The cooling of high-field superconducting magnets adds and additional component to the operating cost of MRI: the cost of replenishing the liquid helium cryogen that is continuously lost to boil-off. Chesapeake Cryogenics proposes to construct a recondenser that will liquefy helium gas, enabling its re-use, and thereby lowering the total operating cost of MRI. The recondenser is based on a new, patented refrigeration scheme called the BOREAS cycle. Its advantages include low vibration, the capability to move much of the mechanism up to 60 feet from the MRI unit, and lower power usage than other refrigerator types. Depending on the MRI model, the proposed recondenser will reduce the necessary frequency of liquid helium replenishment, or eliminate it entirely. A test of prototype BOREAS recondenser on a commercial MRI unit has reduced liquid helium biol-off by a factor of five times. Optimization of the recondenser will achieve still better performance. In the Phase I project Chesapeake Cryogenics will establish the feasibility of the optimized recondenser through design and simulation of the recondenser performance. In Phase II Chesapeake Cryogenics will construct the complete optimized recondenser and demonstrate its performance on a commercial MRI unit.
The proposed liquid helium recondenser will lower the operating cost of high-field MRI. It will also enable new MRI systems that employ superconducting magnets, but do not require the replenishment of any cryogens.
