Mitigation of B1+ inhomogeneity on single-channel transmit systems with TIAMO

Abstract

In magnetic resonance imaging, there has been a constant drive to higher static magnetic field strengths (B0) to achieve a higher signal-to-noise ratio and new or enhanced contrasts. In today's high-field systems, severe problems regarding the homogeneity of the transmission field are encountered. Recently, an acquisition scheme called Time-Interleaved Acquisition of Modes has been proposed to tackle the inhomogeneity problems in high-field magnetic resonance imaging. The basic premise is to excite two (or more) different B 1+ modes using static radiofrequency shimming in an interleaved acquisition, where the complementary radiofrequency patterns of the two modes can be exploited to improve overall signal homogeneity. In its usual implementation, a multichannel transmit system is required. In this work, the goal is to present a simple and inexpensive hardware setup which makes it possible to use time-interleaved acquisition of modes on any single-channel transmit system while making use of the vendor-provided single-channel radiofrequency safety system. To demonstrate the efficacy of this setup, spin echo images from the pelvis are acquired at 7 T exhibiting no complete signal dropouts. © 2012 Wiley Periodicals, Inc.