B0 field inhomogeneity considerations in pseudo-continuous arterial spin labeling (pCASL): effects on tagging efficiency and correction strategy

Authors

  • Hesamoddin Jahanian,

    Corresponding author
    1. Functional MRI Laboratory, University of Michigan, Ann Arbor, MI, USA
    2. Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
    • Functional MRI Laboratory, University of Michigan, 2360 Bonisteel Ave., Ann Arbor, MI 48109-2108, USA.

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  • Douglas C. Noll,

    1. Functional MRI Laboratory, University of Michigan, Ann Arbor, MI, USA
    2. Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
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  • Luis Hernandez-Garcia

    1. Functional MRI Laboratory, University of Michigan, Ann Arbor, MI, USA
    2. Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
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Abstract

Pseudo-continuous arterial spin labeling (pCASL) is a very powerful technique to measure cerebral perfusion, which circumvents the problems affecting other continuous arterial spin labeling schemes, such as magnetization transfer and duty cycle. However, some variability in the tagging efficiency of the pCASL technique has been reported. This article investigates the effect of B0 field inhomogeneity on the tagging efficiency of the pCASL pulse sequence as a possible cause of this variability. Both theory and simulated data predict that the efficiency of pseudo-continuous labeling pulses can be degraded in the presence of off-resonance effects. These findings are corroborated by human in vivo measurements of tagging efficiency. On the basis of this theoretical framework, a method utilizing B0 field map information is proposed to correct for the possible loss in tagging efficiency of the pCASL pulse sequence. The efficiency of the proposed correction method is evaluated using numerical simulations and in vivo implementation. The data show that the proposed method can effectively recover the lost tagging efficiency and signal-to-noise ratio of pCASL caused by off-resonance effects. Copyright © 2011 John Wiley & Sons, Ltd.

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