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Result : Searchterm 'Excitation' found in 10 terms [] and 86 definitions []
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Constructive Interference Steady StateInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.
 
(CISS) This gradient echo sequence is a stimulated T2 echo. Two TrueFISP sequences are acquired with differing RF pulses and than combined for strong T2 Weighted high resolution 3D images.
These TrueFISP sequences are normally affected by dark phase dispersion bands, which are caused by patient induced local field inhomogeneities and made prominent by the relatively long TR used. The different excitation pulse regimes offset these bands in the 2 sequences. Combining the images results in a picture free of banding. The image combination is performed automatically after data collection, adding some time to the reconstruction process. The advantage of the 3D CISS sequence is its combination of high signal levels and extremely high spatial resolution.
Used for, e.g. inner ear, cranial nerves and cerebellum.

See also Steady State Free Precession.
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Further Reading:
  News & More:
Pediatric and Adult Cochlear Implantation1
2003   by radiographics.rsnajnls.org    
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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
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.
mri safety guidance
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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Further Reading:
  Basics:
MRI GLOSSARY
   by fonar.com    
Slice-overlap Artifacts
   by www.mritutor.org    
MRI Resources 
DICOM - Services and Supplies - Devices - Anatomy - Diffusion Weighted Imaging - Veterinary MRI
 
EchoForum -
related threads
 
In MRI, an echo is the emission of energy in form of an electromagnetic resonance signal of a nuclei after its excitation. At this point spins are back in phase again and the signal is measured. The desired number of echoes is selectable. Often until eight echoes are permissible for 2D or 3D scans using spin echo, inversion recovery or MIX techniques. Two echoes are permissible for all other techniques. A multi echo imaging sequence is needed for simultaneous measurement of T2 and density weighted images.
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Further Reading:
  News & More:
Ultrashort echo time (UTE) MRI of the spine in thalassaemia
February 2004   by bjr.birjournals.org    
UCLA chemists use MRI to peek at temperatures of gases inside catalytic reactors
Thursday, 24 October 2013   by esciencenews.com    
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Echo Offset
 
Echo offset is the time setting of spin echo and gradient echo to be not coincident and to generate phase differences between different spectral line signals (e.g., water and fat). The echo offset is the product of the frequency line difference and the time difference (TD) in the echo times and is equal to the magnitude of the result of the phase difference between two spectral lines. Phases may not change linearly with echo offset time in the presence of a large field inhomogeneity. An echo offset excitation pulse sequence can be used in the magnetic field mapping method, to generate maps from which the standard deviation of the phase difference can be calculated.
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Further Reading:
  News & More:
T1rho-prepared balanced gradient echo for rapid 3D T1rho MRI
Monday, 1 September 2008   by www.ncbi.nlm.nih.gov    
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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Echo Planar Imaging Factor
 
(EPI Factor) The imaging speed in Echo Planar Imaging (EPI) depends on many factors. Single shot EPI should provide images within 100 ms or less. Because of this limitations, a multi shot EPI approach is in most cases preferred. The parameter 'EPI Factor' is used to specify the number of k-space profiles collected per excitation.
The EPI factor 64 means a measurement time 64 times faster than a normal gradient echo sequence. See also Echo Planar Imaging.
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Further Reading:
  Basics:
Echo Planar Imaging at 4 Tesla With Minimum Acoustic Noise(.pdf)
   by www.bnl.gov    
Echo-planar imaging (EPI) and functional MRI(.pdf)
1998   by www.uib.no    
MRI Resources 
Stimulator pool - Online Books - RIS - Used and Refurbished MRI Equipment - Implant and Prosthesis pool - Liver Imaging
 
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