Electricity: measuring and testing – Particle precession resonance – Spectrometer components
Reexamination Certificate
1998-06-11
2001-03-27
Oda, Christine K. (Department: 2862)
Electricity: measuring and testing
Particle precession resonance
Spectrometer components
C324S309000, C324S307000
Reexamination Certificate
active
06208141
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the magnetic resonance art. It finds particular application in conjunction with a method and apparatus for mounting a gradient tube to a magnetic resonance imaging (MRI) device and will be described with particular reference thereto. However, it should be appreciated that the present invention may also find application in conjunction with magnetic resonance spectroscopy systems and other applications which utilize gradient tubes.
In magnetic resonance imaging applications, three orthogonal gradient fields are employed to provide spatial resolution by frequency discrimination of an MRI signal. A gradient tube typically includes three discrete gradient coils for generating the x, y, and z-gradient fields. The discrete coils are insulated from each other and are layered on a cylindrical former. Commonly, the entire gradient tube is overwrapped and epoxy impregnated for greater structural strength.
A self-shielded gradient tube typically includes a secondary or shielding gradient coil set spaced radially from a primary gradient coil set. The primary and secondary gradient coil sets each include insulated coils for generating x, y, and z-gradient fields which can be layered on separate cylindrical formers or on a single unitary former.
Both types of gradient tubes must be constrained in the x, y, and z directions when mounted within the cylindrical bore of an MRI magnet housing due to the magnetic forces acting on the gradient tube. The gradient tube is typically secured to the magnet housing by mounting rings positioned at both ends of the cylindrical bore to, in effect, trap the gradient tube between the mounting rings. However, the mounting ring design makes the front tunnel liner design much more claustrophobic from the patient's perspective, in addition to limiting access to the patient by medical personnel. Further, mounting rings interfere with service-end water headers on liquid-cooled gradient tubes making the designs complex and costly.
In an alternative arrangement, the gradient tube can be mounted to tombstone-like castings secured to the floor and located at the patient and service-ends of the magnet housing. However, the tombstone gradient tube mounts make the MRI device substantially longer, making access to the patient more difficult.
The present invention contemplates a new and improved method and apparatus for mounting a gradient tube to an MRI device which overcomes the above-referenced problems and others.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, there is provided a diagnostic imaging apparatus including a housing, a main field magnet for generating a temporally constant magnetic field through an examination region defined within a bore of the housing, and a gradient tube assembly positioned within the bore for inducing gradient magnetic fields across the temporally constant magnetic field. The gradient tube assembly includes at least one tongue member extending from the gradient tube assembly, and at least one mount for securing the at least one tongue member to the housing, said mount restraining the gradient tube assembly in a direction at least along a z-axis extending through the bore.
In accordance with a second aspect of the present invention, there is provided a method of securing a gradient tube assembly to a housing of a diagnostic imaging apparatus wherein the gradient tube assembly is positioned within a bore of the housing. The method includes attaching a tongue member associated with the gradient tube assembly to a mount associated with the housing to restrain the gradient tube assembly in a direction at least along a z-axis extending through the bore.
The invention provides a low cost gradient mounting with improved patient access due to larger openings in the tunnel liners. There is also much better service access to the service-end of the gradient tube for the bus bars and water header plumbing with the z-axis constraint located at the patient-end of the gradient tube.
One advantage of the present invention is that it provides a single “push-pull” type z-axis constraint at the patient end of the bore to permit free and needed space to be used at the service end of the bore for water cooling, electrical connections, etc.
Another advantage of the present invention is the provision of an integral mounting appendage or tongue at the patient-end of the gradient tube which is structurally reinforced by continuous glass filaments and of an optimized semi-circular shape.
Another advantage of the present invention is that it allows for a more open front tunnel linear design with a shorter bore length for easier access to the patient.
Another advantage of the present invention is that it reduces the cost of the gradient mounting and simplifies the design and installation of the gradient tube.
Further advantages reside in improved service access to the service end of the gradient tube for servicing the bus bars and water header plumbing.
Still further advantages of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.
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patent: 5786695 (1998-07-01), Amor et al.
patent: 5793210 (1998-08-01), Pla et al.
patent: 5990681 (1999-11-01), Richard et al.
patent: 6084409 (2000-07-01), Zebelein et al.
patent: 3833590A1 (1990-04-01), None
Alden, Sr. Jerome S.
Amor, Sr. William H.
Gruden James L.
Morich Michael A.
Fay Sharpe Fagan Minnich & McKee LLP
Fetzner Tiffany A.
Oda Christine K.
Picker International Inc.
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