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Slice Profile
 
The spatial distribution of sensitivity of the imaging process in the direction perpendicular to the plane of the slice. When the profile deviates appreciably from rectangular, the slice thickness alone may not provide an adequate description.
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MRI Resources 
Blood Flow Imaging - - DICOM - Spine MRI - Safety Training - Guidance
 
Slice Thickness
 
(THK) The thickness of an imaging slice. As the slice profile may not be sharp edged, a criterion such as the distance between the points at half the sensitivity of the maximum (FWHM) or the equivalent rectangular width (the width of a rectangular slice profile with the same maximum height and same area) is used to determine thickness.


Image Guidance
For the image quality its important to choose the best fitting slice thickness for an examination. When a small item is entirely contained within the slice thickness with other tissue of differing signal intensity then the resulting signal displayed on the image is a combination of these two intensities. If the slice is the same thickness or thinner than the small structure, only that structures signal intensity is displayed on the image. This partial volume averaging effect explains the vanishing of fine details by choosing slices too large for the scanned object.
See also Partial Volume Artifact.
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Further Reading:
  Basics:
MRI Quality Control Program
   by www.simplyphysics.com    
  News & More:
Optimizing Musculoskeletal MR
   by rad.usuhs.mil    
Technical Assessment of Artifact Production from Neuro Endovascular Coil At 3 Tesla MRI: An In Vitro Study
2012   by www.tmps.or.th    
MRI Resources 
Stimulator pool - Shielding - IR - Fluorescence - Musculoskeletal and Joint MRI - Developers
 
ContrastForum -
related threads
 
Contrast is the relative difference of signal intensities in two adjacent regions of an image.
Due to the T1 and T2 relaxation properties in magnetic resonance imaging, differentiation between various tissues in the body is possible. Tissue contrast is affected by not only the T1 and T2 values of specific tissues, but also the differences in the magnetic field strength, temperature changes, and many other factors. Good tissue contrast relies on optimal selection of appropriate pulse sequences (spin echo, inversion recovery, gradient echo, turbo sequences and slice profile).
Important pulse sequence parameters are TR (repetition time), TE (time to echo or echo time), TI (time for inversion or inversion time) and flip angle. They are associated with such parameters as proton density and T1 or T2 relaxation times. The values of these parameters are influenced differently by different tissues and by healthy and diseased sections of the same tissue.
For the T1 weighting it is important to select a correct TR or TI. T2 weighted images depend on a correct choice of the TE. Tissues vary in their T1 and T2 times, which are manipulated in MRI by selection of TR, TI, and TE, respectively. Flip angles mainly affect the strength of the signal measured, but also affect the TR/TI/TE parameters.
Conditions necessary to produce different weighted images:
T1 Weighted Image: TR value equal or less than the tissue specific T1 time - TE value less than the tissue specific T2 time.
T2 Weighted Image: TR value much greater than the tissue specific T1 time - TE value greater or equal than the tissue specific T2 time.
Proton Density Weighted Image: TR value much greater than the tissue specific T1 time - TE value less than the tissue specific T2 time.
See also Image Contrast Characteristics, Contrast Reversal, Contrast Resolution, and Contrast to Noise Ratio.

 
Images, Movies, Sliders:
 Fetus (Brain) and Dermoid in Mother  Open this link in a new window
      

Courtesy of  Robert R. Edelman

 Circle of Willis, Time of Flight, MIP  Open this link in a new window
    
SlidersSliders Overview

 Anatomic MRI of the Knee 1  Open this link in a new window
    
SlidersSliders Overview

 Anatomic Imaging of the Liver  Open this link in a new window
      

 Brain MRI Inversion Recovery  Open this link in a new window
    
 
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• View the NEWS results for 'Contrast' (77).Open this link in a new window.
 
Further Reading:
  Basics:
Magnetic resonance imaging
   by www.scholarpedia.org    
MRI's inside story
Thursday, 4 December 2003   by www.economist.com    
Image Characteristics and Quality
   by www.sprawls.org    
  News & More:
Sharpening MRI Images
Sunday, 1 December 2013   by www.onlinetmd.com    
A natural boost for MRI scans
Monday, 21 October 2013   by www.eurekalert.org    
A groundbreaking new graphene-based MRI contrast agent
Friday, 8 June 2012   by www.nanowerk.com    
New MRI Chemical Offers Amazing Contrast
Friday, 22 January 2010   by news.softpedia.com    
Searchterm 'Slice Profile' was also found in the following service: 
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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 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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Further Reading:
  Basics:
MRI GLOSSARY
   by fonar.com    
Slice-overlap Artifacts
   by www.mritutor.org    
MRI Resources 
Veterinary MRI - Liver Imaging - Shielding - Open Directory Project - - Most Wanted
 
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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Further Reading:
  News & More:
MRI Artifact Gallery
   by chickscope.beckman.uiuc.edu    
MRI Resources 
Process Analysis - Nerve Stimulator - MRI Reimbursement - Supplies - Case Studies - Calculation
 
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