Optimal bipolar gradient design to reduce velocity offsets

Introduction: Phase-contrast velocity quantification is a valuable tool in cardiac magnetic resonance imaging. However, eddy-currents cause additional signal phases, which result in offsets in the velocity measurements. Even a relative small offset (>0.6 cm/s) can result in significant errors in clinical parameters [1]. Gatehouse et al. [2] showed that for a typical breath-hold flow protocol none of several commercial MR scanners had sufficiently small offsets for reliable accuracy in cardiac volume flow measurements. Optimal sequence design by slowing down the sequence, by timing or gradients, might reduce the offsets due to eddy currents [3]. Furthermore, the effect of asymmetric versus symmetric velocity encoding is largely unknown. With an adapted sequence these concepts were tested in a setting comparable to a clinical set-up.