Conductors, joints, and Coils for Cryogen Free Whole Body 3 T MRI systems

描述(申请人提供)：目前安装的全身核磁共振系统大多基于1.5T液氦冷却NbTi磁体，但3.0T系统的安装率正在迅速增加。然而，氦成本的增加是有据可查的，这会导致磁共振成像系统生命周期成本的增加，这可能会限制传统患者群体的现成使用，并限制将可用性扩大到传统上服务较差的患者群体的能力。这个问题的根本原因是世界范围内氦的日益短缺。主要的MRI磁体制造商(西门子、GE和Phillips)都有专注于将1.5T螺线管线圈从液氦浴冷却转换为干式(无制冷剂)传导冷却的开发计划。事实上，不需要液氦冷却(即无制冷剂、传导冷却的操作)正变得越来越重要。目前，磁共振成像系统(2000-3000升)在美国发货前在工厂装满液体氦，成本约为20-30K。考虑到从2006年到2011年，LHe的成本增加了两倍，预计还会继续增加，因此液体氦磁共振设备的成本相应增加是可以预期的。在世界上一些地区，这种液体的价格约为每升9-13美元，在另一些地区，价格约为每升25-70美元，根据核磁共振的大小和位置，重新灌装的成本为1.8万美元至21万美元。因此，据预测，对不依赖液体氦冷却的磁共振磁体的需求将不断增长。即使在磁共振成像的液体制冷剂问题之外，低温冷却磁共振磁体的开发也可能允许新的几何结构和磁共振应用，开辟新的治疗可能性。然而，我们必须把重点放在该行业能够将这项新技术商业化的地方。因此，拟议的计划侧重于开发技术，以实现使用低温冷却模式的无制冷剂3T系统。我们建议通过以下方式做到这一点：(1)在适用于3T MRI(4-10K，0-4T)的磁场和温度范围内，在当前开发的1G导线上将实际的MgB2工程电流密度Je增加一个数量级，(2)在(1)的复丝2G导线中开发足以持续模式磁体操作(在相关磁场范围内30或更多)的n值，(3)开发具有足够细节的磁体模型以制定导体规格/目标，以及冷却、线圈段上的温度梯度和导体性能之间的权衡，(4)确定适合沟道内导线的铜/Sc比，并演示其长距离制造；(5)使用第(4)项中的WIC演示总线圈的一段，具有所需的电流、n值、温度梯度和失超性能；以及(6)在磁体工程友好的反应和风力模式下开发用于镁B2导体的坚固的永久接头。

DESCRIPTION (provided by applicant): Most presently installed full-body MRI systems are based on 1.5 T liquid-He- cooled NbTi magnets, but the rate of installation of 3.0 T systems is rapidly increasing. However, the increasing cost of helium is well documented, and this leads to increases in the life cycle cost of MRI systems, which could limit ready access for traditional patient groups, and limit the ability to expand availability to traditionally less well served patint groups. The root cause of the problem is the growing shortage of helium worldwide. The major MRI magnet manufacturers (Siemens, GE, and Phillips) each have development programs focused on converting the 1.5T solenoid coils from liquid helium bath cooling to dry (cryogen free) conduction cooling. Indeed, freedom from the need for liquid-helium cooling (i.e. cryogen free, conduction-cooled, operation) is becoming more and more important. Presently, MRI systems (2000-3000 liters) are filled with liquid He helium at the factory prior to shipping at a cost in the U.S. of about 20-30 K. Given that from 2006 to 2011 the cost of LHe has tripled, and it is expected to continue to increase, corresponding increases in the cost of liquid-He MRI units can be expected. In some parts of the world liquid He costs about $9-13 per liter and in others about $25 to $70 per liter leading to re-filling costs of $18,000-$210,000 depending on the MRI's size and location. Thus a growing demand is predicted for MRI magnets that do not depend on liquid He for cooling. Even beyond the liquid cryogen issues for MRI, the development of cryocooled MRI magnets could allow for new geometries and MRI applications, opening up new treatment possibilities. However, we must focus where the industry can transition this new technology commercially. Accordingly, the proposed program focuses on developing the technology to enable cryogen free 3 T systems using a cryocooled mode. We proposed to do this by; (1) Increases practical MgB2 engineering current density, Je, by one order of magnitude over presently developed 1 G wire, in the fields and temperature ranges appropriate to 3 T MRI (4-10 K, 0-4 T), (2) Developing n-values sufficient for persistent mode magnet operation (30 or more in the relevant field range) in the multifilament 2 G wires of (1), (3) Developing a magnet model with sufficient detail to develop the conductor specification/targets, and the tradeoffs between cooling, temperature gradients across a coil segment, and conductor performance, (4) Determining the proper Cu/SC ratio for wire-in-channel MgB2/Cu, and demonstrate its long-length manufacture, (5) Demonstrating one segment of the total coil, using the WIC of item (4), with the needed current, n-value, temperature gradient, and quench performance, and (6) Developing a robust persistent joint for MgB2 conductors in a magnet engineering friendly react & wind mode.