Robarts Research Institute, Western University, London, Ontario, Canada.
Department of Medical Biophysics, Western University, London, Ontario, Canada.
Respirology. 2022 Feb;27(2):114-133. doi: 10.1111/resp.14197. Epub 2022 Jan 10.
Pulmonary functional MRI (PfMRI) using inhaled hyperpolarized, radiation-free gases (such as He and Xe) provides a way to directly visualize inhaled gas distribution and ventilation defects (or ventilation heterogeneity) in real time with high spatial (mm ) resolution. Both gases enable quantitative measurement of terminal airway morphology, while Xe uniquely enables imaging the transfer of inhaled gas across the alveolar-capillary tissue barrier to the red blood cells. In patients with asthma, PfMRI abnormalities have been shown to reflect airway smooth muscle dysfunction, airway inflammation and remodelling, luminal occlusions and airway pruning. The method is rapid (8-15 s), cost-effective ($300/scan) and very well tolerated in patients, even in those who are very young or very ill, because unlike computed tomography (CT), positron emission tomography and single-photon emission CT, there is no ionizing radiation and the examination takes only a few seconds. However, PfMRI is not without limitations, which include the requirement of complex image analysis, specialized equipment and additional training and quality control. We provide an overview of the three main applications of hyperpolarized noble gas MRI in asthma research including: (1) inhaled gas distribution or ventilation imaging, (2) alveolar microstructure and finally (3) gas transfer into the alveolar-capillary tissue space and from the tissue barrier into red blood cells in the pulmonary microvasculature. We highlight the evidence that supports a deeper understanding of the mechanisms of asthma worsening over time and the pathologies responsible for symptoms and disease control. We conclude with a summary of approaches that have the potential for integration into clinical workflows and that may be used to guide personalized treatment planning.
使用吸入的超极化、无辐射气体（如 3 He 和 129 Xe）的肺部功能磁共振成像（PfMRI）提供了一种实时直接可视化吸入气体分布和通气缺陷（或通气异质性）的方法，具有高空间（mm）分辨率。这两种气体都可以定量测量终末气道形态，而 129 Xe 则可以独特地成像吸入气体穿过肺泡-毛细血管组织屏障转移到红细胞的情况。在哮喘患者中，PfMRI 异常被证明反映了气道平滑肌功能障碍、气道炎症和重塑、管腔阻塞和气道修剪。该方法快速（8-15 秒）、具有成本效益（300 美元/次扫描），并且在患者中耐受性非常好，即使是非常年幼或病重的患者也是如此，因为与计算机断层扫描（CT）、正电子发射断层扫描和单光子发射 CT 不同，它没有电离辐射，检查只需几秒钟。然而，PfMRI 并非没有局限性，包括需要复杂的图像分析、专用设备以及额外的培训和质量控制。我们提供了超极化惰性气体 MRI 在哮喘研究中的三种主要应用的概述，包括：（1）吸入气体分布或通气成像，（2）肺泡微观结构，最后是（3）气体转移到肺泡-毛细血管组织空间以及从组织屏障进入肺部微血管中的红细胞。我们强调了支持更深入了解哮喘随时间恶化的机制以及导致症状和疾病控制的病理学的证据。最后，我们总结了有可能整合到临床工作流程中并可用于指导个体化治疗计划的方法。
