Investigation Non-magnetic Amplifiers Applied in an MRI System

INTRODUCTION: In our previous work on passive current source RF power amplifiers, it was noted that additional inter-element isolation in a parallel transmit coil array was possible when the lengths of the coaxial cables that connected the amplifiers to the coils were reduced [1,2]. In addition, shorter cable lengths also lead to reduced power loss and cost. This can be achieved by placing the RF amplifiers near the magnet (e.g., on front panel or side of the bore) and requires that the amplifiers are compatible within a high magnetic field environment. To accomplish this, the B0 field should have no adverse impact on MOSFET and amplifier behavior, and, the amplifier should also have no notable impact on image quality. In this study, a 1 kW (peak power) non-magnetic amplifier module was designed and constructed. The impact of the B0 field on the non-magnetic amplifier and the effect of non-magnetic amplifier on the performance of the system were investigated on a GE 3T MR750 system (GE Healthcare, Waukesha, WI). The experimental results indicated that, at 3T, the magnetic field had no notable impact on the AC and DC characteristic of the power MOSFET. Similarly, the non-magnetic amplifier had no appreciable impact on B0 and B1 homogeneity, and, image SNR.