USE OF TRANSMISSION-LINE ANALYSIS FOR MULTI-TUNING OF BIRDCAGE RESONATORS

A general analysis for double- and higher order tuning of birdcage res onators is presented based on a lumped element transmission line model . Expressions were developed for the determination of the resonant fre quencies of bandstop and bandpass birdcage coils and, with specified r estrictions, for capacitor values required to obtain any two desired m ode one resonant frequencies. Experimental measurements on three varia nts each of an eight-column bandstop and an eight-column bandpass were in excellent agreement with theory; the average absolute frequency di fference and percent deviation were 1.51 +/- 1.57 MHz and 2.61 +/- 2.3 6%, respectively. In addition, P-31 and H-1 phantom images were obtain ed at 2.0 T using a representative bandstop coil.