Picker International, Inc.

Robert A Elek

Ravi Srinivasan

Haiying Liu

Robert G Henderson

A less-claustrophobic, quadrature, radio-frequency head coil (42) includes first and second broken end rings (90, 92) connected to each other in parallel by a plurality of leg conductors (94). At least two of the leg conductors are interconnected by a third arcuate conductor segment (98) axially displaced from planes of the first and second end rings to provide an opening (44) over a subject's face. The opening reduces patient claustrophobia and permits access to the patient for life-support devices or the practice of interventional medicine. The end rings have a fixed capacitance (C.sub.1, C.sub.2) between each pair of leg conductors. The fixed capacitance C.sub.1 between at least one pair of leg conductors and the fixed capacitance C.sub.2 between at least the pair of leg conductors adjacent the opening, where C.sub.2 &gt;C.sub.1. A two-port feed (66, 68) circumferentially attached to the coil generally opposite the opening matches the individual linear modes. Thus, the radio frequency coil is able to maintain two preferred principal linear modes (A, B) across the open area of the coil.

Less-claustrophobic, quadrature, radio-frequency head coil for nuclear

A magnetic resonance system is used to excite high .gamma. dipoles, such as hydrogen, and lower .gamma. dipoles, such as phosphorous, to resonate concurrently. A multiply-tuned radio frequency coil (40) is disposed around the region of interest. The multiply-tuned radio frequency coil is tuned to the resonance frequency of the high .gamma. dipoles and the resonance frequency of the low .gamma. dipoles. The coil has an inner coil section, defined by a first leg or ring (92) and a second leg or ring (94), which is tuned by added capacitance substantially to the resonance frequency of the low .gamma. dipole. A first outer coil section which is defined by a third leg or ring (90) and the first leg or ring. A second outer coil section defined by the second leg or ring (94) and a fourth leg or ring (96). The first and second outer sections, together with the inner coil section define a coil which has a co-rotating mode and a counter-rotating mode. Added capacitance is sized such that one of the co-rotating and counter-rotating modes is at the high .gamma. resonance frequencies. In this manner, a multiply-tuned radio frequency coil is defined which is simultaneously tuned to at least two resonance frequencies. Separate pick-ups (130, 132) for the high and low resonance frequencies enable both signals to be received (66, 70) simultaneously for reconstruction (74) into image representations.

Multipl-tuned radio frequency coil for simultaneous magnetic resonance

A coil assembly (40) includes a first, birdcage type head coil assembly (42) dimensioned to receive a patient's head and a second, neck coil assembly (44) including an anterior coil portion (44a) and a posterior coil portion (44b) dimensioned to receive the patient's neck region. The head and neck coils are partially overlapped. A first cable extends (98a) from the anterior coil portion past the birdcage head coil assembly and a second coaxial cable (98b) extends from the posterior portion past the birdcage head coil assembly. A first decoupling circuit (104a) is disposed in the first coaxial cable beyond a guard ring (106) and a second decoupling circuit (104b) is disposed in the second coaxial cable adjacent the region of overlap between the head and neck coil assemblies. The decoupling circuits are positioned and tuned to prevent radio frequency communication along the coaxial cable sheath between the head and neck coil assemblies. The head and neck coil assemblies are mounted in the mechanical housing which is openable such that an upper half of the guard ring and the birdcage coil and the anterior coil are removable as a unit from the lower half of the guard ring and birdcage coil and the posterior neck coil to facilitate patient access.

Split-top, neck and head vascular array for magnetic resonance imaging

In a magnetic resonance imaging apparatus, a radio frequency coil (40) is disposed closely adjacent the patient's head. The radio frequency coil includes a first annular ring (80, 114) around the patient's head from which a first plurality of legs (82, 116) extend. Opposite legs are interconnected equidistant from the first annular ring to form a virtual ground connection (84, 118). In the embodiment of FIG. 6, a second annular ring (120) is disposed parallel to the first annular ring with a second plurality of legs (122) extending between the first and second annular rings. By adjusting a ratio .rho. of the current flow in the loops defined by the first legs, the first annular ring and virtual ground relative to the current loops defined by the second legs and the first and second annular rings, the linearity of the B.sub.1 field within the head coil is selectively adjustable (FIG. 8).

Quadrature radio frequency coil for magnetic resonance imaging

A birdcage coil (42) and a quadrature coil pair which are disposed in a partially overlapping but electrically isolated relationship within a static magnetic field generated by a main field magnet (10). The birdcage coil preferably has twelve legs, has eight-fold symmetry, and is tuned to have two linear modes aligned with first and second orthogonal axes. The quadrature coil includes a first or upper coil portion (90) having an even-number of legs and a mode aligned with a third axis. A second or bottom quadrature coil (92) has an odd-number of legs and has a mode which is aligned with a fourth axis, preferably orthogonal to the third axis. Received resonance signals of the two modes of the birdcage coil are combined (66) and digitized (64); resonance signals received in the first and second modes of the quadrature coil pair are combined (66) and digitized (64). The digitized magnetic resonance signals are reconstructed (72) into an image representation, selective portions of which are displayed on a video monitor (52). Biasing voltages (106) are selectively applied to the birdcage and quadrature coils in order to deactivate one of the coils such that only the other coil receives resonance signals.

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Chardon, OH, United States of America

Robert A Elek