MODES
Single, multislice, volume study, fast scan, multi slab, cine, localizer
SINGLE SLICE
100 Images/sec with Reflex100
MULTISLICE
100 Images/sec with Reflex100
1 cm to 40 cm continuous
2D 0.5-100mm in 0.1mm incremental
1280 x 1024
MEASURING MATRIX
128x512 steps 32 phase encode
PIXEL INTENSITY
256 gray levels
55cm
MAGNET WEIGHT
15102 kg incl. cryogen's
H*W*D
260cm x 238cm x 265cm
POWER REQUIREMENTS
480 or 380/415, 3 phase ||
COOLING SYSTEM TYPE
Closed-loop water-cooled grad.
Less than 0.14 L/hr liquid He
STRENGTH
40mT/m
5-GAUSS FRINGE FIELD, radial/axial
5.4 m x 3.2 m
Superconductive + hi order active
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Signa Contour/i 0.5T™InfoSheet: - Devices -
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www.gemedical.co.kr/rad/mri/products/contour/contouri.html From GE Healthcare;
GE's Signa Contour/i system uses the innovations like K4 technology and real-time interactive imaging. This compact magnet with wide-flare gantry obtains high patient comfort with low costs.
Device Information and Specification
CLINICAL APPLICATION
Whole body
CONFIGURATION
Compact
Head and body coil standard; all other coils optional; open architecture makes system compatible with a wide selection of coils
SYNCHRONIZATION
ECG/peripheral, respiratory gating
PULSE SEQUENCES
Standard: SE, IR, 2D/3D GRE and SPGR, Angiography;; 2D/3D TOF, 2D/3D Phase Contrast;; 2D/3D FSE, 2D/3D FGRE and FSPGR, SSFP, FLAIR, optional: EPI, 2D/3D Fiesta, FGRET, Spiral
IMAGING MODES
Localizer, single slice, multislice, volume, fast, POMP, multi slab
1 cm to 48 cm continuous
2D 0.8 mm to 20 mm; 3D 0.1 mm to 5 mm
1280 x 1024
MEASURING MATRIX
128x512 steps 32 phase encode
PIXEL INTENSITY
256 gray levels
POWER REQUIREMENTS
480 or 380/415 V
COOLING SYSTEM TYPE
Closed-loop water-cooled gradient
STRENGTH
SmartSpeed 23 mT/m, HiSpeed Plus 33 mT/m
Active
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