Electron Spin Relaxation Time Measurements Using Radiofrequency Longitudinally Detected ESR and Application in Oximetry

Panagiotelis, Ioannis; Nicholson, Ian; Hutchison, J.M.S.

doi:10.1006/jmre.2000.2282

Cited by 14 publications

(19 citation statements)

References 47 publications

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“…119 The recent development of triarylmethyl radicals (Fig. 4) has significantly expanded the potential for using oxygen-sensitive free radicals in EPR, [156][157][158] EPR imaging 128,159,160 and related techniques such as dynamic nuclear polarization. [161][162][163] In human blood, the stability of triarylmethyl radicals varies from a half-life of a few hours to one of more than 24 h depending on the particular structure of the compound.…”

Section: Soluble Paramagnetic Materialsmentioning

confidence: 99%

Assessment of tumor oxygenation by electron paramagnetic resonance: principles and applications

2004

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This review paper attempts to provide an overview of the principles and techniques that are often termed electron paramagnetic resonance (EPR) oximetry. The paper discusses the potential of such methods and illustrates they have been successfully applied to measure oxygen tension, an essential parameter of the tumor microenvironment. To help the reader understand the motivation for carrying out these measurements, the importance of tumor hypoxia is first discussed: the basic issues of why a tumor is hypoxic, why these hypoxic microenvironments promote processes driving malignant progression and why hypoxia dramatically influences the response of tumors to cytotoxic treatments will be explained. The different methods that have been used to estimate the oxygenation in tumors will be reviewed. To introduce the basics of EPR oximetry, the specificity of in vivo EPR will be discussed by comparing this technique with NMR and MRI. The different types of paramagnetic oxygen sensors will be presented, as well as the methods for recording the information (EPR spectroscopy, EPR imaging, dynamic nuclear polarization). Several applications of EPR for characterizing tumor oxygenation will be illustrated, with a special emphasis on pharmacological interventions that modulate the tumor microenvironment. Finally, the challenges for transposing the method into the clinic will also be discussed.

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Section: Soluble Paramagnetic Materialsmentioning

confidence: 99%

Assessment of tumor oxygenation by electron paramagnetic resonance: principles and applications

2004

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“…The longitudinally detected ESR (LODESR) method was one of the techniques designed to observe ESR. In this technique, the signal is derived from a longitudinal oscillation of magnetization caused by spin flipping under on/off-modulated ESR irradiation, and is lock-in amplified by a detection frequency (11)(12)(13)(14)(15)(16). The longitudinal direction is parallel to the static magnetic field (B 0 ).…”

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confidence: 99%

“…Since this method reveals longitudinal magnetization (M z ) changes, it is suitable for determining the longitudinal relaxation time (T 1 ). It was previously reported that T 1 could be determined by investigating the LODESR signal intensity or phase as a function of frequency of on/off modulation of ESR irradiation (15,16). In this method, a pickup coil that efficiently detects the M z change must be tuned for multiple detection frequencies (equal to modulation frequencies).…”

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confidence: 99%

Noninvasive in vivo determination of intracerebral oxygen concentration in rats by a longitudinally detected ESR (LODESR) technique

Yokoyama

Sato

Fukui

et al. 2004

Magnetic Resonance in Med

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“…The spin‐lattice relaxation time of the electron, T 1 e , may or may not be dependent on agent concentration (23, 24) and can be obtained independently from inhomogeneous broadening effects by using LODESR (25, 26). The percentage change in T 1 e as a function of oxygen concentration is much greater than that of T 2 e in biological samples, in which the rotational correlation time of the spin probe increases due to increased viscosity and slow molecular dynamics of the local environment (19).…”

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confidence: 99%

“…T

_{*}^{1 italice}

and T

_{*}^{2 italice}

differ from the real T 1 e and T 2 e since they are not corrected for inhomogeneous broadening effects. T

_{*}^{1 italice}

and T

_{*}^{2 italice}

were determined by measuring the RF‐LODESR signal phase as a function of detection frequency, where phase is defined as the angle between the applied modulated excitation and the oscillation of the longitudinal magnetization ( M z ) (24). When T 1 e >> T 2 e , LODESR phase can give the real T 1 e and T 2 e , even for inhomogeneously broadened lines (25, 26).…”

mentioning

confidence: 99%

T and T maps derived in vivo from the rat using longitudinally detected electron spin resonance phase imaging: Application to abdominal oxygen mapping

Panagiotelis

Nicholson

Foster

et al. 2001

Magnetic Resonance in Med

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A novel imaging modality is introduced which uses radiofrequency longitudinally detected electron spin resonance (RF-LODESR). It is capable of providing qualitative and semiquantitative information on a variety of parameters reflecting physiological function, the most significant being tissue oxygenation. Effective spin-lattice (T * 1e ) and spin-spin (T * 2e ) electronic relaxation time maps of the abdomen of living 200-g rats were generated after intravenous administration of a triarylmethyl free radical (TAM). These maps were used to evaluate oxygen distribution. Differences between the liver, kidneys, and bladder were noted. Conclusions were made regarding the distribution, perfusion, and excretion rate of the contrast medium. Ligature-induced anoxia in the kidney was also visualized. LODESR involves transverse ESR irradiation with a modulated excitation, and observing oscillations in the spin magnetization parallel to the main magnetic field. The T * 1e and T * 2e maps were calculated from a set of LODESR signal phase images collected at different detection frequencies. Each phase image also provides qualitative information on tissue oxygen levels without any further processing. This method presents an alternative to the conventional transverse ESR linewidth-based oximetry methods, particularly for animal whole-body imaging applications. Magn

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Electron Spin Relaxation Time Measurements Using Radiofrequency Longitudinally Detected ESR and Application in Oximetry

Cited by 14 publications

References 47 publications

Assessment of tumor oxygenation by electron paramagnetic resonance: principles and applications

Assessment of tumor oxygenation by electron paramagnetic resonance: principles and applications

Noninvasive in vivo determination of intracerebral oxygen concentration in rats by a longitudinally detected ESR (LODESR) technique

T and T maps derived in vivo from the rat using longitudinally detected electron spin resonance phase imaging: Application to abdominal oxygen mapping

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