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Susceptibility gradient quantization by MRI signal response mapping (SIRMA) to dephaser.
F Franconi1, C Chapon, J J Le Jeune
1Plateforme d'Ingénierie et d'Analyses Moléculaires, Université d'Angers, 45045 Angers, France. florence.franconi@univ-angers.fr
Medical Physics
|March 17, 2010
Summary
The novel SIgnal Response MApping (SIRMA) method visualizes magnetic susceptibility gradients in MRI by mapping k-space shifts. This technique accurately delineates SPIO-loaded nanocapsule distribution in vivo, offering quantitative potential for molecular imaging.
Area of Science:
- Medical Imaging
- Biophysics
- Nanotechnology
Background:
- Magnetic resonance imaging (MRI) contrast is often limited by negative susceptibility effects.
- Detecting these susceptibility effects is challenging due to inherent signal loss.
Purpose of the Study:
- To introduce the SIgnal Response MApping (SIRMA) method for improved visualization of susceptibility gradients.
- To map susceptibility gradients by measuring induced k-space shifts in MRI.
Main Methods:
- SIRMA measures k-space shifts caused by susceptibility gradients using a series of dephased images with incremental dephasers.
- Pixel-by-pixel analysis of signal intensity profiles determines shift magnitude and sign to generate susceptibility gradient maps.
Main Results:
- In vitro experiments successfully mapped gradient inhomogeneities and demonstrated quantization accuracy.
- In vivo studies in rat brains clearly delineated SPIO-loaded nanocapsule distribution, showing quantitative potential.
- SIRMA maps were compared favorably to T2* weighted images, Susceptibility Gradient Maps (SGM), and histology.
Conclusions:
- The SIRMA method is a promising, computationally simple technique for quantitative susceptibility mapping.
- Its quantitative nature makes it particularly suitable for molecular and cellular imaging applications.
