Polarized Xenon Production: Powerful Narrowed Laser

描述(由申请人提供)：超极化的氙气和氦气在肺功能成像和肺部疾病的量化方面都显示出了实用价值。超极化氙气具有低扩散常数和天然来源可利用性的优点。它在溶解状态成像方面也有应用，在流体和组织中具有很高的溶解度，具有特征的化学位移，揭示了它的微观环境。例如，比较肺部的溶解信号和气体信号，就可以精确地测量表面与体积的比率。一种涉及一套三维肺部图像的方案，或者一个研究人体内灌流器官的溶解相成像的程序，可以有益地利用大量高度极化的氙气。UNH小组已经开发出一种新型的氙气偏振器，它以相对较高的速度和相对较低的压力使气体混合物沿着与激光相反的方向流动，少量产生超过60%的偏振，每小时生产6升产生22%的偏振。这种偏振器的品质因数(偏振乘以生产率)目前比所有其他偏振器技术都高出一个数量级。500托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(在更低的压力下)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比例关系，即在光谱吸收带附近的窄范围内的功率。利用STTRI期资金，我们进一步发展了我们的高功率光谱窄化激光技术，用于自旋交换光泵浦超极化气体。我们把光谱窄的激光技术扩大到了480W。另外，我们改装了5巴130瓦和9巴270瓦激光器来研究两种新技术来降低输出光束的模式结构以获得更好的准直。我们最近在偏振器上安装了270瓦的激光器，我们预计一旦设定好校准，两个激光器的偏振数据就会出现。对于第二阶段，我们将完成减模技术的研究，以获得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振器柱径和两种不同的偏振器柱长，以优化偏振器的物理性能以增加产量。我们希望接近实时超极化产生氙气的目标，在~50%的偏振下，达到60 L/小时。这项研究开发的高功率激光器将提高产生超极化氙气的生产率。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性和组织健康的方法，应用于量化阻塞性肺疾病和肺气肿。目前工作的具体目标是将超极化氙气的产生率提高到60 L/小时以上，允许成像对象实时直接从偏振器呼吸气体。大量、经济高效地生产超极化氙气还将为血液和组织提供一种新的无背景、无循环的造影剂，可能为诊断各种疾病提供独特的对比剂。

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.