title: The design of a double-tuned two-port surface resonator and its application to in vivo hydrogen- and sodium-MRI.
abstract: The design and construction of a two-port surface transceiver resonator for both (1)H-and (23)Na-MRI in the rodent brain at 7 T is described. Double-tuned resonators are required for accurately co-registering multi-nuclei data sets, especially when the time courses of (1)H and (23)Na signals are of interest as, for instance, when investigating the pathological progression of ischaemic stroke tissue in vivo. In the current study, a single-element two-port surface resonator was developed wherein both frequency components were measured with the same detector element but with each frequency signal routed along different output channels. This was achieved by using the null spot technique, allowing for optimal variable tuning and matching of each channel in situ within the MRI scanner. The (23)Na signal to noise ratio, measured in the ventricles of the rat brain, was increased by a factor of four compared to recent state-of-the-art rat brain studies reported in the literature. The resonator's performance was demonstrated in an in vivo rodent stroke model, where regional variations in (1)H apparent diffusion coefficient maps and the (23)Na signal were recorded in an interleaved fashion as a function of time in the acute phase of the stroke without having to exchange, re-adjust, or re-connect resonators between scans. Using the practical construction steps described in this paper, this coil design can be easily adapted for MRI of other X-nuclei, such as (17)O, (13)C, (39)K, and (43)Ca at various field strengths.
authors.affiliation: School of Physics, Trinity College Dublin, University of Dublin, Ireland. wetterlf@tcd.ie
authors.forename: Friedrich
authors.initials: F
authors.lastname: Wetterling
authors.forename: Miroslav
authors.initials: M
authors.lastname: Högler
authors.forename: Ute
authors.initials: U
authors.lastname: Molkenthin
authors.forename: Sven
authors.initials: S
authors.lastname: Junge
authors.forename: Lindsay
authors.initials: L
authors.lastname: Gallagher
authors.forename: I
authors.initials: I
authors.lastname: Mhairi Macrae
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Fagan
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006859:Hydrogen / Q000032:analysis*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D008280:Magnetics / Q000295:instrumentation*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000032:analysis*; D014159:Transducers
chemical_list: D006859:Hydrogen; D012964:Sodium