Comparison of local transmit antennas for extremity imaging in MRI

MRI rf excitation with various local transmit antennas has been compared to the commonly used full-body transmit antenna in terms of transmit field distribution, field strength and local SAR. The antennas (volume and surface coils) have been designed, decoupled and matched by using a 3D field simulation software. The examined objects, a liquid-filled cylindric phantom and the arm of a human body model have been included in the simulation setup. According to this study, the use of local transmit coils results in an immense reduction of required transmit power and a saving potential of local SAR, independent of the choice of local antenna type. However, concerning homogeneity birdcage coils offer the best performance.