Parallel coil resonators for time-domain radiofrequency electron paramagnetic resonance imaging of biological objects

Resonators suitable for time-domain electron paramagnetic resonance spectro scopy and imaging at a radiofrequency capable of accommodating experimental animals such as mice are described. Design considerations included B-1 fie ld homogeneity, optimal Q, spectral bandwidth, resonator ring-down, and sen sitivity. Typically, a resonator with 25-mm diameter and 25-mm length was c onstructed by coupling 11 single loops in parallel with a separation of 2.5 mm. To minimize the resonator ring-down time and provide the necessary spe ctral bandwidth for in vivo imaging experiments, the Q was reduced predomin antly by overcoupling. Capacitative coupling was utilized to minimize micro phonic effects. The B-1 field in the resonator was mapped both radially and axially and found to be uniform and adequate for imaging studies. Imaging studies with phantom objects containing a narrow-line spin probe as well as in vivo objects administered with the spin probe show the suitability of t hese resonators for valid reproduction of the spin probe distribution in th ree dimensions. The fabrication of such resonators is simple and can be sca led up with relative ease to accommodate larger objects as well. (C) 2000 A cademic Press.