Transceiver-Phased Arrays for Human Brain Studies at 7 T

The paper describes technological advances in high-field (7 T) transceiver-phased arrays developed for magnetic resonance imaging of the human brain. The first part of this work describes an 8-element inductively decoupled split elliptical transceiver-phased array with selectable geometry, which provides an easy and efficient way of compensating for changes in mutual inductive coupling associated with difference in loading due to variability in head shape and size. The second part of the work describes a double-row 16-element (2 9 8) transceiver array to extend the homogeneous transmit B-1 profile in the longitudinal direction. Multiplexing eight transmit channels between the two rows of the array provides homogeneous excitation over the entire volume. The final section describes design and construction of a double-tuned P-31/H-1 16-element (8 at each frequency) array. The array improves transmission efficiency and B-1 homogeneity at H-1 frequency in comparison with P-31/H-1 quadrature transverse electromagnetic volume coil. For P-31 studies, the array also improves transmission efficiency (38%), signal-to-noise ratio (SNR) for central brain locations (20%) and provides substantially greater SNR (up to 400%) for peripheral locations.