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

描述（由申请人提供）：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增加的唯一主要死因。随着对COPD相关遗传和分子通路的理解不断深入，越来越需要改进的工具来表征肺功能，以用于将遗传亚型与表型表达结合、监测对新治疗的功能反应或帮助快速开发新型呼吸药物等应用。尽管如此，尽管医学成像中有无数的技术进步，但以适合于人类常规应用的方式获得肺的最基本生理功能的体内区域描绘和量化（气体输送到空气空间以及肺实质和血液的气体摄取）仍然具有挑战性。为了解决这一未满足的需求，该项目利用了我们小组最近开发的一种方法，该方法基于超极化氙-129的磁共振成像（MRI）（hypXe 129），允许同时观察通气的3D分布（气体输送）和气体吸收，以及基于相关通风的区域气体吸收的量化，从适合于呼吸功能受损的受试者的单次短屏气采集。 该项目的第一个目标是在人类受试者中实施并验证该技术的关键改进，包括在图像中分别描绘溶解在红细胞中的hypXe 129的分数和溶解在肺实质/血浆中的hypXe 129的分数的能力。第二个目的是通过测量作为健康受试者中的测量参数和肺充气的函数的信号行为来表征由溶解的hypXe 129信号反映的健康肺中的气体摄取，然后基于信号行为数据导出优化的协议，用于测量气体摄取的相关3D分布。这些优化方案将在轻度和重度COPD受试者中进行验证。第三个也是最后一个目的是在20名健康对照受试者、10名肺量测定正常的吸烟者和30名患有COPD的受试者中进行探索性研究，范围从GOLD 1期到3期，以表征作为疾病严重程度的函数的溶解的hypXe 129和溶解在红细胞和肺实质/血浆中的hypXe 129的分数的标准化气体摄取分布。这些气体摄取结果将与胸部标准计算机断层扫描（CT）和肺功能测试的结果进行比较。成功完成拟议的项目将导致一个改进的，优化版本的方法，同时MR成像的通气和气体摄取，提供标准化的区域气体摄取值，这可以定量比较对象。该技术提供了关于肺的重要功能信息，这是从任何现有的临床成像模式中无法获得的，并且具有提供关于COPD的独特的、生理相关的和临床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.