title: Generalized electrical analysis of low-pass and high-pass birdcage resonators.
abstract: The radio-frequency 'birdcage resonator' has found wide use in MRI/MRS for its field homogeneity and signal-noise characteristics. This paper presents a general analysis, derived from lumped element transmission line theory, of the electrical behavior of unloaded, N-column birdcage resonators applicable to several versions of the basic design including low-pass and high-pass coils. Analytic expressions and computer results are presented for both types of coil describing resonant frequencies, input and characteristic impedances, dispersion relations, pass-bands, resonant peak bandwidth and Q. Theoretical expressions for normalized resonant frequency difference ratios independent of element values and resonator geometry have been developed for generic low- and high-pass coils. Experimental measurements of resonant frequencies were made for six coils, and the average agreement with theoretical predictions was approximately 4%.
authors.affiliation: Department of Electrical Engineering, Manhattan College, Riverdale, New York 10471.
authors.forename: R J
authors.initials: RJ
authors.lastname: Pascone
authors.forename: B J
authors.initials: BJ
authors.lastname: Garcia
authors.forename: T M
authors.initials: TM
authors.lastname: Fitzgerald
authors.forename: T
authors.initials: T
authors.lastname: Vullo
authors.forename: R
authors.initials: R
authors.lastname: Zipagan
authors.forename: P T
authors.initials: PT
authors.lastname: Cahill
mesh_terms: D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation* / Q000379:methods; D055585:Physical Phenomena; D010825:Physics