Macroscopic background gradient and radiation damping effects on high-field PGSE NMR diffusion measurements

William S. Price, Peter Stilbs, B. Jonsson, O. Soderman

    Research output: Contribution to journalArticle

    47 Citations (Scopus)

    Abstract

    The effects of macroscopic background gradients due to susceptibility differences at the sample interfaces and of radiation damping on pulsed-gradient spin-echo (PGSE) experiments are examined. Both phenomena can lead to the seemingly strange effect of the echo signal growing as the gradient strength increases at low applied gradient strengths. For a freely diffusing species, background gradients manifest themselves as slight concave or convex inflections in the linearized PGSE attenuation curve, depending on the polarity of the applied gradient. The various means of overcoming macroscopic background gradient problems, including bipolar gradients, and their efficacy are examined experimentally and discussed. The effects of radiation damping can also result in the attenuation curve being nonlinear but, different from the effect of background gradients, the nonlinearity does not change with the polarity of the applied gradient. The vulnerability of the stimulated echo-based PGSE sequence and variations of Hahn-based PGSE sequences is investigated. Both background gradients and radiation damping have serious implications for accurate diffusion measurement determination.
    Original languageEnglish
    Pages (from-to)49-56
    Number of pages8
    JournalJournal of Magnetic Resonance
    Volume150
    Issue number1
    Publication statusPublished - 2001

    Keywords

    • PGSE
    • background gradients
    • bipolar gradients
    • calibration
    • diffusion
    • radiation damping

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