For 7 tesla full body MRI bore magnet systems, NbTi superconductor wire has reached its limit at 4 K. Above 7T if NbTi is used it requires super cooling of helium to 1.8-2.4 K to achieve 7-11T bore MRI and NMR systems. All these 7T full body MRI background magnets sold by Siemens, Philips, and GE have been manufactured by Aligent (formerly known at Varian before that Magnex). Aligent recently announced that they will no longer accept orders for these 7T magnets and sited costs and availability of helium. Some MRI manufacturers have stopped accepting new order for 7T MRIs because of delivery issues and helium shortages. The medical community would like to see 7T MRI's become a clinical system. Hence, the price needs to come down dramatically and in the long run the only real solution is to have conduction cooled magnets to take the helium shortage issue out of the equation. Nb3Sn superconductor wire is the ideal candidate for these applications due to its higher current density at higher field like 10-16T. Plus, the transition temperature (Tc) is higher 17K for Nb3Sn vs. 9K for NbTi. When a large NbTi magnet is cooled in a liquid helium bath, the temperature differential in the coil needs to be less than 1K. At 7K Nb3Sn still retains over 1/2 its engineering current density to enable the design of 7-12T magnetic fields in the bore of large magnets, and it provides the 2-3K margin to enable conduction cooling and can eliminate the need for liquid helium bath cooling. This eliminates the need for 4000-6000 liters of helium every time the magnet needs to be cooled down (training the magnet in the factory, setting up the magnet at the hospital, and when the magnet quenches several times over its useful life cycle of 7-10 years). What enables our specific aim of large conduction cooled Nb3Sn magnets for medical applications is that Hyper Tech has developed a low cost and high performance tube type Nb3Sn superconductor which is an excellent wire candidate to open up this market. With the increase in performance it can economically enable conduction cooled magnets and eliminate the helium batch cooling. This new, Hyper Tech, lower cost, high performance (Jc of 2000A/mm2 at 4.2K-12T) Nb3Sn superconductor wire could cut the wire cost -compared to NbTi wire for a 7 Tesla full body MRI. It would dramatically decrease the magnet weight and size. It will also make the conduction cooling possible for the 4-7K range. During this Fast Track Phase I and Phase II project we will demonstrate that a new low cost Nb3Sn superconductor developed by Hyper Tech can be used to fabricate large conduction cooled 50-100 cm bore coils for 7T tesla MRI and NMR systems. This will benefit the public for MRI and NMR applications that require high resolution and rapid imaging. This matches NIH's mission of delivering cost effective improved health care to the public.
Hyper Tech will conduct research and development on conduction cooled large bore 7T plus Nb3Sn superconducting magnets for MRI, NMR, and Medical Particle Accelerators. The development of these large conduction cooled magnets will enable these markets to avoid the predicted helium shortage by eliminating helium bath cooling for these magnets. In addition, the magnet systems will, lower cost, be safer and less prone to quenching than presently used NbTi or Nb3Sn helium bath cooled superconducting magnet systems.
