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Gating
 
Synchronization of imaging with a phase of the cardiac or respiratory cycles.
A variety of means for detecting these cycles can be used, such as the ECG, peripheral pulse, chest motion, etc. The synchronization can be prospective or retrospective.
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• Related Searches:
    • Trigger Delay
    • Flow Artifact
    • Cardiac Motion Artifact
    • Cardiac Synchronization
    • Coronary Angiography
 
Further Reading:
  Basics:
Electrocardiogram in an MRI Environment: Clinical Needs, Practical Considerations, Safety Implications, Technical Solutions and Future Directions
Wednesday, 25 January 2012   by cdn.intechopen.com    
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Cardiac Gating
 
This method synchronize the heartbeat with the beginning of the TR, whereat the r wave is used as the trigger. Cardiac gating times the acquisition of MR data to physiological motion in order to minimize motion artifacts. ECG gating techniques are useful whenever data acquisition is too slow to occur during a short fraction of the cardiac cycle.
Image blurring due to cardiac-induced motion occurs for imaging times of above approximately 50 ms in systole, while for imaging during diastole the critical time is of the order of 200-300 ms. The acquisition of an entire image in this time is only possible with using ultrafast MR imaging techniques. If a series of images using cardiac gating or real-time echo planar imaging EPI are acquired over the entire cardiac cycle, pixel-wise velocity and vascular flow can be obtained.
In simple cardiac gating, a single image line is acquired in each cardiac cycle. Lines for multiple images can then be acquired successively in consecutive gate intervals. By using the standard multiple slice imaging and a spin echo pulse sequence, a number of slices at different anatomical levels is obtained. The repetition time (TR) during a ECG-gated acquisition equals the RR interval, and the RR interval defines the minimum possible repetition time (TR). If longer TRs are required, multiple integers of the RR interval can be selected. When using a gradient echo pulse sequence, multiple phases of a single anatomical level or multiple slices at different anatomical levels can be acquired over the cardiac cycle.
Also called cardiac triggering.
 
Images, Movies, Sliders:
 Cardiac Infarct Short Axis Cine Overview  Open this link in a new window
    

Courtesy of  Robert R. Edelman
 Infarct 4 Chamber Cine  Open this link in a new window
    

Courtesy of  Robert R. Edelman
 
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Further Reading:
  Basics:
Cardiac MRI - Technical Aspects Primer
Wednesday, 7 August 2002
Electrocardiogram in an MRI Environment: Clinical Needs, Practical Considerations, Safety Implications, Technical Solutions and Future Directions
Wednesday, 25 January 2012   by cdn.intechopen.com    
Motion-compensation of Cardiac Perfusion MRI using a Statistical Texture Ensemble(.pdf)
June 2003   by www.imm.dtu.dk    
MRI Resources 
Shielding - Breast MRI - Guidance - Used and Refurbished MRI Equipment - Research Labs - MRI Accidents
 
Respiratory Gating
 
Respiratory gating is a respiratory motion reduction technique with reordering of the phase encoding matrix.

See Gating.
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Retrospective Respiratory Gating
 
The resorting of data collected over several acquisitions to create an image where all phase encoding lines are acquired with the object at the same spatial location of the respiratory cycle.
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AIRIS II™InfoSheet: - Devices -
Intro, 
Types of Magnets, 
Overview, 
etc.MRI Resource Directory:
 - Devices -
 
www.hitachimed.com/products/airis_2.asp From Hitachi Medical Systems America Inc.;
the AIRIS II, an entry in the diagnostic category of open MR systems, was designed by Hitachi Medical Systems America Inc. (Twinsburg, OH, USA) and Hitachi Medical Corp. (Tokyo) and is manufactured by the Tokyo branch. A 0.3 T field-strength magnet and phased array coils deliver high image quality without the need for a tunnel-type high-field system, thereby significantly improving patient comfort not only for claustrophobic patients.
Device Information and Specification
CLINICAL APPLICATION
Whole body
CONFIGURATION
Vertical Field, Open MRI
QD Head, MA Head and Neck, QD C-Spine, MA or QD Shoulder, MA CTL Spine, QD Knee, Neck, QD TMJ, QD Breast, QD Flex Body (4 sizes), Small and Large Extrem., QD Wrist, MA Foot and Ankle (WIP), PVA (WIP)
SYNCHRONIZATION
Cardiac gating, ECG/peripheral, respiratory gating (2 modes)
PULSE SEQUENCES
SE, GE, GR, IR, FIR, STIR, FSE, ss-FSE, FLAIR, EPI -DWI, SE-EPI, ms - EPI, SSP, MTC, SARGE, RSSG, TRSG, MRCP, Angiography: CE, 2D/3D TOF
IMAGING MODES
Single, multislice, volume study
TR
SE: 30 - 10,000msec GE: 20 - 10,000msec IR: 50 - 16,700msec FSE: 200 - 16,7000msec
TE
SE : 10 - 250msec IR: 10 -250msec GE: 5 - 50 msec FSE: 15 - 2,000
SINGLE/MULTI SLICE
0.05 sec/image (256 x 256)
FOV
5cm to 42 cm continuous
2D: 2 - 100 mm; 3D: 0.5 - 5 mm
1280 x 1024
MEASURING MATRIX
512 x 512
PIXEL INTENSITY
Level Range: -2,000 to +4,000
Sub millimeter
MAGNET TYPE
Self-shielded, permanent
BORE DIAMETER
or W x H
110 x 43 cm
MAGNET WEIGHT
15,700 kg
H*W*D
79 x 111 x 73 cm
POWER REQUIREMENTS
208/220/240 V, single phase
COOLING SYSTEM TYPE
Air-cooled
STRENGTH
15 mT/m
2.0 m lateral, 2.5 m vert./long
Auto shimming, 3-axis/patient, and volume shim
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MRI Resources 
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