Polarized Xenon Production: Powerful Narrowed Laser

描述（由申请人提供）：超极化氙和氦均已证明可用于功能性肺成像和肺部疾病定量。超极化氙具有低扩散常数和可从天然来源获得的优点。它还可用于溶解态成像，在液体和组织中具有高溶解度，并具有特征化学位移，可揭示其微观环境。例如，比较肺部的溶解信号和气体信号，可以精确测量表面积与体积比。涉及一套三维肺部图像的协议或研究人体灌注器官的溶解相成像的程序可以有利地利用大量的高度极化的氙。UNH小组开发了一种新型的氙偏振器，该偏振器使气体混合物以相对较高的速度和较低的压力沿着与激光束相反的方向流动，在小批量生产时产生超过60%的偏振，在每小时6升的生产率下产生22%的偏振。该偏振器的品质因数（偏振乘以生产率）目前超过所有其他偏振器技术一个数量级。500埃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，磁化输出与吸收的激光功率，即在光谱吸收带附近的一个狭窄的范围内的功率的比例。利用STTR第一阶段的资金，我们进一步开发了我们的高功率光谱窄激光技术，用于超极化气体的自旋交换光泵浦。我们将光谱窄化激光技术扩展到480 W。另外，我们调整了我们的5巴130瓦和9巴270瓦激光器，以研究两种新技术，以减少输出光束的模式结构，以获得更好的准直。我们最近在偏振器上安装了270瓦的激光器，一旦校准完成，我们预计两个激光器的偏振值都将达到。对于第二阶段，我们将完成我们的研究模式减少技术，以实现一个狭窄的光谱输出与接近理想的准直。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直径和两种不同的偏振器柱长度，以优化偏振器的物理特性，从而提高输出。我们期望接近实时超极化氙生产的目标，在~50%极化下为60 L/hr。本研究发展高功率雷射，将提高超极化氙的产生率。最近，超极化氙磁共振成像（MRI）被证明是评估肺通气和组织健康的一种极其灵敏的方法，可应用于量化阻塞性肺病和肺气肿。当前工作的具体目标是将超极化氙的产生速率增加到大于60 L/hr，允许成像主体真实的时间直接从偏振器呼吸气体。高容量、高成本效益的超极化氙生产还将为血液和组织提供一种新的无背景、非再循环造影剂，可为诊断广谱疾病提供独特的造影剂。

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.