title: Real-time phase-contrast MRI of cardiovascular blood flow using undersampled radial fast low-angle shot and nonlinear inverse reconstruction.
abstract: Velocity-encoded phase-contrast MRI of cardiovascular blood flow commonly relies on electrocardiogram-synchronized cine acquisitions of multiple heartbeats to quantitatively determine the flow of an averaged cardiac cycle. Here, we present a new method for real-time phase-contrast MRI that combines flow-encoding gradients with highly undersampled radial fast low-angle shot acquisitions and phase-sensitive image reconstructions by regularized nonlinear inversion. Apart from calibration studies using steady and pulsatile flow, preliminary in vivo applications focused on through-plane flow in the ascending aorta of healthy subjects. With bipolar velocity-encoding gradients of alternating polarity that overlap the slice-refocusing gradient, the method yields flow-encoded images with an in-plane resolution of 1.8 mm, section thickness of 6 mm and measuring time at 3 T of 24 ms (TR/TE = 3.44/2.76 ms; flip angle, 10º; seven radial spokes per image). Accordingly, phase-contrast maps and corresponding velocity profiles achieve a temporal resolution of 48 ms. The evaluated peak velocities, stroke volumes, flow rates and respective variances over at least 20 consecutive heartbeats are in general agreement with literature data.
authors.affiliation: Biomedizinische NMR Forschungs GmbH am Max-Planck-Institut für biophysikalische Chemie, Göttingen, Germany. jfrahm@gwdg.de
authors.forename: Arun A
authors.initials: AA
authors.lastname: Joseph
authors.forename: Klaus-Dietmar
authors.initials: KD
authors.lastname: Merboldt
authors.forename: Dirk
authors.initials: D
authors.lastname: Voit
authors.forename: Shuo
authors.initials: S
authors.lastname: Zhang
authors.forename: Martin
authors.initials: M
authors.lastname: Uecker
authors.forename: Joachim
authors.initials: J
authors.lastname: Lotz
authors.forename: Jens
authors.initials: J
authors.lastname: Frahm
mesh_terms: D000293:Adolescent; D000328:Adult; D001011:Aorta / Q000502:physiology; D001783:Blood Flow Velocity / Q000502:physiology*; D003326:Coronary Circulation / Q000502:physiology; D006321:Heart / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods; D008297:Male; D008875:Middle Aged; D011673:Pulsatile Flow / Q000502:physiology; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D013318:Stroke Volume / Q000502:physiology