Performance comparison of 8, 16 and 32 column RF birdcage resonators

This study compares performance characteristics for birdcage coils having 8, 16 and 32 columns. Self and effective (self plus mutual) inductances and resistances were calculated for 6 coils having 8, 16 and 32 columns, and quality factors were determined using self (Q_s) and effective (Q_e) inductances. Q_s decreased with increasing number of columns where the average Q_s ratio for column ratios of 16:8 and 32:8 were 0.85 and 0.65, respectively. Q_e increased with increasing number of columns, where the values for 16:8 and 32:8 were 1.05 and 1.11. Using Biot-Savart calculations, improved field uniformity was seen with a greater number of columns. This study quantified the advantage of fabricating birdcage coils with a greater number of columns