Method and apparatus to hyperpolarize materials for enhanced mr techniques

Abstract

An apparatus, system, and method for producing hyperpolarized samples for use in magnetic resonance systems. A sorption pump is incorporated into the apparatus to create a closed system for hyperpolarizing. Being a closed system, the apparatus and system loses no cryogen to atmosphere such that there is no need to replenish cryogen in the system. Under the method, the apparatus is able to operate in three distinct modes.

1 . An apparatus comprising:
 a cooling container containing a cryogenic refrigerant therein, configured to hyperpolarize a plurality of samples therein;   a refrigeration system comprising:
 a refrigerator; and 
 a helium condenser, wherein the helium condenser is separate and positioned exterior to and apart from the cooling container; 
   a sorption pump connected to the cooling container, wherein the sorption pump is separate and spaced apart from the cooling container;   a thermal switch configured to connect and disconnect the refrigeration system from the sorption pump;   a heater disposed adjoining the sorption pump, configured to heat the sorption pump and promote molecular desorption therein;   a single magnetic field producing device in thermal communication with the refrigeration system, wherein the single magnetic field producing device is configured to maintain a selected magnetic field in the apparatus, wherein the single magnet field producing device comprises:
 a superconducting magnet having a bore therethrough positioned about the cooling container; 
 a magnet vessel to enclose the superconducting magnet, the magnet containing liquid cryogen therein to cool the superconducting magnet; and 
 a magnet condenser configured to recondense helium gas that evaporates due to a heat load to the superconducting magnet, 
 wherein the superconducting magnet is configured to produce a primary magnetic field region about the cooling container for hyperpolarization of the plurality of samples and a secondary magnetic field region offset from the primary magnetic field region that extends axially out from the superconducting magnet, 
 wherein the superconducting magnet is further configured to operate without quench or loss of liquid helium when disconnected from the refrigeration system; and 
 at least one thermal bus connecting the refrigeration system, the helium condenser, the magnet condenser, and the thermal switch, 
 further wherein the apparatus comprises a closed system. 
   
     
     
         2 . The apparatus of  claim 1  wherein the superconducting magnet is further configured to operate in proximity to a magnetic resonance (MR) imaging field without degrading a homogeneity thereof. 
     
     
         3 . The apparatus of  claim 1  wherein the sorption pump operates in a sorption mode when the thermal bus is connected to the thermal switch and operates in a desorption mode when the thermal bus is disconnected from the thermal switch. 
     
     
         4 . The apparatus of  claim 3  wherein the sorption pump is configured to reduce pressure in the cooling container and vaporize a portion of the cryogenic refrigerant therein when operating in sorption mode. 
     
     
         5 . The apparatus of  claim 4  wherein the helium condenser is configured to recondense the vaporized cryogenic refrigerant when the sorption pump is operating in desorption mode. 
     
     
         6 . The apparatus of  claim 5  further comprising a pumping line to transfer the vaporized cryogenic refrigerant from the sorption pump to the helium condenser. 
     
     
         7 . The apparatus of  claim 1  wherein the sorption pump further comprises:
 a pump enclosure; 
 a sorbent material housed within the pump enclosure; and 
 cooling fins interspersed within the sorbent material and connected to the thermal switch, wherein the cooling fins cool the sorbent material when the sorption pump is in sorption mode. 
 
     
     
         8 . The apparatus of  claim 1  further comprising a vacuum chamber that encloses the apparatus. 
     
     
         9 . The apparatus of  claim 8  further comprising an ante-chamber attached to the vacuum chamber to maintain a vacuum in the vacuum chamber when loading the substance to be polarized into the cooling chamber. 
     
     
         10 . The apparatus of  claim 1  further comprising:
 a waveguide positioned to transmit microwaves to the substance to be polarized; and 
 a nuclear magnetic resonance (NMR) coil positioned within the cooling container and about the substance to be polarized, wherein the NMR coil is configured to detect a level of polarization of the substance. 
 
     
     
         11 . The apparatus of  claim 1  wherein the cryogenic refrigerant is liquid helium. 
     
     
         12 . The apparatus of  claim 1  wherein the substance to be polarized is  13 C 1 -pyruvate. 
     
     
         13 . A polarizing subsystem comprising:
 a container having a liquid helium bath configured to receive a material to be polarized;   a sorption pump to reduce a pressure in the container, thereby to vaporize a portion of the liquid helium bath, the sorption pump comprising:
 a sorb can configured separate, spaced apart, and exterior to the container; 
   a cooling system comprising:
 a magnet condenser configured separate, spaced apart, and exterior to the container, configured to recondense liquid helium boiled off therefrom and cool the sorption pump and promote molecular adsorption therein; 
   a thermally conductive link that selectively connects the sorption pump and the cooling system to provide selective cooling to the sorption pump;   a heater disposed adjoining the sorption pump, the heater configured to heat the sorption pump and promote molecular desorption therein;   a single magnetic field producing device configured to maintain a selected magnetic field for polarizing the material in the apparatus, wherein the single magnetic field producing device is cooled by the cooling system,   wherein the polarizer system operates in a closed cyclical thermal cycle alternating between a polarizing phase and a reheating phase based on the thermally conductive link of the sorption pump to the cooling system.   
     
     
         14 . The polarizer system of  claim 13  further comprising a thermal switch to connect and disconnect the thermally conductive link from the sorption pump. 
     
     
         15 . The polarizer system of  claim 14  wherein the thermal switch connects the thermally conductive link to the sorption pump during the polarizing phase and disconnects the thermally conductive link from the sorption pump during the reheating phase. 
     
     
         16 . The polarizer system of  claim 13  further comprising a helium condenser to recondense the vaporized helium when the polarizer system is in the reheating phase. 
     
     
         17 . The polarizer system of  claim 13  wherein the cooling system is configured as a closed cycle refrigerator to produce cryogenic temperatures. 
     
     
         18 . A method for producing a hyperpolarized material comprising:
 placing a material sample in a vessel containing a liquid helium bath;   reducing a temperature of the liquid helium bath with a sorption pump and a refrigeration system, wherein the sorption pump comprises:
 a sorb can configured separate from and exterior to and spaced apart from the vessel, 
 wherein the refrigeration system comprises: 
 a helium condenser configured separate from and exterior to and spaced apart from the vessel; 
   refilling the liquid helium bath by heating the sorption pump with a heater, the heater being disposed adjoining the sorption pump;   positioning a single magnetic field producing device adjacent the vessel, wherein the single magnetic field producing device is configured to product a high homogeneity magnetic field and a fringe magnetic field offset from the high homogeneity field; and   polarizing the material sample when the liquid helium bath has been sufficiently cooled by the single magnetic field producing device.   
     
     
         19 . The method of  claim 18  wherein reducing a temperature further comprises:
 lowering a pressure in the vessel by way of the sorption pump; and 
 vaporizing a portion of the liquid helium bath at the lowered pressure. 
 
     
     
         20 . The method of  claim 19  further comprising recondensing the vaporized helium by way of a magnet condenser to refill the vessel with liquid helium. 
     
     
         21 . A polarizer system comprising:
 a refrigerator;   a magnet condenser;   a helium condenser;   a thermal bus permanently linking the refrigerator, the magnet condenser, and the helium condenser;   a sorption pump selectively linked through a thermal switch to the thermal bus;   a heater adjoining the sorption pump;   a container containing a cryogenic refrigerant therein, configured to receive a plurality of samples for polarizing therein;   a magnetic field producing device in a magnet vessel surrounding the container;   wherein the polarizing system is further configured to operate in three separate modes, wherein:   a first mode comprises:
 heating the sorption pump with the heater, thereby releasing helium gas to be cooled and liquefied by the helium condenser, wherein the released helium gas heats the thermal bus, thereby isolating the magnet vessel due to a thermal diode effect at the magnet condenser; 
   a second mode comprises:
 upon completion of condensation of helium from the sorption pump, turning off the heater and cooling the sorption pump by closing the thermal switch, thereby creating a thermal linkage of the sorption pump, the thermal bus and the refrigerator, and thermally isolating the magnetic field producing device from the thermal bus; and, 
   a third mode comprises:
 cooling the magnetic field producing device, thereby eliminating a thermal diode effect of the magnet condenser.