Field-cycled PEDRI imaging of free radicals with detection at 450 mT

David John Lurie* (Corresponding Author), Gareth Reynold Davies, M. A. Foster, James McDonald Strachan Hutchison

*Corresponding author for this work

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This paper describes the design, construction and use of a field-cycled proton–electron double-resonance imaging (FC-PEDRI) system for the detection and imaging of free radicals. The unique feature of this imager is its use of a 450-mT detection magnetic field in order to achieve good image quality and sensitivity. The detection magnetic field is provided by a superconducting magnet, giving high stability and homogeneity. Field cycling is implemented by switching on and off the current in an internal, coaxial, resistive secondary magnet that partially cancels the superconducting magnet's field at the sample; the secondary magnet is actively shielded to avoid eddy currents. EPR irradiation takes place at ∼5 mT, following which the field is switched to 450 mT in 40 ms for NMR signal detection. Full details of the imager's subsystems are given, and experiments to image the distribution of stable free radical contrast agents in phantoms and in anesthetized rats are described.

Original languageEnglish
Pages (from-to)175-181
Number of pages6
JournalMagnetic Resonance Imaging
Issue number2
Publication statusPublished - Feb 2005

Bibliographical note

Funding was provided by the Engineering and Physical Sciences Research Council under grant number GR/M46488/01 and by the University of Aberdeen. The authors thank Mr. Takuya Yokoyama for writing software to facilitate subtraction of complex data sets, Mr. Eddie Stevenson for help with the mechanical construction of the FC-PEDRI system and Dr. Klaes Golman of Nycomed-Amersham for the kind gift of TAM radical.


  • field-cycling
  • Overhauser imaging
  • free radical


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