Tabletop liquid-helium-free, persistent-mode 1.5-T/70-mm osteoporosis MRI magnet

不到一半的高危美国人接受骨质疏松症筛查，这是一个潜在的衰弱年龄- 代谢驱动的骨质流失导致骨骼脆弱， 骨折的风险。通过以高空间分辨率成像小梁网络微结构， 并测量骨矿物质和骨基质含量，（全三维骨密度， 矿化、皮质厚度、组织形态计量学统计）MRI可能可以表征 骨的完整程度远高于DXA、定量计算机断层扫描（QCT）或 甚至外周微计算机断层扫描，完全避免暴露于电离 辐射当然，MRI通常是一种非常昂贵的技术，需要大量的医院 真实的房地产、基础设施和配套设施。然而，一种新型的超导磁体 基于高温超导体（HTS）二硼化镁，MgB 2， 和固体氮（SN 2），有望成为新一代廉价的MRI磁体， 完全免除使用液氦冷却剂，最近经历了一系列 供应和成本危机，威胁着全球的MRI扫描仪。在这个项目中，我们开发了一个 桌面MgB 2 MRI磁体原型作为这种新磁体技术的演示。的 磁铁，将被集成到一个指骨MRI扫描仪原型，将很容易定位 任何地方，并且可以用于代谢性骨病的普遍筛查。 该项目的具体目标是：1）完成桌面，持续模式，液体- 无氦低温冷却超导（MgB 2）1.5 T/70 mm孔径MRI磁体原型， 用于骨质疏松症研究的指骨扫描; 2）杰罗姆阿克曼博士演示 （Co-I）Martinos中心，MGH，MgB 2/SN 2技术的潜在巨大利益， MR磁体在一个非常紧凑的负担得起的扫描仪的背景下，他将测量3D骨 第5远节指骨的骨密度、骨基质密度和骨小梁显微结构 左手的固态核磁共振成像。创新的磁铁设计概念包括有史以来第一个 高温超导磁体中的持续模式运行与固体夹杂 氮气（SN 2）在冷室中。这些特征导致：1）场强度和时间 稳定性分别比桌面永久性高至少3倍和远好 磁铁，因为虽然这种磁铁在持续模式下运行，永磁体是高度 温度敏感; 2）持续模式磁体操作，标称温度为14 K，持续时间为 制冷机关闭约10小时，为骨质疏松症MRI提供无振动环境 测量;和3）整个单元足够紧凑以放置在桌子上。

Less than half of at-risk Americans are screened for osteoporosis, a potentially debilitating age- associated disease in which metabolically-driven bone loss leads to fragile bones and increased risk of fracture. By imaging the trabecular network microarchitecture at high spatial resolution, and measuring the bone mineral and bone matrix content, (full 3D bone density, degree of mineralization, cortical thickness, histomorphometry statistics) MRI potentially can characterize bone to a far more complete degree than DXA, quantitative computed tomography (QCT), or even peripheral microcomputed tomography, with complete avoidance of exposure to ionizing radiation. MRI of course is generally a very expensive technology requiring extensive hospital real estate, infrastructure and support facilities. However, a novel superconducting magnet technology based on the high-temperature superconductor (HTS) magnesium diboride, MgB2, and solid nitrogen (SN2), promises a new generation of inexpensive MRI magnets which completely dispense with the use of liquid helium coolant that has recently undergone a series of supply and cost crises, threatening MRI scanners worldwide. In this project we develop a tabletop MgB2 MRI magnet prototype as a demonstration of this new magnet technology. The magnet, to be integrated into a phalangeal MRI scanner prototype, will be readily sited anywhere, and which could be used for universal screening for metabolic bone disease. The specific aims of this project are: 1) completion of a tabletop, persistent-mode, liquid- helium-free, cryocooled superconducting (MgB2) 1.5-T/70-mm bore MRI magnet prototype for phalangeal scanning for osteoporosis research; 2) demonstration, by Dr. Jerome Ackerman (Co-I) of the Martinos Center, MGH, of the potentially huge benefits of MgB2/SN2 technology for MR magnets in the context of a very compact affordable scanner—he will measure 3D bone mineral and matrix density and trabecular microstructure of the 5th distal phalanx of the left hand by solid-state MRI. The innovative magnet design concepts include the first-ever persistent-mode operation in high-temperature superconducting magnet and inclusion of solid nitrogen (SN2) in the cold chamber. These features result in: 1) a field strength and temporal stability respectively at least ~3 times greater and far better than that of a tabletop permanent magnet, because while this magnet operates in persistent-mode, permanent magnets are highly temperature sensitive; 2) persistent-mode magnet operation, nominally at 14 K, for a period of ~10 hours with the cryocooler off, provides a vibration-free environment for osteoporosis MRI measurement; and 3) the whole unit is compact enough to be placed on a table.