Accurate calculation of mutual inductance and magnetic fields in a birdcage coil
Résumé
We present a detailed and complete analysis of a birdcage coil designed for MRI experiment through an equivalent circuit model. We derive analytic equations which can be used to predict a priori the full mutual inductances between conductors and the complete resonant spectrum for unshielded coils with high accuracy. The equations are valid for lowpass, highpass, and bandpass structures. We show that the approximation of a sinusoidal current pattern--which is usually used in the literature--is justified. Moreover, we reduce Neumann formula to the computation of two integrals and present an accurate algorithm to compute them. We also compute the magnetic field pattern of a birdcage coil. Our model is validated through numerical simulations which are compared to experimental results.