초록 ▼

Systems and methods for operating a magnetic resonance imaging (MRI) during ramping are provided. One method includes reducing pressure in a cryogen vessel of an MRI system during magnet ramping. The method also includes returning pressure in the cryogen vessel to a normal operating pressure level a

Systems and methods for operating a magnetic resonance imaging (MRI) during ramping are provided. One method includes reducing pressure in a cryogen vessel of an MRI system during magnet ramping. The method also includes returning pressure in the cryogen vessel to a normal operating pressure level after magnet ramping is complete.

대표청구항 ▼

1. A method for controlling a magnetic resonance imaging (MRI) magnet system, the method comprising: reducing pressure in a cryogen vessel of an MRI system to a pumped-down pressure level during magnet ramping; andincreasing the pressure in the cryogen vessel from the pumped-down pressure level to a

1. A method for controlling a magnetic resonance imaging (MRI) magnet system, the method comprising: reducing pressure in a cryogen vessel of an MRI system to a pumped-down pressure level during magnet ramping; andincreasing the pressure in the cryogen vessel from the pumped-down pressure level to a normal operating pressure level after magnet ramping is complete. 2. A method in accordance with claim 1 wherein reducing pressure comprises pumping gas out from the cryogen vessel using a vacuum pump. 3. A method in accordance with claim 1 wherein increasing pressure comprises adding gas to the cryogen vessel. 4. A method in accordance with claim 1 wherein reducing pressure comprises pumping gas out from the cryogen vessel until a temperature of cryogen in the cryogen vessel reaches a superfluid temperature. 5. A method in accordance with claim 1 wherein reducing pressure comprises pumping gas out from the cryogen vessel until a temperature of cryogen in the cryogen vessel reaches a temperature below a normal operating temperature. 6. A method in accordance with claim 1 wherein reducing pressure comprises pumping gas out from the cryogen vessel so the pressure reduces from about 100 kilo-Pascal (kPa) to about 5 kPa. 7. A method in accordance with claim 1 wherein the normal operating pressure level is about ambient pressure. 8. A method in accordance with claim 1 wherein reducing pressure comprises pumping gas out from the cryogen vessel prior to magnet ramping. 9. A method in accordance with claim 1 wherein the cryogen vessel comprises two chambers and reducing pressure comprises reducing pressure in one of the chambers to a pressure level significantly less than the other chamber. 10. A method in accordance with claim 9 wherein the reduced pressure is about 5 kilo-Pascal (kPa) and a pressure in the other chamber is about 100 kPa. 11. A method in accordance with claim 1 wherein the cryogen vessel comprises two chambers and reducing pressure comprises pumping cryogen liquid from one of the chambers such that the other chamber is sub-cooled without reducing a cryogen liquid level. 12. A method in accordance with claim 1 wherein the cryogen vessel comprises two chambers and reducing pressure comprises pumping out liquid cryogen from one chamber and thereafter pressurizing the other chamber to expel cryogen liquid to restore a cryogen liquid level in the one chamber. 13. A method in accordance with claim 1 wherein the cryogen vessel comprises two chambers and reducing pressure comprises pumping out liquid cryogen from a thermally connected pump-down chamber. 14. A method in accordance with claim 1 wherein the cryogen vessel comprises two chambers and reducing pressure comprises pumping out liquid cryogen from a hydraulically connected displacing chamber. 15. A method in accordance with claim 1 wherein the cryogen vessel comprises two chambers and reducing pressure comprises pumping out liquid cryogen from one chamber with a cryogenic pump. 16. A magnetic resonance imaging (MRI) magnet system comprising: a vessel having liquid cryogen therein; anda superconducting magnet within the vessel, wherein the vessel is configured to removably connect to a vacuum pump that is configured to pump cryogen from the vessel to reduce a pressure level within the vessel to a pumped-down pressure level during ramping of the superconducting magnet and increase the pressure level from the pumped-down pressure level to a normal operating pressure level during normal magnet operation after magnet ramping is complete. 17. An MRI magnet system in accordance with claim 16 wherein the vessel comprises a plurality of chambers and further comprising a controller configured to reduce the pressure level by pumping cryogen liquid from one of the chambers such that the other chamber is sub-cooled without reducing a cryogen liquid level. 18. An MRI magnet system in accordance with claim 16 wherein the vessel comprises a plurality of chambers and further comprising a controller configured to reduce the pressure level by pumping out liquid cryogen from one chamber and thereafter pressurizing the other chamber to expel cryogen liquid to restore a cryogen liquid level in the one chamber. 19. An MRI magnet system in accordance with claim 16 wherein the vessel comprises two chambers interconnected with a valve and wherein a pressure level in a smaller chamber of the two chambers is reduced significantly more than a larger chamber of the two chambers. 20. An MRI magnet system in accordance with claim 16 wherein the vessel comprises two chambers interconnected with the vacuum pump. 21. A kit for ramping a magnetic resonance imaging (MRI) magnet system, the kit comprising: a vacuum pump; anda connector configured to connect the vacuum pump to a vessel of the MRI magnet system to pump cryogen from the vessel to reduce a pressure level within the vessel to a pumped-down pressure level during ramping of a superconducting magnet of the MRI magnet system and return the pressure level from the pumped-down pressure level to a normal level after magnet ramping is complete.