Theoretical and experimental evaluation of phase-dispersion effects caused by brain motion in diffusion and perfusion MR imaging

Ronnie Wirestam*, Dan Greitz, Carsten Thomsen, Sara Brockstedt, Magnus B.E. Olsson, Freddy Ståhlberg

*Corresponding author af dette arbejde

    Publikation: Bidrag til tidsskriftArtikelForskningpeer review

    Abstract

    We investigated intravoxel phase dispersion caused by pulsatile brain motion in diffusion spin-echo pulse sequences. Mathematical models were used to describe the spatial and temporal velocity distributions of human brain motion. The spatial distribution of brain-tissue velocity introduces a phase spread over one voxel, leading to signal loss. This signal loss was estimated theoretically, and effects on observed diffusion coefficient and perfused capillary fraction were assessed. When parameters from a diffusion pulse sequence without motion compensation were used, and ECG triggering with inappropriate delay times was assumed, the maximal signal loss caused by brain-motion-induced phase dispersion was predicted to be 21%. This corresponds to a 95% overestimation of the diffusion coefficient, and the perfusion-fraction error was small. Corresponding calculations for motion-compensated pulse sequences predicted a 1% to 1.5% signal loss due to undesired phase dispersion, whereas experimental results indicated a signal loss related to brain motion of 4%.

    OriginalsprogEngelsk
    Sider (fra-til)348-355
    Antal sider8
    TidsskriftJournal of Magnetic Resonance Imaging
    Vol/bind6
    Udgave nummer2
    DOI
    StatusUdgivet - 1 jan. 1996

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