Dependence of Acquisition Trajectory on BOLD Sensitivity Changes Due to Magnetic Susceptibility Differences in the Brain

Thomas Le Paine^1,2, Brad P. Sutton^1,2

Magnetic susceptibility differences between air and tissues lead to magnetic field inhomogeneity in the brain that can cause artifacts during functional neuroimaging using the BOLD mechanism. When a gradient echo acquisition is used, gradients in the magnetic field inhomogeneity can cause effective echo time shifts that result in spatial variations in the sensitivity of BOLD. With a measured field map, these variations can be calculated and used to calibrate BOLD maps. We show BOLD maps from a breath hold task for four different acquisition trajectories on the same subject and compare them to the expected BOLD sensitivity maps.