Open half volume quadrature transverse electromagnetic coil for high field magnetic resonance imaging
View Patent ↗A half-volume quadrature TEM coil high field (>3 T) imaging applications. This novel coil produces a sufficiently large homogeneous B 1 field region for the use as a volume coil. It provides superior transmission efficiency, resulting in significantly lower power deposition, as well as greater sensitivity and improved patient comfort and accessibility compared with conventional full-volume coils. Additionally this coil compensates the RF penetration artifact that distorts high-field images recorded with linear surface and volume coils. These advantages make it potentially possible to apply the device as an efficient transmit/receive body coil at high fields, where the use of the full-volume coils is complicated by the excessive power deposition and low sensitivity.
1. An open volume quadrature transverse electromagnetic coil comprising:
a plurality of inductively coupled resonant transmission line elements adapted to be driven to resonate in a first mode and a second mode; and
a quadrature driver circuit operatively associated with said transmission line elements for driving said coil in said first mode and said second mode simultaneously,
wherein one of said first and second modes is associated with at least one nodal point in said coil, at least one of said transmission line elements located at one of said at least one nodal point such that the mode associated with said nodal point induces no current in said at least one transmission line element, and wherein the other of said first and second modes is driven from said element in said nodal point.
2. The device of claim 1 wherein said first mode is a surface mode and said second mode is a butterfly mode.
3. The device of claim 2 having a first element and a last element, wherein said coil is driven in said surface mode in such a manner to maintain approximately a 180 degree phase shift between said first and last elements.
4. The device of claim 3 wherein said surface mode and said butterfly mode are be driven and tuned independently.
5. The device of claim 3 wherein said quadrature driver circuit includes a symmetrized matching network for driving said coil in the surface mode.
6. The device of claim 4 wherein said butterfly mode is driven at one of said at least one elements located within said nodal point of the surface mode.
7. The device of claim 2 wherein said coil is comprised of seven elements, having a first and last element and a center element, said center element located within said at least one nodal point.
8. The device of claim 7 wherein said center element is located within a nodal point associated with said surface mode.
9. The device of claim 8 wherein said butterfly mode is driven from said center element.
10. The device of claim 2 wherein said coil is comprised of nine elements, having a center element located within said at least one nodal point.
11. The device of claim 10 wherein said center element is located within a nodal point associated with said surface mode.
12. The device of claim 11 wherein at least two of said nine elements other than said center element are located within nodal points associated with said butterfly mode.