Crossed-ladder RF coils for vertical field MRI systems

A magnetic resonance apparatus having an examination region through which a temporally constant main magnetic field B0 is generated, an RF transmitter which excites resonance in selected dipoles in the examination region such that the dipoles generate resonance signals at a characteristic resonance frequency, a radio frequency coil assembly which receives resonance signals from the resonating dipoles, at least one radio frequency receiver for demodulating the received resonance signals from the quadrature RF coil assembly, the quadrature RF coil assembly comprising:

• a first RF ladder coil which receives a uni-directional B1 field component parallel to a first axis;
• a second RF ladder coil disposed partially overlapping and rotated 90° relative to the first ladder coil, said second ladder coil receiving a uni-directional B1 field component parallel to a second axis orthogonal to the first axis;
• and
• a third RF ladder coil disposed partially overlapping and rotated 90° relative to the second ladder coil, said third ladder coil receiving a uni-directional B1 field parallel to the first axis;
• the first, second, and third RF ladder coils being disposed on the same side of the examination region.

A magnetic resonance apparatus having an examination region through which a temporally constant main magnetic field B0 is generated, an RF transmitter which transmits radio frequency pulses to a quadrature radio frequency coil assembly to excite resonance in selected dipoles in the examination region such that the dipoles generate resonance signals at a characteristic resonance frequency, said quadrature radio frequency coil assembly receiving resonance signals from the resonating dipoles, at least one radio frequency receiver for demodulating the resonance signals received from the quadrature RF coil assembly, the quadrature RF coil assembly comprising:

• a first RF ladder coil disposed in a parallel relationship to pole pieces;
• a second RF ladder coil disposed in a parallel relationship to the pole pieces adjacent the first RF ladder coil, the second RF ladder coil being rotated by 90° relative to the first RF ladder coil;
• a third RF ladder coil disposed partially overlapping the first RF ladder coil, the third RF ladder coil being rotated 90° relative to the first RF ladder coil;
• and,
• a fourth RF ladder coil disposed partially overlapping the second RF ladder coil, the fourth RF ladder coil being rotated 90° relative to the second RF ladder coil.

A crossed-ladder RF coil for an open magnetic resonance imaging system in which a B0 main magnetic field is generated through an examination region, said crossed-ladder RF coil comprising:

• a first tuned ladder coil and a second tuned ladder coil disposed in a parallel relationship to each other and substantially orthogonal to the B0 field, the first and second ladder coils being rotated by 90° relative to one another;
• a third RF ladder coil disposed partially overlapping the first RF ladder coil, the third RF ladder coil being rotated 90° relative to the first RF ladder coil;
• and,
• a fourth RF ladder coil disposed partially overlapping the second RF ladder coil, the fourth RF ladder coil being rotated 90° relative to the second RF ladder coil.

A method of magnetic resonance imaging in which a temporally constant main magnetic field is generated through an examination region, the method including:

• (a) tuning a first ladder RF coil to a first B1 mode component which is parallel to the first ladder RF coil,
• (b) positioning the first ladder RF coil in a plane transverse to the main magnetic field on one side of the examination region;
• (c) tuning a second ladder RF coil to a second B1 mode component that is parallel to the second ladder RF coil;
• (d) positioning the second ladder RF coil in a plane parallel to the first ladder RF coil, said first and second ladder coils being rotated by 90° relative to one another such that the first and second B1 mode components are orthogonal to one another;
• (e) exciting magnetic resonance in dipoles of interest in the examination region;
• (f) receiving induced magnetic resonance signals in quadrature by receiving the first B1 mode component with the first RF ladder coil and the orthogonal second B1 mode component with the second ladder coil;
• and
• (g) reconstructing the received magnetic resonance signals into an image representation.

A method of magnetic resonance imaging in which a temporally constant main magnetic field is generated through an examination region, the method including:

• (a) tuning a first ladder RF coil to a first B1 mode component which is parallel to the first ladder RF coil,
• (b) positioning the first ladder RF coil in a plane transverse to the main magnetic field on one side of the examination region;
• (c) tuning a second ladder RF coil to a second B1 mode component that is parallel to the second ladder RF coil;
• (d) positioning the second ladder RF coil in a partially overlapping relationship to the first ladder RF coil such that the mutual inductance between the coils is minimized, said first and second ladder coils being rotated by 90° relative to one another such that the first and second B1 mode components are orthogonal to one another;
• and,
• (e) reconstructing the received magnetic resonance signals into an image representation.

A method of magnetic resonance imaging in which a temporally constant main magnetic field is generated through an examination region, the method including:

• (a) tuning a first ladder RF coil to a first B1 mode component which is parallel to the first ladder RF coil,
• (b) positioning the first ladder RF coil in a plane transverse to the main magnetic field on one side of the examination region;
• (c) tuning a second ladder RF coil to a second B1 mode component that is parallel to the second ladder RF coil;
• (d) positioning the second ladder RF coil on an opposite side of the examination region spaced apart from the first ladder RF coil, said first and second ladder coils being rotated by 90° relative to one another such that the first and second B1 mode components are orthogonal to one another;
• (e) receiving induced magnetic resonance signals in quadrature by receiving the first B1 mode component with the first RF ladder coil and the orthogonal second B1 mode component with the second ladder coil;
• and
• (f) reconstructing the received magnetic resonance