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Acquisition Matrix
 
The total number of independent data samples in the frequency and phase directions (number of pixels in the frequency encoding - and phase encoding direction).
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    • Matrix Size
    • Gibbs Artifact
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Rapid Acquisition Matrix FASTInfoSheet: - Sequences - 
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Overview, 
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(RAM-FAST) A fast gradient echo pulse sequence using a magnetization preparation pulse.

See Ultrafast Gradient Echo Sequence.
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Gibbs ArtifactInfoSheet: - Artifacts - 
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Quick Overview
Please note that there are different common names for this MRI artifact.
Artifact Information
NAME
Gibbs, Gibbs ringing, truncation
DESCRIPTION
Edge ringing, syrinx-like stripe
REASON
Sharp changes in intensity (incomplete digitization of the echo)
HELP
More samples
The Gibbs or ringing artifact appears as a series of lines in the MR image parallel to abrupt and intense changes in the object at this location. This artifact does not occur visibly on smooth objects. This artifact is caused by the Gibbs phenomenon, an overshoot or ringing of Fourier series occurring at discontinuities.
In the spinal cord, a small syrinx can be simulated by the Gibbs phenomenon. Gibbs artifacts are also seen in other regions, for example the brain//skull interface.
Fine lines visible in an image may be due to undersampling of the high spatial frequencies, respectively incomplete digitization of the echo.
With more encoding steps the Gibbs artifacts is less intense and narrower. Therefore, e.g. the artifact is more intense in the 256 point dimension of a 256x512 acquisition matrix.
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Image Guidance
This problem can only be resolved by smoothing filters (LanczosSigmaFactor, 2-D Exponential Filtering, Gegenbauer Reconstruction etc.) or with a higher acquisition matrix and/or a smaller FOV, to smooth the object.

See also Gibbs Phenomenon and Apodization.
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Further Reading:
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Lanczos sigma Factor
   by mathworld.wolfram.com    
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Troubleshooting the ACR MRI Accreditation Phantom Tests
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AcquisitionsForum -
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The process of measuring and storing image data.

See also Acquisition Matrix, Acquisition Time.
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Further Reading:
  Basics:
Optimal k-Space Sampling for Dynamic Contrast-Enhanced MRI with an Application to MR Renography
Thursday, 5 November 2009   by www.ncbi.nlm.nih.gov    
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    
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Annotation
 
A description of the factors used in creating an image should include the type and times of the pulse sequence, the number of signals averaged or added (NSA), the size of the reconstructed region, the size of the acquisition matrix in each direction, field of view and the slice thickness; usually printed at the border of MRI pictures.
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