VERY LOW FIELD HYPERPOLARIZED NOBLE GAS MRI

描述(改编自申请者的摘要)：极低磁场(VLF) 使用超极化(3)He和(129)Xe的信号的磁共振成像系统将是 开发的目的是为了研究人类的肺部，并探索其潜力 用于检测和分期的低成本、便携式诊断工具 肺部疾病。(3)He和(129)Xe的自旋1/2核可以是 超极化到其热平衡值的105倍 与Rb原子的自旋交换碰撞 圆偏振光完全变成一个电子的自旋态。极大的 来自这种超极化物种的增强信号强到足以允许 对它们所占空间的高速成像，使它们成为吸引人的磁共振探测器。 在过去的四年里，这一领域有了很大的发展，因为PI和 合作者通过获取核磁共振图像发明了超极化惰性气体核磁共振 被超极化(129)Xe充气的切除的小鼠肺。 改进的肺气-空间成像已被证明使用来自 超极化(3)He和(129)Xe。有了后者，就有了希望 对通风和灌流进行研究，因为它在 血液和组织。特别重要的是，在 超极化稀有气体核磁共振，在甚低频。甚低频磁共振成像变得可行，因为 原子核的偏振水平由超极化过程设置， 并且与静磁场B(O)无关。信号强度 因此，标度为B(O)而不是常规MRI的B(O)(2)。这个 然后，SNR实际上在很大范围内独立于场，并且 低场强并不是一个劣势。 可以产生大约100-200高斯(0.01-0.02T)的极低磁场 低成本的轻便螺线管。因此，甚低频惰性气体MRI可能导致 价格低廉的便携式成像系统。超低频磁共振成像系统的研制 建议使用定制的100-200高斯的阻性磁铁。渐变、垫片、 射频线圈将被开发并连接到商业低频 核磁共振控制台。0.5毫米量级的空间分辨率计划在 视野大小为30厘米，相当于人类肺部的典型大小。自样品以来 在VLF，高温超导的噪声主要是线圈噪声 将开发高温超导(HTS)线圈，以提高信噪比和面内分辨率。脉搏 序列将设计用于非常低场的捕获，并在 才能利用巨大但不可再生的超极化 这是超极化稀有气体磁共振成像的特点。 将进行初步的人体肺部成像研究。长期的 目标是开发一种低成本的便携式单元，可以用于 在各种诊所、医生办公室和疗养院进行肺部筛查， 甚至可能用于微重力条件下的空间肺功能研究 环境。

DESCRIPTION (Adapted from the applicant's abstract): A very low-field (VLF) MRI system employing the signal from hyperpolarized (3)He and (129)Xe will be developed in order to investigate the human lung, and to explore the potential for a low-cost, portable diagnostic tool for the detection and staging of pulmonary diseases. The spin-1/2 nuclei of (3)He and (129)Xe can be "hyperpolarized" to 105 times their thermal equilibrium value spin-exchange collisions with Rb atoms that have been "optically pumped" by circularly polarized light entirely into one electron spin state. The vastly enhanced signal from such hyperpolarized species is strong enough to permit high speed imaging of the space they occupy, making them intriguing MR probes. The field has developed considerably in the past four years, since the PI and collaborators invented hyperpolarized noble gas MRI by acquiring MR images of an excised mouse lung that had been inflated with hyperpolarized (129)Xe. Improved lung gas-space imaging has been demonstrated using the signal from both hyperpolarized (3)He and (129)Xe. With the latter, there is the promise of investigating both ventilation and perfusion since it is highly soluble in blood and tissues. Of special importance is the high SNR achievable in hyperpolarized noble gas MRI, at VLF. VLF MRI becomes feasible since the level of polarization of the nuclei is set by the hyperpolarization process, and is independent of the static magnetic field, B(o). The signal strength therefore scales as B(o) rather than as the B(o)(2) of conventional MRI. The SNR then becomes virtually independent of the field over a great range, and low field strength is not a disadvantage. Very low-fields of about 100-200 Gauss (0.01-0.02 T) can be produced by lightweight solenoids at low-cost. Therefore, VLF noble gas MRI may lead to inexpensive, portable imaging systems. The development of a VLF MRI system is proposed using custom-made resistive magnet of 100-200 Gauss. Gradient, shim, and RF coils will be developed and interfaced to a commercial low frequency MRI console. A spatial resolution on the order of 0.5 mm is planned over a field of view of 30 cm DSV, the typical size of human lungs. Since sample noise is dominated by coil noise at VLF, high temperature superconducting (HTS) coils will be developed to improve SNR and in-plane resolution. Pulse sequences will be designed for very low-field acquisition and optimized in order to take advantage of the large, but non-renewable hyperpolarized magnetization that is characteristic of hyperpolarized noble gas MRI. Preliminary human lung imaging studies will be conducted. A long term objective is the development of a low-cost portable unit that can be used for lung screening in a variety of clinics, physician's offices and nursing homes, and perhaps even for space based pulmonary function research in microgravity environments.