Infrastructure and Applications of Hyperpolarized 129Xe

描述(由申请人提供)： 近年来，3He超极化气体磁共振成像领域取得了很大的进展。使用129Xe气体的核磁共振则不是这样。造成这种差异的主要原因是可用于研究的高极化129Xe气体供应有限。例如，目前用于129Xe磁共振成像的偏振设备通常在10%的偏振下每小时提供不到1/2升。我们合作的成员最近展示了一种革命性的新极化设备，与现有最先进的设备相比，该设备在更低的氙压和更高的流速下运行。他们的结果证实，在较低的工作压力和固定的产气率下，可以获得更高的氙极化。因此，BRP的目的是利用这种令人兴奋的高极化和高通量]29Xe气体来探索其提供肺结构和功能的定量信息的潜力。虽然129Xe和3He都提供了出色的通气图，但129Xe在三个方面是独一无二的：(1)组织中的高溶解度，(2)组织相对于气体核磁共振频率的较大化学位移，以及(3)扩散常数比3He小25倍。特性1和特性2允许测量氙气进入组织的交换。我们将利用这一点来确定区域表面积与体积比，这是一个与气体交换效率密切相关的微观参数。第二个量，即129Xe气体在腺泡中的扩散系数，也将作为扩散演化所允许的时间的函数来测量。由于特性3,129Xe的短时间扩散距离小于3He的可能扩散距离，探测尺寸与平均肺泡孔大小相当。在很长一段时间内，D(T)提供了关于肺微结构的附加信息，特别是相邻腺泡结构之间的连通性(或曲折性)。曲折性可能是空气颗粒物易感性的一个重要预测因素。我们建议测量129Xe D(T)以确定其作为肺微结构“指纹”的价值。为这一提议而组建的研究团队已经密切合作了6年多，并在极化和利用129Xe的独特功能方面开发了特殊的专业知识。一个偏光镜将在布里格姆妇女医院建造、安装和支持。动物和人体实验旨在证明129Xe磁共振成像可以提供的结构和功能信息。

DESCRIPTION (provided by applicant): The field of 3He hyperpolarized gas MRI has seen great advances recently. This is not the case for MRI with 129Xe gas. The principal reason for this disparity is the limited supply of highly polarized 129Xe gas available for studies. For example, present day polarization apparatus for 129Xe MRI typically provide less than 1/2 liter per hour at 10% polarization. Members of our collaboration have recently demonstrated a revolutionary new polarization apparatus that operates at lower xenon pressures and higher flow velocities than existing state-of-the-art. Their results have confirmed that higher xenon polarizations can be obtained at lower operating pressures with fixed gas production rate. Thus the purpose of this BRP is to use this exciting new source of highly polarized and high throughput ]29Xe gas to explore its potential to provide quantitative information on lung structure and function. While both 129Xe and 3He provide excellent ventilation maps, 129Xe is unique in 3 ways: (1) a high solubililty in tissue, (2) a large chemical shift of the tissue relative to the gas NMR frequency, and (3) a -25 times smaller diffusion constant compared to 3He. Properties 1 and 2 permit measurement of exchange of xenon gas into tissue. We will exploit this to determine the regional surface area to volume ratio, a microstructure parameter closely related to gas exchange efficiency. A second quantity, the diffusivity of 129Xe gas in the acinus, will also be measured as a function of the time allowed for diffusion to evolve. Because of Property 3, the short time 129Xe diffusion distance is smaller than possible with 3He, probing dimensions comparable to the average alveolar pore size. At long times, D(t) gives additional information about the lung microstructure, specifically the connectivity (or tortuosity) between adjacent acinar structures. Tortuosity may be an important predictor for susceptibility to airborne particulates. We propose measurements of 129Xe D(t) to establish its value as a "fingerprint" of lung microstructure. The team of researchers assembled for this proposal have been closely collaborating for over 6 years and have developed particular expertise in both polarizing and exploiting the unique features of 129Xe. A polarizer will be built, sited and supported at Brigham and Women's Hospital. Animal and human studies are proposed to demonstrate the structural and functional information 129Xe MRI can provide.