Short-echo-time magnetic resonance phase-shift velocity mapping for assessment of heart valve and great vessel stenoses: three years' experience

Abstract

Shortening the echo times of magnetic resonance (MR) sequences used for phase-shift velocity mapping to 3.6 ms has extended use of the technique to measurement of velocities in turbulent, poststenotic jet flows. We used a 0.5-T MR machine and field even-echo rephasing (FEER) sequences with 3.6 ms echo times for jet velocity mapping.In vitro trials used continuous flow through a phantom with a 6-mm stenosis. Fifteen patients with mitral and/or aortic valve stenosis and 20 patients with repaired aortic coarctation were studied prospectively, with Doppler ultrasonic measurement of peak jet velocity performed independently on the same day. The clinical contribution of MR jet velocity mapping, used during a 3-year period in 306 patients with congenital and acquired disease of heart valves, great vessels, and conduits, was assessed retrospectively. The 3.6-ms sequence allowed accurate measurement of jet velocities up to 6 m s⁻¹ in vitro (r=0.996). Prospective studies in patients showed good agreement between MR and Doppler measurements of peak velocity:n=38; range, 1.2–6.1 m s⁻¹; mean, 2.7 m s⁻¹; mean of differences (Doppler-MR), 0.22 ms⁻¹; standard deviation of differences, ±0.38 m s⁻¹ (±14%). MR jet velocity mapping proved particularly valuable for assessment and localization of stenoses at sites where ultrasonic access was limited. The technique represents a diagnostic advance which can obviate the need for catheterization in selected cases.