Nontriggered Cartesian steady-state free precession phase-contrast MR

Introduction: Nontriggered phase-contrast (PC)-MR has been proposed for measurement of time-averaged velocity [1]. However, gradient-echo PC-MR is biased by in-flow enhancement when typical flip angles and slice widths are used, leading to velocity overestimation [2]. We hypothesize that nontriggered PCsteady state free precession (SSFP), which exhibits less signal variation over the cardiac cycle [3], will provide a more accurate mean-velocity measurement than conventional nontriggered PC-MR. This will be important for applications lacking a cardiac gating signal, such as fetal-flow measurement.