The MRI Eigencoil: 2N-Channel SNR with N-Receivers

= ss which is just a SoS operation in the new basis. Due to some basic symmetry existing between the n-elements of an array and therefore N, there may be some degeneracy between the eigenmodes. The number of degenerate eigenmodes (d) means the n-element phased array has degree m = n - d < n. Degenerate eigenmodes can be linearly mixed (preserving there eigenvalue) to produce new eigenmodes with most of the SNR concentrated in one of the two modes, leaving almost all the SNR contained in m-channels. This, of course, is the principle of Quad/Antiquad pairs now extended to higher degrees. Images were collected on a Siemens 1.5T Symphony 8 channel scanner using the Siemens 8-Channel Head Array (3), with elements equally separated by π/4 around the head. The Eigencoil TM was formed by inserting an m-degree K' -1 hardware combiner inline between the output of the Head Array and the system interface.