A Review of Current Control and Decoupling Methods for MRI Transmit Arrays.

The shortened radio frequency wavelength in high field MRI makes it challenging to create a uniform excitation pattern over a large field of view, or to achieve satisfactory transmission efficiency at a local area. Transmit arrays are one tool that can be used to create a desired excitation pattern. To be effective, it is important to be able to control the current amplitude and phase at the array elements.

An eight-channel T/R head coil for parallel transmit MRI at 3T using ultra-low output impedance amplifiers.

Parallel transmit is an emerging technology to address the technical challenges associated with MR imaging at high field strengths. When developing arrays for parallel transmit systems, one of the primary factors to be considered is the mechanism to manage coupling and create independently operating channels. Recent work has demonstrated the use of amplifiers to provide some or all of the channel-to-channel isolation, reducing the need for on-coil decoupling networks in a manner analogous to the use of isolation preamplifiers with receive coils.

Highly parallel transmit/receive systems for dynamic MRI.

Dynamic MRI continues to grow in interest and capability with the introduction of 64 and 128 channel receivers, and, more recently, 8 and 16 channel parallel transmitters. This talk will describe progress in developing a 64 channel transmitter and applications in high-speed MR imaging, reaching 1000 frames per second.