The "Central Signal Singularity" Phenomenon in Balanced SSFP

R. Reeve Ingle¹, Dwight G. Nishimura¹

We investigate a phenomenon whereby small, alternating perturbations of parameters (such as RF flip angles or phases) in a balanced SSFP sequence can cause large, localized deviations in the steady-state magnetization profile. These deviations can be very severe (e.g., sharp notches or spikes in the magnetization profile) but localized to a narrow range of off-resonant frequencies, with the rest of the profile being essentially identical to the unperturbed bSSFP profile. We develop mathematical and physical explanations of this phenomenon, demonstrate via Bloch simulations, present phantom results, and describe potential applications for positive-contrast imaging and fMRI.