Jie Luo1, Xiang He2, Dmitriy A. Yablonskiy3, 4
1Chemistry, Washington University in St.Louis, St. Louis, MO, United States; 2University of Pittsburg; 3Radiology, Washington University in St.Louis; 4Physics, Washington University in St.Louis, United States
Phase images obtained by gradient echo MRI provide enhanced contrast of the brain anatomy. Possible origins of the phase/frequency contrast such as the magnetic susceptibility and the water-macromolecule exchange effects have been discussed. To describe the influence of tissue magnetic susceptibility on MR signal frequency shift, a proper relationship between these two values should be established. In this study, we have demonstrated that the Generalized Lorentzian Approach provides satisfactory explanation of the angular dependence of the phase contrast in longitudinal structures such as axons in white matter while usually assumed Lorentzian Sphere Approximation fails.