RANZCR ASM 2011 / R-0186
Susceptibility Weighted Imaging
This poster was originally presented at the RANZCR Annual Scientific Meeting 2011, October 6-9, in Melbourne/AU.
Congress:
RANZCR ASM 2011
Keywords:
Neuroradiology brain, MR, Imaging sequences
Authors:
S. Bhuta; Gold Coast/AU
DOI:
10.1594/ranzcr2011/R-0186
Main
Typical MRI sequences utilize magnitude data to produce tissue
contrast.
In SWI,
a gradient echo sequence is utilized with TR
and TE values set to produce an image somewhere between T1
and T2 weighting.
The magnitude image is produced as in any
normal MRI sequence.
Phase data have historically been discarded
as any useful information was obscured by background
magnetic field inhomogeneity.
Development of sophisticated
phase filters has enabled removal of unwanted phase artefacts
producing useful soft tissue contrast and a usable image.
Multiplying
the phase and magnitude data sets produces the final
SWI image used for diagnostic purposes.
This process is performed
automatically by the MRI console and is presented as a
Minimum Intensity Projection (MNIP).
This MNIP can then be
processed to produce a more conventional axial image correlating
to 4-mm Slice thickness.
The combination of magnitude
and phase information provides the exquisite sensitivity for susceptibility effect.
Display of the phase image is also required to
allow complete interpretation of the sequence.Phase images can be utilised to differentiate calcium from blood products,
something which is not possible on conventional T2 * sequence