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Result : Searchterm 'ffe' found in 17 terms [] and 429 definitions []
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Searchterm 'ffe' was also found in the following services: 
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Chemical Shift 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
Chemical shift, black boundary, spatial misregistration, relief
DESCRIPTION
Black or bright band
During frequency encoding, fat protons precess slower than water protons in the same slice because of their magnetic shielding. Through the difference in resonance frequency between water and fat, protons at the same location are misregistrated (dislocated) by the Fourier transformation, when converting MRI signals from frequency to spatial domain. This chemical shift misregistration cause accentuation of any fat-water interfaces along the frequency axis and may be mistaken for pathology. Where fat and water are in the same location, this artifact can be seen as a bright or dark band at the edge of the anatomy.
Protons in fat and water molecules are separated by a chemical shift of about 3.5 ppm. The actual shift in Hertz (Hz) depends on the magnetic field strength of the magnet being used. Higher field strength increases the misregistration, while in contrast a higher gradient strength has a positive effect. For a 0.3 T system operating at 12.8 MHz the shift will be 44.8 Hz compared with a 223.6 Hz shift for a 1.5 T system operating at 63.9 MHz.
mri safety guidance
Image Guidance
For artifact reduction helps a smaller water fat shift (higher bandwidth), a higher matrix, an in phase TE or a spin echo technique. Since the misregistration offset is present in the read out axis the patient may be rescanned with this axis parallel to the fat-water interface. Steeper gradient may be employed to reduce the chemical shift offset in mm. Another strategy is to employ specialized pulse sequences such as fat saturation or inversion recovery imaging. Fat suppression techniques eliminate chemical shift artifacts caused by the lack of fat signal.

See also Black Boundary Artifact and Magnetic Resonance Spectroscopy.
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• Related Searches:
    • Bandwidth
    • Spatial Misregistration Artifact
    • Opposed Phase Image
    • In Phase
    • Chemical Shift Spatial Offset
 
Further Reading:
  Basics:
MRI Artifact Gallery
   by chickscope.beckman.uiuc.edu    
  News & More:
What is chemical shift artefact? Why does it occur? How many Hz at 1.5 T?
   by www.revisemri.com    
Abdominal MRI at 3.0 T: The Basics Revisited
Wednesday, 20 July 2005   by www.ajronline.org    
MRI Resources 
DICOM - Devices - Patient Information - Colonography - Corporations - Crystallography
 
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    
MRI Resources 
Stent - Shielding - Chemistry - Research Labs - Non-English - Jobs pool
 
Contrast to Noise Ratio
 
(CNR) In Magnetic Resonance Imaging MRI, Contrast to noise ratio is the relationship of signal intensity differences between two regions, scaled to image noise. Improving CNR increases perception of the distinct differences between two clinical areas of interest. A contrast to noise ratio is a summary of SNR and contrast. It is the difference in SNR between two relevant tissue types.
(A and B): CNR = SNRA - SNRB

See also Signal Intensity, Signal to Noise Ratio and Medical Imaging.
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• View the DATABASE results for 'Contrast to Noise Ratio' (2).Open this link in a new window


• View the NEWS results for 'Contrast to Noise Ratio' (1).Open this link in a new window.
 
Further Reading:
  Basics:
Vascular Filters of Functional MRI: Spatial Localization Using BOLD and CBV Contrast
Contrast mechanisms in magnetic resonance imaging
2004   by www.iop.org    
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    
Searchterm 'ffe' was also found in the following services: 
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News  (436)  Resources  (66)  Forum  (134)  
 
Corrupted Data (Artifact)InfoSheet: - Artifacts - 
Case Studies, 
Reduction Index, 
etc.MRI Resource Directory:
 - Contrast Agents -
 
Quick Overview
Artifact Information
NAME
Corrupted data
DESCRIPTION
Incorrectly interpretation or display
REASON
Corrupted data
HELP
Save to a new or different media
An artifact on a MR image can appear when data read off an optical disc became corrupted. There two effects can be seen.
Firstly, Bands where the intensity has been incorrectly interpreted or secondly areas, where the horizontal position of the pixels has been incorrectly displayed. It is important to be able to differentiate between artifacts caused during a MRI scan, from those caused by the associated hardware of an imaging system.
mri safety guidance
Image Guidance
Review the hardware and store the images on a new disc.
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Further Reading:
  Basics:
MRI Artifact Gallery
   by chickscope.beckman.uiuc.edu    
MRI Resources 
Functional MRI - Manufacturers - Knee MRI - Libraries - Journals - MR Guided Interventions
 
Diffusion Tensor ImagingInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.MRI Resource Directory:
 - Diffusion Weighted Imaging -
 
(DTI) Diffusion tensor imaging is the more sophisticated form of DWI, which allows for the determination of directionality as well as the magnitude of water diffusion. This kind of MR imaging can estimates damage to nerve fibers that connect the area of the brain affected by the stroke to brain regions that are distant from it, and can be used to determine the effectiveness of stroke prevention medications.
DTI (FiberTrak) enables to visualize white matter fibers in the brain and can map (trace image) subtle changes in the white matter associated with diseases such as multiple sclerosis and epilepsy, as well as assessing diseases where the brain's wiring is abnormal, such as schizophrenia.
The fractional anisotropy (FA) gives information about the shape of the diffusion tensor at each voxel. The FA is based on the normalized variance of the eigenvalues. The fractional anisotropy reflects differences between an isotropic diffusion and a linear diffusion. The FA range is between 0 and 1 (0 = isotropic diffusion, 1 = highly directional).
The development of new imaging methods and some useful analysis techniques, such as 3-dimensional anisotropy contrast (3DAC) and spatial tracking of the diffusion tensor tractography (DTT), are currently under study.
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• View the DATABASE results for 'Diffusion Tensor Imaging' (9).Open this link in a new window


• View the NEWS results for 'Diffusion Tensor Imaging' (2).Open this link in a new window.
 
Further Reading:
  Basics:
EVALUATION OF HUMAN STROKE BY MR IMAGING
2000
  News & More:
What MRI-Derived Data and Other Factors Reveal About White Matter Hyperintensity in Former Football Players
Saturday, 23 December 2023   by www.diagnosticimaging.com    
Effect of gadolinium-based contrast agent on breast diffusion-tensor imaging
Thursday, 6 August 2020   by www.eurekalert.org    
Learning difficulties linked to poor brain connectivity
Monday, 2 March 2020   by cosmosmagazine.com    
New imaging technique reveals early brain damage caused by hypertension
Friday, 18 September 2015   by www.medicalnewstoday.com    
Imaging shows structural changes in mild traumatic brain injury
Thursday, 25 October 2007   by www.eurekalert.org    
MRI Resources 
MRI Technician and Technologist Schools - Pregnancy - Movies - MRI Technician and Technologist Jobs - Developers - Research Labs
 
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