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 'Image Guidance' 
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Result : Searchterm 'Image Guidance' found in 0 term [] and 54 definitions []
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Searchterm 'Image Guidance' was also found in the following service: 
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News  (3)  
 
Crisscross / Herringbone ArtifactInfoSheet: - Artifacts - 
Case Studies, 
Reduction Index, 
etc.MRI Resource Directory:
 - Artifacts -
 
Quick Overview
Please note that there are different common names for this artifact.

Artifact Information
NAME Crisscross, Herringbone
DESCRIPTION Crisscross or herringbone structures throughout the image
REASON Hardware failure
HELP Call the service

This artifact appears as a herringbone pattern scattered over the whole image in any direction only on one slice or on multiple slices. The causes of this are many and various, like e.g. electromagnetic spikes created by the gradients, electronic equipment inside the MR procedure room, or fluctuating AC current.


Image Guidance
Sometimes it is sufficient to change flickering light bulbs. If the problem increases or keeps on existing, it should be addressed by a service representative.

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MRI Resources 
Sequences - Functional MRI - Absorption and Emission - Software - Blood Flow Imaging - Movies
 
Crosstalk (Artifact)InfoSheet: - Artifacts - 
Case Studies, 
Reduction Index, 
etc.MRI Resource Directory:
 - Artifacts -
 
Quick Overview

Artifact Information
NAME Crosstalk, cross excitation
DESCRIPTION Anomalous intensities in an image
REASON Interference
HELP Slice gap minimum 10%

Crosstalk is an artifact introduced into images by interference between adjacent slices of a scan, caused by a slice profile that is not ideal due to the constraints of the measurement technology. If the slice distances are too small, there is cross talk between the slices, which can affect T1 contrast.


Image Guidance
This artifact can be eliminated by limiting the minimum spacing (for the most sequences a minimum gap 10% and for IR sequences 20%) between the slices. Crosstalk can also be reduced by selection of interleaved slices (so a slice gap will not be necessary), but interleaved data acquisition can produce large mean intensity differences between adjacent slices.

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• View the DATABASE results for 'Crosstalk (Artifact)' (2).Open this link in a new window

 
Further Reading:
  Basics:
MRI GLOSSARY
   by fonar.com    
Slice-overlap Artifacts
   by www.mritutor.org    
MRI Resources 
MR Myelography - Journals - MRCP - MRI Reimbursement - Case Studies - Spectroscopy
 
Digitization Noise ArtifactInfoSheet: - Artifacts - 
Case Studies, 
Reduction Index, 
etc.MRI Resource Directory:
 - Artifacts -
 
Quick Overview
Please note that there are different common names for this artifact.

Artifact Information
NAME Digitization noise, digitizer quantization, low dynamic range
DESCRIPTION Noise
REASON Finite voltage resolution of the digitizer
HELP Larger range of sensitivity

Noise introduced into digitized signals by the finite voltage resolution of the digitizer.
You can see the effects of quantization if the noise level is smaller than the digitizer quantum. If the signal dynamic range is too great, the highest intensities from overloading the digitizer may result in the weaker features being lost in the digitization noise.


Image Guidance
This can be resolved by using an analog to digital converter with a larger range of sensitivity or by using techniques to reduce the dynamic range, e.g. suppressing the signal from water in order to detect the signal from less abundant compounds.

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• View the DATABASE results for 'Digitization Noise Artifact' (2).Open this link in a new window

 
Further Reading:
  Basics:
MRI Artifact Gallery
   by chickscope.beckman.uiuc.edu    
Searchterm 'Image Guidance' was also found in the following service: 
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News  (3)  
 
Eddy Current ArtifactInfoSheet: - Artifacts - 
Case Studies, 
Reduction Index, 
etc.
 
Quick Overview

Artifact Information
NAME Eddy current
DESCRIPTION Image distortion
REASON Induced by changes in a magnetic field
HELP Eddy current compensation, shielding

Eddy currents can cause artifacts in images and may seriously degrade overall magnet performance.


Image Guidance
Common uses to reduce the influence of eddy currents on gradient fields are eddy current compensation and shielded gradient coils (active or passive). If persistent, it must be addressed by a service representative to verify the magnet performance.
See also Eddy Current Compensation.

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• View the DATABASE results for 'Eddy Current Artifact' (2).Open this link in a new window

 
Further Reading:
  Basics:
Generic Eddy Current Compensation for Rapid Magnetic Resonance Imaging(.pdf)
   by www.switt.ch    
MRI Resources 
Libraries - MRA - Knee MRI - MRCP - MRI Physics - Implant and Prosthesis
 
FID Signal ArtifactInfoSheet: - Artifacts - 
Case Studies, 
Reduction Index, 
etc.MRI Resource Directory:
 - Artifacts -
 
Quick Overview

Artifact Information
NAME FID (with spin echo) signal
DESCRIPTION Line across the center of the image
REASON Combination of problems
HELP Call the service

A combination of B1 inhomogeneity, poor slice profile, and insufficient spoiler gradients between the refocusing pulse and the readout interval of a spin echo sequence results in a FID signal being detected along with the echo.
Since the FID is not phase encoded (normally the phase encoding occurs before the refocusing pulse), it is not dispersed along the phase encoding axis, but appears as a line across the center of the image.


Image Guidance
If the problem persists, it must be addressed by a service representative.
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• View the DATABASE results for 'FID Signal Artifact' (2).Open this link in a new window

 
Further Reading:
  News & More:
MRI Artifact Gallery
   by chickscope.beckman.uiuc.edu    
MRI Resources 
Anatomy - Software - MRI Accidents - MRI Training Courses - Colonography - Contrast Enhanced MRI
 
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Acoustic Noise Reduction (Silent, Quiet, etc.) :
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is in its first steps 
is done by earplugs, headphones 
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