title: Practical design of a 4 Tesla double-tuned RF surface coil for interleaved 1H and 23Na MRI of rat brain.
abstract: MRI is proving to be a very useful tool for sodium quantification in animal models of stroke, ischemia, and cancer. In this work, we present the practical design of a dual-frequency RF surface coil that provides (1)H and (23)Na images of the rat head at 4 T. The dual-frequency RF surface coil comprised of a large loop tuned to the (1)H frequency and a smaller co-planar loop tuned to the (23)Na frequency. The mutual coupling between the two loops was eliminated by the use of a trap circuit inserted in the smaller coil. This independent-loop design was versatile since it enabled a separate optimisation of the sensitivity and RF field distributions of the two coils. To allow for an easy extension of this simple double-tuned coil design to other frequencies (nuclei) and dimensions, we describe in detail the practical aspects of the workbench design and MRI testing using a phantom that mimics in vivo conditions. A comparison between our independent-loop, double-tuned coil and a single-tuned (23)Na coil of equal size obtained with a phantom matching in vivo conditions, showed a reduction of the (23)Na sensitivity (about 28 %) because of signal losses in the trap inductance. Typical congruent (1)H and (23)Na rat brain images showing good SNR ((23)Na: brain 7, ventricular cerebrospinal fluid 11) and spatial resolution ((23)Na: 1.25 x 1.25 x 5mm(3)) are also reported. The in vivo SNR values obtained with this coil were comparable to, if not better than, other contemporary designs in the literature.
authors.affiliation: Dipartimento di Scienze e Tecnologie Biomediche and CNR-INFM, Universita' dell'Aquila, L'Aquila 67100, Italy. marcello.alecci@univaq.it
authors.forename: M
authors.initials: M
authors.lastname: Alecci
authors.forename: S
authors.initials: S
authors.lastname: Romanzetti
authors.forename: J
authors.initials: J
authors.lastname: Kaffanke
authors.forename: A
authors.initials: A
authors.lastname: Celik
authors.forename: H P
authors.initials: HP
authors.lastname: Wegener
authors.forename: N J
authors.initials: NJ
authors.lastname: Shah
mesh_terms: D000818:Animals; D001921:Brain / Q000033:anatomy & histology*; D001927:Brain Diseases / Q000175:diagnosis; D004867:Equipment Design; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D019047:Phantoms, Imaging; D011846:Radio Waves; D051381:Rats; D012975:Sodium Isotopes
chemical_list: D012975:Sodium Isotopes