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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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