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

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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.