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Triarylmethyl Radical OX063d24 Oximetry: Electron Spin Relaxation at 250 MHz and RF Frequency Dependence of Relaxation and Signal-to-Noise

  • Yilin Shi
  • Richard W. Quine
  • George A. Rinard
  • Laura Buchanan
  • Sandra S. Eaton
  • Gareth R. EatonEmail author
  • Boris Epel
  • Simone Wanless Seagle
  • Howard J. Halpern
Chapter
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 977)

Abstract

The triarylmethyl radical OX063d24 is currently used for pulsed electron paramagnetic resonance oximetry at 250 MHz. Both 1/T1 and 1/T2 increase with increasing oxygen concentration. The dependence of 1/T1 on probe concentration is smaller than for 1/T2. To inform the selection of the optimum frequency for in vivo oximetry 1/T1, 1/T2 and signal-to-noise were measured as a function of frequency between 400 and 1000 MHz on a variable-frequency spectrometer with an adjustable-frequency cross-loop resonator. 1/T1 and 1/T2 decrease with increasing frequency and signal-to-noise increases with increasing frequency, which are all favourable for imaging at higher frequencies. However, depth of penetration of the radio frequency (RF) into an animal decreases with increasing frequency. Assuming that the RF loss in the animal to be studied determines the resonator Q, our results indicate that the optimum frequency for in vivo imaging will be determined by the desired depth of penetration in the tissue.

Keywords

Electron spin relaxation Oximetry Signal-to-noise ratio Variable frequency Triarylmethyl radical 

Notes

Acknowledgments

This research was funded in part by NIH P41 EB002034 (HJH, PI), R01 CA098575 (HJH, PI) and R01CA177744 (GRE, PI).

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Copyright information

© Springer International Publishing AG 2017

Authors and Affiliations

  • Yilin Shi
    • 1
  • Richard W. Quine
    • 2
  • George A. Rinard
    • 2
  • Laura Buchanan
    • 1
  • Sandra S. Eaton
    • 1
  • Gareth R. Eaton
    • 1
    Email author
  • Boris Epel
    • 3
  • Simone Wanless Seagle
    • 3
  • Howard J. Halpern
    • 3
  1. 1.Department of Chemistry and Biochemistry and Center for EPR Imaging In Vivo PhysiologyUniversity of DenverDenverUSA
  2. 2.School of Engineering and Computer Science and Center for EPR Imaging In Vivo PhysiologyUniversity of DenverDenverUSA
  3. 3.Department of Radiation and Cellular Oncology and Center for EPR Imaging In Vivo PhysiologyUniversity of ChicagoChicagoUSA

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