Magnetic Resonance - Technology Information Portal Welcome to MRI Technology••


Acoustic Noise Reduction (Silent, Quiet, etc.) :
cannot get better 
is in its first steps 
is done by earplugs, headphones 
must get better 
is bad, I miss something 
is unnecessary 

MRI Artifacts
Ultrasound Imaging Artifacts Open this link in a new window
Artifact Reduction
- Cardiac Motion
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.

• View the DATABASE results for 'Cardiac Gating' (15).Open this link in a new window

Further Reading:
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    
Motion-compensation of Cardiac Perfusion MRI using a Statistical Texture Ensemble(.pdf)
June 2003   by    
Synchronization, Cardiac 
Acquiring images of particular phases of the cardiac cycle, through either retrospective or prospective synchronization. Also called cardiac gating.
Synchronization, Prospective 
Controlling the timing or sequence of image data acquisition according to the phase of respiratory or cardiac cycles.
Synchronization, Retrospective 
Sorting and possibly adjusting image data acquired asynchronously with the cardiac or respiratory cycle, according to the phase of the cycle at which it was acquired, so as to reconstruct a set of images corresponding to different phases of the cycle.
  Artifacts - Reduction Index - Respiratory Motion top

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 [last update: 2018-03-08 05:11:00]