Applications of RF current sources for transmit phased array

Current practice in MRI trends towards higher static magnetic field (B₀) because of the advantage of signal-to-noise ratio (SNR). However at high magnetic fields, the interaction between a coil and a load becomes significant, thus making current distribution on RF coils disturbed and causing transverse magnetic (B₁) field inhomogeneity. A novel approach to optimize B₁, field homogeneity is to use a transmit phased array and adjust the amplitudes and phases of the currents on each element independently. However, independent control is difficult to achieve in conventional arrays due to coupling between elements. In addition, the currents are generally load dependent. In this paper we show that a RF current source is an effective method for controlling the current on each element of the transmit phased array, and that the RF current source is much less sensitive to loading and a interelement coupling than a conventional 50Ω matched coil.