title: Segmented surface coil resonator for in vivo EPR applications at 1.1GHz.
abstract: A four-loop segmented surface coil resonator (SSCR) with electronic frequency and coupling adjustments was constructed with 18mm aperture and loading capability suitable for in vivo Electron Paramagnetic Resonance (EPR) spectroscopy and imaging applications at L-band. Increased sample volume and loading capability were achieved by employing a multi-loop three-dimensional surface coil structure. Symmetrical design of the resonator with coupling to each loop resulted in high homogeneity of RF magnetic field. Parallel loops were coupled to the feeder cable via balancing circuitry containing varactor diodes for electronic coupling and tuning over a wide range of loading conditions. Manually adjusted high Q trimmer capacitors were used for initial tuning with subsequent tuning electronically controlled using varactor diodes. This design provides transparency and homogeneity of magnetic field modulation in the sample volume, while matching components are shielded to minimize interference with modulation and ambient RF fields. It can accommodate lossy samples up to 90% of its aperture with high homogeneity of RF and modulation magnetic fields and can function as a surface loop or a slice volume resonator. Along with an outer coaxial NMR surface coil, the SSCR enabled EPR/NMR co-imaging of paramagnetic probes in living rats to a depth of 20mm.
authors.affiliation: Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart & Lung Research Institute and the Division of Cardiovascular Medicine, Department of Internal Medicine, The Ohio State University College of Medicine, Columbus, OH 43210, USA.
authors.forename: Sergey
authors.initials: S
authors.lastname: Petryakov
authors.forename: Alexandre
authors.initials: A
authors.lastname: Samouilov
authors.forename: Michael
authors.initials: M
authors.lastname: Chzhan-Roytenberg
authors.forename: Eric
authors.initials: E
authors.lastname: Kesselring
authors.forename: Ziqi
authors.initials: Z
authors.lastname: Sun
authors.forename: Jay L
authors.initials: JL
authors.lastname: Zweier
mesh_terms: D000465:Algorithms; D000818:Animals; D002606:Charcoal; D004574:Electromagnetic Fields; D004578:Electron Spin Resonance Spectroscopy / Q000295:instrumentation*; D004867:Equipment Design; D005260:Female; D008279:Magnetic Resonance Imaging; D010092:Oximetry; D051381:Rats
chemical_list: D002606:Charcoal