Simultaneous Xe129 MRI of Regional Lung Ventilation and Gas Uptake in COPD

描述(申请人提供)：慢性阻塞性肺疾病(COPD)是美国第四大死因，也是近年来年龄调整死亡率上升的唯一主要死因。随着对COPD相关遗传和分子途径的了解不断深入，人们越来越需要改进的工具来表征肺功能，如将基因亚型与表型表达相结合，监测对新治疗的功能反应，或帮助快速开发新的呼吸系统药物。然而，尽管医学成像技术取得了许多进步，但要以一种适合于人类常规应用的方式，在体内对肺的最基本生理功能--向空气空间的气体输送以及肺实质和血液的气体吸收--进行区域性描述和量化仍然具有挑战性。为了解决这一未得到满足的需求，该项目利用了我们团队最近开发的一种方法，该方法基于超极化氙气-129(ThXe129)的磁共振成像(MRI)，允许同时观察换气(气体输送)和气体吸收的3D分布，以及基于相关换气的区域气体吸收的量化，适用于呼吸功能受损的受试者的单一短暂屏气采集。该项目的第一个目标是实施并在人体中验证这项技术的关键改进，包括在图像中分别描述溶解在红细胞中的hthXe129部分和溶解在肺实质/血浆中的部分。第二个目标是通过测量作为测量参数和健康受试者肺充气的函数的信号行为来表征健康肺中的气体摄取，如溶解的thXe129信号所反映的，然后基于信号行为数据得出测量相关气体摄取的相关3D分布的优化方案。这些优化的方案将在患有轻度和重度COPD的受试者中得到验证。第三个也是最后一个目标是在20名健康对照组、10名肺活量正常的吸烟者和30名COPD患者中进行一项探索性研究，范围从Gold 1级到3级，以作为疾病严重程度的函数，表征溶解在红细胞和肺实质/血浆中的标准化气体摄取分布以及溶解在红细胞和肺实质/血浆中的部分。这些气体摄取结果将与标准的胸部和肺功能计算机断层扫描(CT)结果进行比较。拟议项目的成功完成将带来一种改进的、优化的方法，用于同时进行通风和气体吸收的磁共振成像，提供标准化的区域气体吸收值，可以在受试者之间进行定量比较。这项技术提供了有关肺的重要功能信息，这是任何现有的临床影像设备所无法提供的，并且具有提供关于COPD的独特的、生理上相关的和临床上重要的信息的巨大潜力。

DESCRIPTION (provided by applicant): Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death in the United States and is the only major cause of death for which the age-adjusted death rate has increased in recent years. As progress is made in understanding the genetic and molecular pathways involved in COPD, there is a growing need for improved tools to characterize lung function for applications such as coupling genetic subtypes to phenotype expression, monitoring functional response to new treatments, or aiding in the rapid development of novel respiratory drugs. Nonetheless, despite a myriad of technical advances in medical imaging, it remains challenging to obtain in-vivo regional depiction and quantification of the most basic physiological functions of the lung - gas delivery to the airspaces and gas uptake by the lung parenchyma and blood - in a manner suitable for routine application in humans. To address this unmet need, this project takes advantage of a method recently developed by our group, based on magnetic resonance imaging (MRI) of hyperpolarized xenon-129 (hypXe129), that permits simultaneous observation of the 3D distributions of ventilation (gas delivery) and gas uptake, as well as quantification of regional gas uptake based on the associated ventilation, from a single short breath-hold acquisition suitable for subjects with compromised respiratory function. The first aim of this project is to implement, and validate in human subjects, key improvements to this technique, including the ability to separately depict in the images the fraction of hypXe129 dissolved in red blood cells and that dissolved in lung parenchyma/plasma. The second aim is to characterize gas uptake in the healthy lung, as reflected by dissolved-hypXe129 signals, by measuring signal behaviors as a function of measurement parameters and lung inflation in healthy subjects, and then derive optimized protocols, based on the signal-behavior data, for measuring the associated 3D distributions of gas uptake. These optimized protocols will be validated in subjects with mild and severe COPD. The third and final aim is to perform an exploratory study in 20 healthy control subjects, 10 smokers with normal spirometry and 30 subjects with COPD, ranging from GOLD stage 1 to 3, to characterize, as a function of disease severity, the normalized gas- uptake distributions for dissolved hypXe129 and for the fractions of hypXe129 dissolved in red blood cells and lung parenchyma/plasma. These gas-uptake results will be compared to results from standard computed tomography (CT) of the chest and pulmonary function testing. Successful completion of the proposed project will result in an improved, optimized version of the method for simultaneous MR imaging of ventilation and gas uptake that provides normalized regional gas-uptake values, which can be quantitatively compared among subjects. This technique offers important functional information about the lung, which is not available from any existing clinical imaging modality, and has substantial potential to provide unique, physiologically relevant, and clinically important information about COPD.