Examination of susceptibility effects on functional and dynamic magnetic resonance imaging
A homogeneous, static magnetic field is important in magnetic resonance imaging. When a homogeneous field is not present it can cause imaging artifacts and misestimation of tissue structures, flow, and brain function. However, magnetic field inhomogeneity also drives certain contrast mechanisms including blood oxygenation level dependent fMRI. The two projects in this work look at the effects of inhomogeneity on functional and dynamic MRI. We simultaneously acquired functional and dynamic MRI (Simulscan) of natural un-cued swallows. Work was done to minimize susceptibility artifacts in the dynamic images, but still have susceptibility induced BOLD contrast in functional MRI, but some residual susceptibility issues remained. We analyzed these residual susceptibility issues in BOLD, and develop a calibration procedure to remove these effects. This work focuses in-plane gradients of the magnetic field that result in spatially-varying BOLD sensitivity. These artifacts depend on subject-specific magnetic-field distributions in the brain as well as acquisition. To correct these spatially-varying BOLD-sensitivity artifacts, a calibration for percent-signal-change measures is developed.
Magnetic Resonance Imaging (MRI), Functional Magnetic Resonance Imaging (fMRI), magnetic susceptibility, Dynamic Magnetic Resonance Imaging (MRI), Simulscan
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign