Birdcage Coil with Inductively Coupled RF Coil Array for Improving |B₁|-Field Sensitivity In 7-T MRI

A birdcage coil integrated with a 16-channel, inductively coupled, radio-frequency (RF) array was designed to improve the magnetic-flux distribution for human brain magnetic resonance imaging at 7-T. A numerical calculation was performed using the finite-difference time-domain method for the birdcage coil with an inductively coupled array. The electromagnetic calculation results for the birdcage coil with the inductively coupled array were compared to those for the birdcage coil without an inductively coupled array in terms of their magnetic- flux, electric-field, and specific-absorption-rate distributions in a cylindrical phantom and human model. The proposed birdcage coil with an inductively coupled array offers a superior magnetic-flux sensitivity without sacrificing the RF power deposition at 7-T. The modifications of the coil geometry accompanying the inductively coupled RF array could be applied to the generally used transmit/receive volume coils and extended to parallel RF transmission array in ultra-high-field magnetic resonance imaging.