Abstract #3766
CORRECTION OF MACROSCOPIC FIELD INHOMOGENEITIES IN 3D QUANTITATIVE GRE IMAGING BASED ON NONLINEAR PHASE MODEL AND SNR MAPPING
Chemseddine Fatnassi 1,2 , Rachid Boucenna 1 , Michael Betz 1 , and Habib Zaidi 3
1
Radio-oncology, Hirslanden Lausanne,
Lausanne, vaud, Switzerland,
2
Faculty
of biology and Medicine, UNIL, Lausanne, vaud,
Switzerland,
3
Division
of Nuclear Medicine and Molecular Imaging, Geneva
University Hospital, Geneva, Switzerland
In 3D gradient echo (GRE) imaging, strong macroscopic B0
field gradients (Gr) are observed at air/tissue
interfaces and in the presence of metallic objects. In
particular, at low spatial resolution, the respective
field gradients lead to an apparent increase in the
intra-voxel dephasing and subsequently to signal loss or
inaccurate R2* estimates. If the macroscopic gradient
through a voxel (Gr) can be estimated, its influence can
be removed through post-processing. The proposed
correction strategies usually assume a linear phase
evolution with time. However, near the edge of the
brain, the paranasal sinus and temporal lobes, this
assumption is often broken. In this work, we explore a
model that considers a non-linear dependence of the
phase evolution with echo time. The correction model is
then weighted by the SNR map computed from the magnitude
image in order to remove singularities caused by
inaccurate field map estimation. We tested the
performance of the proposed model for correcting of
artifacts in a physical phantom with different MnCl2
concentrations and in vivo clinical studies.
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