title: Improving the robustness of pseudo-continuous arterial spin labeling to off-resonance and pulsatile flow velocity.
abstract: To improve pseudo-continuous arterial spin labeling (PCASL) robustness to off-resonance and pulsatile blood flow velocity.
  
  
  
  Bloch equations were solved to evaluate the effect of labeling parameters in a pulsatile flow model for a range of off-resonance. Experimental confirmation was achieved in volunteers using linear phase increase between labeling pulses to approximate off-resonance errors. We first assessed the location of the labeling plane in four volunteers. Next, we explored a range of parameters-including balanced and unbalanced gradients-in five more volunteers at an optimal labeling plane location.
  
  
  
  Simulations demonstrated that 1) high velocities are vulnerable to off-resonance, 2) unbalanced PCASL outperforms balanced PCASL, 3) increased B1 and low average gradient improve the labeling efficiency for high-velocity flow, and 4) a low ratio of selective to average gradient improves off-resonance robustness. A good agreement between theory and experiment was observed.
  
  
  
  The robustness of PCASL can be increased by selecting an unbalanced scheme with a low average gradient (0.5 mT/m), a low ratio (7×) of selective to average gradients, and the highest feasible B1 (1.8 μT). Placing the labeling plane above the carotid bifurcation and below the V3 segment, usually between the second and third vertebrae, yielded robust results. Magn Reson Med 78:1342-1351, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
authors: Department of Radiology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA.
authors: Li
authors: 0000-0003-4933-3183
authors: L
authors: Zhao
authors: Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.|Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors: Marta
authors: M
authors: Vidorreta
authors: Department of Radiology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA.
authors: Salil
authors: S
authors: Soman
authors: Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.|Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors: John A
authors: JA
authors: Detre
authors: Department of Radiology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA.
authors: David C
authors: DC
authors: Alsop
mesh_terms: D000328:Adult; D001921:Brain / Q000098:blood supply / Q000000981:diagnostic imaging; D003198:Computer Simulation; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods*
keywords: balanced PCASL; labeling efficiency; off-resonance; pseudo-continuous arterial spin labeling (PCASL); unbalanced PCASL