Polarized Xenon Production: Powerful Narrowed Laser

描述（由申请人提供）：超偏光氙气和氦气在肺功能成像和肺部疾病量化方面都有应用。超极化氙具有低扩散常数和天然来源的优点。它在溶解状态成像中也有应用，在流体和组织中具有高溶解度，并且具有典型的化学位移，可以揭示其微观环境。例如，肺中溶解信号和气体信号的比较，提供了表面体积比的精确测量。一套三维肺成像方案或一个研究人体灌注器官溶解相成像的程序可以有效地利用大量高偏振氙气。UNH集团开发了一种新型的氙气偏振器，该偏振器以相对高的速度和低压沿与激光束相反的方向流动气体混合物，在少量时产生超过60%的偏振，在生产速度为每小时6升时产生22%的偏振。该偏振器的性能指标（偏振倍生产率）目前超过所有其他偏振器技术一个数量级。500 torr的工作压力代表了更高的激光吸收（在更高的压力下）和更快的自旋交换速率（在较低的压力下）之间的折衷。我们的数值模拟表明，磁化输出与吸收激光功率成正比，即在光谱吸收带附近的一个狭窄范围内的功率。利用STTR第一期资金，我们进一步开发了用于超极化气体自旋交换光泵浦的高功率频谱狭窄激光技术。我们将窄光谱激光技术提升到480瓦。另外，我们调整了我们的5 bar 130瓦和9 bar 270瓦激光器，研究了两种新技术，以减少输出光束的模式结构，以获得更好的准直。我们最近在偏光镜上安装了270瓦的激光器，一旦校准完成，我们期望两种激光器的偏振数据。在第二阶段，我们将完成模式缩减技术的研究，以实现具有接近理想准直的窄光谱输出。我们将测量激光输出作为模式和光谱约束的函数。我们将研究偏振器输出作为激光功率的函数。我们将测试两种不同的偏光柱直径和两种不同的偏光柱长度，以优化偏光柱的物理性能，以增加输出。我们希望接近实时超极化氙生产的目标，在~50%极化下达到60 L/hr。本研究开发的高功率激光器将提高超偏振氙的生产速率。超极化氙气磁共振成像（MRI）最近被证明是一种非常敏感的评估肺通气和组织健康的方法，可用于量化阻塞性肺疾病和肺气肿。当前工作的具体目标是将超偏振氙气的生产速率提高到大于60升/小时，使成像对象能够实时直接从偏振器中呼吸气体。高容量、高成本效益的超极化氙气生产也将为血液和组织提供一种新的无背景、非循环造影剂，可为广泛疾病的诊断提供独特的造影剂。

DESCRIPTION (provided by applicant): Hyperpolarized xenon and helium have both demonstrated utility in functional lung imaging and quantifying lung disease. Hyperpolarized xenon offers advantages of a low diffusion constant and availability from natural sources. It also has applications in dissolved state imaging, with a high solubility in fluids and tissues and a characteristic chemical shift, revealing its microscopic environment. Comparison of the dissolved and gaseous signals in lungs, for example, offers a precise measure of surface-to-volume ratio. A protocol involving a suite of lung images in three-dimensions or a program to investigate dissolved- phase imaging of perfused organs in humans could beneficially utilize large quantities of highly polarized xenon. The UNH group has developed a new type of xenon polarizer that flows the gas mixture at relatively high velocity and low pressure along a direction opposite to the laser beam, producing polarization of over 60% for small quantities and 22% for a production rate of six liters per hour. The figure-of-merit (polarization times production rate) of this polarizer presently exceeds all other polarizer technologies by an order of magnitude. The 500 torr operating pressure represents a compromise between higher laser absorption (at higher pressure) and faster spin-exchange rates (at lower pressure). Our numerical simulations indicate that magnetization output scales with absorbed laser power, that is, power within a narrow range around the spectral absorption band. Using STTR Phase I funding we have further developed our high-power spectrally narrowed laser technology for spin-exchange optical pumping of hyperpolarized gas. We scaled up our spectrally narrowed laser technology to 480W. Separately, we adapted our 5 bar 130 watt and 9 bar 270 watt lasers to investigate two new technologies to reduce the mode structure of the output beam for better collimation. We recently installed our 270 watt laser on the polarizer, and we expect polarization figures for both lasers once calibrations are set. For Phase II we will complete our study of the mode reduction technology to achieve a narrow spectral output with nearly ideal collimation. We will measure laser output as a function of mode and spectral constraints. We will investigate polarizer output as a function of laser power. We will test two different polarizer column diameters and two different polarizer column lengths to optimize the physical properties of the polarizer for increased output. We expect to come close to the goal of real-time hyperpolarized xenon production, 60 L/hr at ~50% polarization. This research to develop a high power laser will increase the production rate for producing hyperpolarized xenon. Hyperpolarized Xenon Magnetic Resonance Imaging (MRI) was recently demonstrated as an exquisitely sensitive method for assessment of lung ventilation and tissue health, with applications to quantifying obstructive lung disease and emphysema. The specific aim of the current work is to increase the production rate of hyperpolarized xenon to greater than 60 L/hr, allowing an imaging subject to breathe the gas directly from the polarizer in real time. High-volume, cost-effective production of hyperpolarized xenon will also provide a new background-free, non-recirculating contrast agent for blood and tissues which may offer unique contrast for diagnosing a broad spectrum of diseases.