Balanced SSFP Profile Asymmetries Detect Small Frequency Shifts in White Matter

Karla L. Miller¹, Peter Jezzard¹

We study a novel contrast mechanism based on the frequency dependence of the balanced SSFP signal. The balanced SSFP profile is theoretically symmetric with respect to frequency if only T₁, T₂ and diffusion effects are considered. However, the convolution model for the SSFP signal predicts that the profile becomes asymmetric for asymmetric lineshapes. Asymmetries are observed in white matter. The model is fit to data using a simple lineshape parameterization, and data is shown to be consistent with lineshape effects at small frequency offsets. SSFP asymmetries may be a sensitive marker of tissue microstructure, as reflected by small frequency shifts.