Abstract
Dynamic nuclear polarization (DNP) is an NMR-based technique which enables detection and spectral characterization of endogenous and exogenous paramagnetic substances measured via transfer of polarization from the saturated unpaired electron spin system to the NMR active nuclei. A variable field system capable of performing DNP spectroscopy with NMR detection at any magnetic field in the range 0-0.38T is described. The system is built around a clinical open-MRI system. To obtain EPR spectra via DNP, partial cancellation of the detection field B(0)(NMR) is required to alter the evolution field B(0)(EPR) at which the EPR excitation is achieved. The addition of resistive actively shielded field cancellation coils in the gap of the primary magnet provides this field offset in the range of 0-100mT. A description of the primary magnet, cancellation coils, power supplies, interfacing hardware, RF electronics and console are included. Performance of the instrument has been evaluated by acquiring DNP spectra of phantoms with aqueous nitroxide solutions (TEMPOL) at three NMR detection fields of 97G, 200G and 587G corresponding to 413kHz, 851.6kHz and 2.5MHz respectively and fixed EPR evolution field of 100G corresponding to an irradiation frequency of 282.3MHz. This variable-field DNP system offers great flexibility for the performance of DNP spectroscopy with independent optimum choice of EPR excitation and NMR detection fields.
Original language | English |
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Pages (from-to) | 202-208 |
Number of pages | 7 |
Journal | Journal of Magnetic Resonance |
Volume | 205 |
Issue number | 2 |
Early online date | 31 May 2010 |
DOIs | |
Publication status | Published - Aug 2010 |
Keywords
- proton MRI
- EPR imaging
- free radicals
- oxygen
- image co-registration
- in vivo NMR
- in vivo EPR
- Overhauser effect