Electron spin relaxation time measurements using radiofrequency longitudinally detected ESR and application in oximetry

I. Panagiotelis, I. Nicholson, James McDonald Strachan Hutchison

    Research output: Contribution to journalArticle

    12 Citations (Scopus)

    Abstract

    Longitudinally detected ESR (LODESR) involves transverse ESR irradiation with a modulated source and observing oscillations in the spin magnetization parallel to the main magnetic field. In this study, radiofrequency-LODESR was used for oximetry by measuring the relaxation times of the electron. T-1e, and T-2e were measured by investigating LODESR signal magnitude as a function of detection frequency. We have also predicted theoretically and verified experimentally the LODESR signal phase dependence on detection frequency and relaxation times. These methods are valid even for inhomogeneous lines provided that T-1e much greater than T-2e. We have also developed a new method for measuring T-1e valid for inhomogeneous spectra, for all values of T-1e and T-2e, based on measuring the spectral area as a function of detection frequency. We have measured T-1e and T-2e for lithium phthalocyanine crystals, for the nitroxide TEMPOL, and for the single line agent Triarylmethyl (TAM). Furthermore, we have collected spectra from aqueous solutions of TEMPOL and TAM at different oxygen concentrations and confirmed that T-1e values are reduced with increased oxygen concentration. We have also measured the spin-lattice electronic relaxation time for degassed aqueous solutions of the same agents at different agent concentrations. T-1e decreases as a function of concentration for TAM while it remains independent of free radical concentration for TEMPOL, a major advantage for oxygen mapping. This method, combined with the ability of LODESR to provide images of exogenous free radicals in vivo, presents an attractive alternative to the conventional transverse ESR linewidth based oximetry methods. (C) 2001 Academic Press.

    Original languageEnglish
    Pages (from-to)74-84
    Number of pages10
    JournalJournal of Magnetic Resonance
    Volume149
    Issue number1
    DOIs
    Publication statusPublished - 2001

    Keywords

    • LODESR
    • oximetry
    • electron relaxation times
    • in vivo EPR
    • inhomogeneous broadening
    • PARAMAGNETIC-RESONANCE
    • LATTICE RELAXATION
    • LITHIUM PHTHALOCYANINE
    • CONTINUOUS-WAVE
    • EPR
    • OXYGEN
    • RECOVERY
    • LABELS
    • PROBE
    • RATS

    Cite this

    Electron spin relaxation time measurements using radiofrequency longitudinally detected ESR and application in oximetry. / Panagiotelis, I.; Nicholson, I.; Hutchison, James McDonald Strachan.

    In: Journal of Magnetic Resonance, Vol. 149, No. 1, 2001, p. 74-84.

    Research output: Contribution to journalArticle

    Panagiotelis, I. ; Nicholson, I. ; Hutchison, James McDonald Strachan. / Electron spin relaxation time measurements using radiofrequency longitudinally detected ESR and application in oximetry. In: Journal of Magnetic Resonance. 2001 ; Vol. 149, No. 1. pp. 74-84.
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    AU - Panagiotelis, I.

    AU - Nicholson, I.

    AU - Hutchison, James McDonald Strachan

    PY - 2001

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    N2 - Longitudinally detected ESR (LODESR) involves transverse ESR irradiation with a modulated source and observing oscillations in the spin magnetization parallel to the main magnetic field. In this study, radiofrequency-LODESR was used for oximetry by measuring the relaxation times of the electron. T-1e, and T-2e were measured by investigating LODESR signal magnitude as a function of detection frequency. We have also predicted theoretically and verified experimentally the LODESR signal phase dependence on detection frequency and relaxation times. These methods are valid even for inhomogeneous lines provided that T-1e much greater than T-2e. We have also developed a new method for measuring T-1e valid for inhomogeneous spectra, for all values of T-1e and T-2e, based on measuring the spectral area as a function of detection frequency. We have measured T-1e and T-2e for lithium phthalocyanine crystals, for the nitroxide TEMPOL, and for the single line agent Triarylmethyl (TAM). Furthermore, we have collected spectra from aqueous solutions of TEMPOL and TAM at different oxygen concentrations and confirmed that T-1e values are reduced with increased oxygen concentration. We have also measured the spin-lattice electronic relaxation time for degassed aqueous solutions of the same agents at different agent concentrations. T-1e decreases as a function of concentration for TAM while it remains independent of free radical concentration for TEMPOL, a major advantage for oxygen mapping. This method, combined with the ability of LODESR to provide images of exogenous free radicals in vivo, presents an attractive alternative to the conventional transverse ESR linewidth based oximetry methods. (C) 2001 Academic Press.

    AB - Longitudinally detected ESR (LODESR) involves transverse ESR irradiation with a modulated source and observing oscillations in the spin magnetization parallel to the main magnetic field. In this study, radiofrequency-LODESR was used for oximetry by measuring the relaxation times of the electron. T-1e, and T-2e were measured by investigating LODESR signal magnitude as a function of detection frequency. We have also predicted theoretically and verified experimentally the LODESR signal phase dependence on detection frequency and relaxation times. These methods are valid even for inhomogeneous lines provided that T-1e much greater than T-2e. We have also developed a new method for measuring T-1e valid for inhomogeneous spectra, for all values of T-1e and T-2e, based on measuring the spectral area as a function of detection frequency. We have measured T-1e and T-2e for lithium phthalocyanine crystals, for the nitroxide TEMPOL, and for the single line agent Triarylmethyl (TAM). Furthermore, we have collected spectra from aqueous solutions of TEMPOL and TAM at different oxygen concentrations and confirmed that T-1e values are reduced with increased oxygen concentration. We have also measured the spin-lattice electronic relaxation time for degassed aqueous solutions of the same agents at different agent concentrations. T-1e decreases as a function of concentration for TAM while it remains independent of free radical concentration for TEMPOL, a major advantage for oxygen mapping. This method, combined with the ability of LODESR to provide images of exogenous free radicals in vivo, presents an attractive alternative to the conventional transverse ESR linewidth based oximetry methods. (C) 2001 Academic Press.

    KW - LODESR

    KW - oximetry

    KW - electron relaxation times

    KW - in vivo EPR

    KW - inhomogeneous broadening

    KW - PARAMAGNETIC-RESONANCE

    KW - LATTICE RELAXATION

    KW - LITHIUM PHTHALOCYANINE

    KW - CONTINUOUS-WAVE

    KW - EPR

    KW - OXYGEN

    KW - RECOVERY

    KW - LABELS

    KW - PROBE

    KW - RATS

    U2 - 10.1006/jmre.2000.2282

    DO - 10.1006/jmre.2000.2282

    M3 - Article

    VL - 149

    SP - 74

    EP - 84

    JO - Journal of Magnetic Resonance

    JF - Journal of Magnetic Resonance

    SN - 1090-7807

    IS - 1

    ER -