title: A numerical approach to non-circular birdcage RF coil optimization: verification with a fourth-order coil.
abstract: It is demonstrated that birdcage resonators, satisfying conditions of quadrature operation and radiofrequency field homogeneity, can be realized in practice on formers of non-circular cross section described by an equation of the form (x/a)n + (y/b)n = 1 where a and b are constants and n > or = 2 is an integer. Using a ladder network analogous to that of a conventional circular birdcage, optimization algorithms were employed to determine the elemental current distribution on the non-circular cylindrical surfaces. A comparison of circular, elliptical, symmetric and asymmetric fourth-order (n = 4) section birdcage current distributions is presented. A short, asymmetric fourth-order cage was constructed and tested experimentally at 3 T and compared with a conventional circular-section head coil.
authors.affiliation: Department of Biomedical Engineering, University of Alberta, Edmonton, Canada.
authors.forename: T A
authors.initials: TA
authors.lastname: Riauka
authors.forename: N F
authors.initials: NF
authors.lastname: De Zanche
authors.forename: R
authors.initials: R
authors.lastname: Thompson
authors.forename: F E
authors.initials: FE
authors.lastname: Vermeulen
authors.forename: C E
authors.initials: CE
authors.lastname: Capjack
authors.forename: P S
authors.initials: PS
authors.lastname: Allen
mesh_terms: D000465:Algorithms; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation* / Q000379:methods