Magnetic resonance device

1. A magnetic resonance apparatus comprising:

a cryostat having an inner bore extending therethrough;

a gradient coil assembly located within said inner bore of the cryostat;

a seal between said gradient coil assembly and said inner bore; and

said seal comprising:

a first toroid mounted concentrically with respect to said gradient coil assembly and defining a first interior volume filled with a first fluid, and

a second toroid defining a second interior volume filled with a second fluid, wherein said second toroid is disposed within said first fluid filling said first interior volume of said first toroid, and wherein said first toroid and said second toroid are substantially concentric.

2. An apparatus as claimed in claim 1 wherein said gradient coil assembly has opposite ends, and wherein said seal is a first seal located at a first of said opposite ends of said gradient coil assembly, and wherein said apparatus comprises a second seal comprising:

a third toroid mounted concentrically with respect to said gradient coil assembly and defining a third interior volume filled with said first fluid, and

a fourth toroid defining a fourth interior volume filled with said second fluid, wherein said fourth toroid is disposed within said first fluid filling said third interior volume of said third toroid, and wherein said third toroid and said fourth toroid are substantially concentric,

said second seal being located at a second of said opposite ends of said gradient coil assembly.

3. An apparatus as claimed in claim 2 wherein said first and second seals have a space therebetween, and wherein said space is evacuated.

4. An apparatus as claimed in claim 1 wherein said first fluid is a liquid, and wherein said second fluid is a gas.

5. An apparatus as claimed in claim 4 wherein said gas in said second toroid is at a higher pressure than the liquid in said first toroid.

6. An apparatus as claimed in claim 4 comprising a cooling circuit, and wherein said cooling circuit cools said liquid in said first toroid.

7. An apparatus as claimed in claim 4 wherein said gas is selected from the group consisting of air, argon and nitrogen.

8. An apparatus as claimed in claim 1 wherein said first fluid is a gas and wherein said second fluid is a liquid.

9. An apparatus as claimed in claim 1 wherein said first toroid comprises a layflat hose.

10. An apparatus as claimed in claim 1 comprising a plurality of further seals situated around said gradient coil assembly.

11. An apparatus as claimed in claim 10 wherein each of said further seals comprises a fluid-filled toroid.

12. An apparatus as claimed in claim 10 wherein said plurality of further seals are respectively substantially equally spaced along a length of said gradient coil assembly.

13. An apparatus as claimed in claim 10 wherein each of said plurality of further seals is saddle-shaped.

14. An apparatus as claimed in claim 10 wherein each of said seal and said plurality of further seals has a pressure and a spring constant that is adjusted to set an orientation of said gradient coil assembly within said inner bore.

15. An apparatus as claimed in claim 10 wherein said gradient coil assembly comprises a resin former and gradient coils embedded therein, and wherein said former has a plurality of grooves therein in which said seal and said further seals are respectively seated.

16. An apparatus as claimed in claim 1 wherein said gradient coil assembly comprises a resin former and gradient coils embedded therein, said resin former having a groove therein in which said seal is seated.

17. A magnetic resonance apparatus comprising:

a cryostat having an inner bore extending therethrough;

a gradient coil assembly situated within said inner bore of said cryostat;

a seal between said gradient coil assembly and said inner bore; and

said seal comprising:

a first helix mounted concentrically with respect to said gradient coil assembly and defining a first interior volume filled with a first fluid, and

a second helix defining a second interior volume filled with a second fluid, wherein said second helix is disposed within said first fluid filling said first interior volume of said first helix, and wherein each turn of said first helix is substantially concentric with a corresponding turn of said second helix.

18. An apparatus as claimed in claim 17 wherein said first fluid is a liquid and wherein said second fluid is a gas.

19. An apparatus as claimed in claim 18 comprising a cooling circuit in communication with said liquid in said first helix to cool said liquid.

20. An apparatus as claimed in claim 1 , wherein the gradient coil assembly and the inner bore are cylindrical.