Numerical design of RF Birdcage Coil without lumped elements for MRI 3T system

Abstract

This paper proposes a RF Birdcage Coil resonator without lumped elements. The RF Birdcage Coil resonator is designed without using lumped elements, which is able to resonate at 128 MHz for non-invasively 3T Magnetic Resonance Imaging (MRI) system. This resonator has the Leg and End Rings (ERs), which are composed from copper sheets and then they are attached on the inner and the outer of a circular acrylic as a substrate material in order to produce the capacitance of the resonator and to form a suitable RF Birdcage Coil's configuration. The ERs configuration is arranged to create the capacitance at each birdcage's edge. In order to generate a resonant frequency, the ER sheets should be tuned dimensionally to change each capacitance. The Birdcage Builder software is used to design the initial capacitance configuration of the resonator. Once each capacitance value of the configuration is obtained, then the resonator is numerically simulated by using electromagnetic (EM) simulator. The simulated results show good reflection coefficient at 128 MHz with uniform magnetic field strength distribution. In addition, the birdcage coil performance is also investigated by inserting numerical hand and head phantom models into the coil. The results show that the coil with head phantom is slightly shifted to 128 MHz, in comparison with the coil without human head model, which it resonates at 128.2 MHz.