Apparatus and method for fabricating magnet support structure

#The present invention relates generally to a superconductive magnet (such as, but not limited to, a helium-cooled and/or cryocooler-cooled superconductive magnet) used to generate a high magnetic field as part of a magnetic resonance imaging (MRI) system, and more particularly to such a magnet support structure in an MRI magnet having a closed design.

#MRI systems employing superconductive or other type magnets are used in various fields such as medical diagnostics. Known superconductive magnets include liquid-helium cooled and cryocooler-cooled superconductive magnets. Typically, for a helium-cooled magnet, the superconductive coil assembly includes a superconductive main coil which is at least partially immersed in liquid helium contained in a helium dewar which is surrounded by a dual thermal shield which is surrounded by a vacuum enclosure. In a conventional cryocooler-cooled magnet, the superconductive main coil is surrounded by a thermal shield which is surrounded by a vacuum enclosure, and the cryocooler coldhead is externally mounted to the vacuum enclosure with the coldhead's first stage in thermal contact with the thermal shield and with the coldhead's second stage in thermal contact with the superconductive main coil. Nb—Ti superconductive coils typically operate at a temperature of generally 4 Kelvin, and Nb—Sn superconductive coils typically operate at a temperature of generally 10 Kelvin.

#Known superconductive magnet designs include closed magnets and open magnets. Closed magnets typically have a single, tubular-shaped superconductive coil assembly having a bore. The superconductive coil assembly includes several radially aligned and longitudinally spaced-apart superconductive main coils each carrying a large, identical electric current in the same direction. The closed MRI magnet typically has a single superconductive coil assembly including a generally toroidal-shaped magnet support structure surrounding a bore and having a generally longitudinally extending axis. The magnet support structure also includes a pair of longitudinally spaced apart, generally identical, and generally annular-shaped superconductive main coils each generally coaxially aligned with the longitudinally extending axis. Each main coil typically carries a generally identical first electric current in an identical first electric-current direction. Each main coil is located within the superconductive coil assembly, and each main coil has a longitudinally outermost portion. The main coils are thus designed to create a magnetic field of high uniformity within a spherical imaging volume centered within the magnet's bore where the object to be imaged is placed. Closed MRI magnets tend to have a relatively long axial (i.e., longitudinal) length to accommodate the number of main superconductive coils needed to achieve a homogeneous imaging volume. The relatively long axial length tends to create claustrophobic feelings in patients, especially in the case of whole-body magnets.

#These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

#FIG. 1 is a cross sectional view along the longitudinal axis of the magnet support structure of one embodiment of the present invention;

#FIG. 2 is a Detail “A” of FIG. 1 that depicts a cross section of a portion of the left integral flange along the longitudinal axis of the magnet support structure of one embodiment of the present invention;

#The present invention provides a magnet support structure 1000 with one embodiment being depicted in FIG. 1. The magnet support structure 1000 comprises a cylindrical portion 200. The cylindrical portion 200 comprises a plurality of laminated composite layers 20 concentrically assembled to one another along a longitudinal axis 10. An integral left flange 25 comprises the laminated composite layers 20, which are concentrically assembled with respect to a left flange axis 45. The left flange axis 45 is perpendicular to the longitudinal axis 10. An integral right flange 30 comprises the laminated composite layers 20, which are concentrically assembled with respect to a right flange axis 50. The right flange axis 50 is perpendicular to the longitudinal axis 10. The plurality of laminated composite layers 20 comprises the base laminate 15 of FIG. 2. As used herein, the terms “integral left flange” and “integral right flange” mean that the same laminated composite layers 20 that comprise the cylindrical portion 200 also comprise the integral left flange 25 and the integral right flange 30.

#As used in the present invention, a coordinate system defines the radial, tangential, and axial directions, where the coordinate system is depicted in FIG. 1. In the coordinate system, a point P is located on an outer surface 40 of the cylindrical portion 200 using cylindrical polar coordinates (s, c, and a), defining the unit coordinate vectors, ŝ, ĉ, and â in the radial, circumferential, and axial directions, respectively. The angular orientation of the laminated composite layer 20, prepregs that comprise each laminated composite layer 20, and glass fibers that comprise each prepreg are described by the angle in the ĉ, â plane measured in the right-hand sense about the ŝ direction from the ĉ direction. The angular orientation is defined to have an angle in a range from −90 degrees to 90 degrees. In the present invention, the circumferential direction ĉ lies on a circumferential axis 12 and the axial direction â lies on the longitudinal axis 10.

#As used herein, the term “prepreg” is defined to include 90 degree prepregs 300 of FIG. 9, 0 degree prepregs 220 of FIG. 6, −45 degree prepregs 260 of FIG. 8, and 45 degree prepregs 240 of FIG. 7. As used herein, the term “glass fiber” is defined to include 90 degree glass fibers 290 of FIG. 9, 0 degree glass fibers 210 of FIG. 6, −45 degree glass fibers 250 of FIG. 8, and 45 degree glass fibers 230 of FIG. 7.