Technical note: a moderately sized resonator/surface coil for radiofrequency electron paramagnetic resonance spectroscopy and imaging in vivo.
A resonator for the radiofrequency (250 MHz) electron paramagnetic resonance spectroscopy (EPRS) and imaging (EPRI) of biological samples is described. It has been designed for use with a 0.5 m bore EPR spectrometer. It is of the double split-ring type, 65 mm in diameter and 100 mm in length, and is equipped with a tuning-lock mechanism for fixed frequency operation. It can be used in the whole-body mode for small animals and as a surface coil for larger samples. The extent of sensitivity in the latter mode is ca. 20 mm. Larger resonators are being developed for whole-body human studies. A phase-locked crystal oscillator frequency source with high spectral purity is used to minimize noise demodulation and automatic tuning; coupling and phase controls have been included to compensate for motional artefacts. For purely aqueous nitroxides, the minimum detectable concentration is ca. 4 x 10(-7) M using an internal sample 100 ml in volume. Sensitivity in the surface coil mode is discussed and spectra from phantoms using both physiological saline and a human volunteer to induce realistic conduction losses are shown.
Stevens
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AD
Department of Radiology, University of Leicester Faculty of Medicine, Leicester Royal Infirmary, UK.
D003497:Cyclic N-Oxides; D004578:Electron Spin Resonance Spectroscopy / Q000295:instrumentation*; D004582:Electronics, Medical; D006801:Humans; D007211:Indoles; D008961:Models, Structural; D009942:Organometallic Compounds; D012680:Sensitivity and Specificity; D013113:Spin Labels
D003497:Cyclic N-Oxides; D007211:Indoles; D009942:Organometallic Compounds; D013113:Spin Labels; C081756:lithium phthalocyanine; C003959:TEMPO