Microscopic MRI with Joule-Thomson Micro-Refrigerators

0071837 Wright磁共振显微成像（u-MRI）由于其非破坏性、非侵入性的性质和丰富多样的可用对比机制，已经成为材料微观表征的宝贵工具，尽管许多用于产生对比的技术受到低信噪比（SNR）的影响。 然而，近年来的技术创新是使用高Tc超导体（HTS）材料来构造具有极高保真度的射频（RF）检测器线圈，以大大增加生物组织的u-MRI中的SNR。 虽然低温冷却RF线圈的回报可能是巨大的，如最近对于由铜制成的常规线圈所证明的，线圈通常被冷却到约40 K，并且必须保持紧邻被成像的（体温）组织。 因此，它们的实施对现有的低温技术提出了重大挑战，目前的解决方案引起了对液体冷冻剂危害的关注。 然而，最近，已经开发出一种新型的两级焦耳-汤姆逊微型制冷机，能够在35 K下持续工作。 这项工作提出了一种新的方法，低温探头的设计，适用于线圈从传统和高温超导材料，涉及精密冷却，通过这种微型焦耳-汤姆逊制冷机。 这种新的方法进行探索和开发，代表了一个重大的变化，在现有的技术重要的u-MRI，以及创新的低温工程具体到这一领域，很可能有广泛的影响，生物医学研究。 它还包含一个风险因素，因为它寻求应用新型焦耳-汤姆森微型制冷技术来推进u-MRI低温学的新兴子领域，然而，它有潜力接纳成像和光谱技术，以前排除了由信噪比的限制。微型冷冻探针将在这项工作中开发的应用，作为新的工具，u-MRI和核磁共振（NMR）正常和病理组织以及具有医学意义的生物结构的光谱学。 应用可能包括骨小梁结构和脊髓损伤的体内成像，小鼠大脑的体外成像，以及生物相关细胞和液体的体外高场NMR光谱。 据设想，这样的工具将允许更准确的定量分析组织的微观结构和组成，影响的理解，诊断和治疗代谢性骨疾病，脊髓损伤和修复，在发育中的大脑中的基因表达，和癌症。

0071837WrightMagnetic resonance micro-imaging (u-MRI) has become an invaluable tool for the microscopic characterization of materials due to its non-destructive, non-invasive nature and the rich variety of available contrast mechanisms, although many of the techniques for generating contrast suffer from low signal-to-noise ratio (SNR). A technological innovation of recent years, however, has been the use of high-Tc superconductor (HTS) materials to construct radio frequency (RF) detector coils of extremely high fidelity for greatly increased SNR in u-MRI of biological tissues. While the rewards of cryogenically cooling the RF coil can be great, as recently demonstrated for conventional coils made of copper, the coils are typically cooled to about 40 K and must be maintained in close proximity to the (body-temperature) tissue being imaged. Their implementation thus has posed significant challenges to existing cryogenic technology, with current solutions raising concern over the hazards of liquid cryogens. Very recently, however, a new type of two-stage Joule-Thomson micro-refrigerator has been developed, capable of sustained operation at 35 K. This work proposes a new approach to cryogenic probe design, applicable to coils made from both conventional and HTS materials, that involves precision cooling by means of such micro-miniature Joule-Thomson refrigerators. This new approach to be explored and developed represents a substantial change in the existing technology important to u-MRI as well as an innovation in cryogenic engineering specific to this field and is likely to have broad implications for biomedical research. It also contains an element of risk in that it seeks to apply novel Joule-Thomson micro-refrigeration technology to advance the emerging sub-field of u-MRI cryogenics, yet it has potential to admit imaging and spectroscopy techniques previously precluded by the limits of SNR.The micro-cryo-probes to be developed in this work will have application as new tools for u-MRI and nuclear magnetic resonance (NMR) spectroscopy of normal and pathological tissues and biological structures of medical significance. Applications may include in vivo imaging of trabecular bone structure and spinal cord injuries, ex vivo imaging of the mouse brain, and in vitro high-field NMR spectroscopy of biologically relevant cells and fluids. It is envisioned that such tools will permit more accurate quantitative analyses of tissue microstructure and composition, with impact on the understanding, diagnosis and treatment of metabolic bone diseases, spinal cord injury and repair, genetic expression in the developing brain, and cancer.