A numerical approach to non-circular birdcage RF coil optimization: verification with a fourth-order coil.
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.
Riauka
T A
TA
Department of Biomedical Engineering, University of Alberta, Edmonton, Canada.
De Zanche
N F
NF
Thompson
R
R
Vermeulen
F E
FE
Capjack
C E
CE
Allen
P S
PS
D000465:Algorithms; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation* / Q000379:methods