Pulse-wave velocity measured in one heartbeat using MR tagging.
A noninvasive method for measuring the aortic pulse-wave velocity (PWV) in a single heartbeat is introduced. The method sinusoidally tags a column of blood within the vessel, and rapidly acquires a series of 1D projections of the tags as they move (in practice, 64 projections at 4-ms intervals). From these projections, the relative motion of blood at different positions along the vessel is measured. The PWV is obtained by fitting a mathematical model of blood flow to the tag trajectories. Tests of this method in a pulsatile flow phantom are presented using latex and polyurethane tubes. The PWV measured in these tubes was (mean +/- standard deviation) 4.4 +/- 0.5 m/s and 2.3 +/- 0.2 m/s, respectively. The distensibility of each tube was calculated from the PWV (latex = (7 +/- 2) 10(-3) mm Hg(-1), poly. = (25 +/- 4) 10(-3)mmHg(-1)) and found to agree within error with distensibility measurements based on the change of tube area with pressure (latex = (6.3 +/- 0.3) 10(-3)mmHg(-1), poly. = (27 +/- 1) 10(-3) mmHg(-1)). To test its feasibility, the PWV measurement was applied to four normal volunteers. The measured PWV values were 3.9 +/- 0.8 m/s, 3.6 +/- 0.9 m/s, 3.9 +/- 0.5 m/s, and 5.3 +/- 0.8 m/s. By acquiring an independent PWV measurement each heartbeat, errors introduced by arrhythmia and trigger variability appear to be avoided with this method.
Department of Diagnostic Imaging, The Hospital for Sick Children, The University of Toronto, Ontario, Canada. chris.macgowen@utoronto.ca
Christopher K
CK
Macgowan
R Mark
RM
Henkelman
Michael L
ML
Wood
D001011:Aorta / Q000502:physiology; D001783:Blood Flow Velocity; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008433:Mathematics; D008962:Models, Theoretical; D011673:Pulsatile Flow; D011674:Pulse