title: Extrinsic multiecho phase-contrast SSFP: evaluation on cardiac output measurements.
abstract: Multiecho phase-contrast steady-state free precession (PC-SSFP) is a recently introduced sequence for flow quantification. In this multiecho approach, a phase reference and a velocity-encoded readout were acquired at different echo times after a single excitation. In this study, the sequence is validated in vitro for stationary flow. Subsequently, the sequence was evaluated on cardiac output measurements in vivo for through-plane flow in comparison to regular single gradient echo velocity quantification [phase-contrast spoiled gradient echo (PC-GE)]. In vitro results agreed with regular flow meters (RMS 0.1 cm/s). Cardiac output measurements with multiecho PC-SSFP on 10 healthy subjects gave on average the same results as the standard PC-GE. However, the limits of repeatability of PC-SSFP were significantly larger than those of PC-GE (2 l/min and 0.5 l/min, respectively, P=.001). The multiecho approach introduced some specific problems in vivo. The difference in echo times made the velocity maps sensitive for water-fat shifts and B(0)-drifts, which in turn made velocity offset correction problematic. Also, the addition of a single bipolar gradient cancelled the flow compensated nature of the SSFP sequence. In combination with the prolonged TR, this resulted in flow artifacts caused by high and pulsatile through-plane flow, affecting repeatability. Given the significantly lower repeatability of PC-SSFP, cardiac output in turn is less reliable, thus impairing the use of multiecho PC-SSFP.
authors.affiliation: Department of Physics and Medical Technology, ICaR-VU, VU University Medical Center, 1007 MB Amsterdam, The Netherlands. mp.rolf@vumc.nl
authors.forename: Marijn P
authors.initials: MP
authors.lastname: Rolf
authors.forename: Mark B M
authors.initials: MB
authors.lastname: Hofman
authors.forename: Joost P A
authors.initials: JP
authors.lastname: Kuijer
authors.forename: Vinay M
authors.initials: VM
authors.lastname: Pai
authors.forename: Andreas
authors.initials: A
authors.lastname: Greiser
authors.forename: Albert C
authors.initials: AC
authors.lastname: van Rossum
authors.forename: Rob M
authors.initials: RM
authors.lastname: Heethaar