Niedbalski Peter J, Bier Elianna A, Wang Ziyi, Willmering Matthew M, Driehuys Bastiaan, Cleveland Zackary I
Center for Pulmonary Imaging Research, Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.
Departement of Biomedical Engineering, Duke University, Durham, North Carolina.
J Appl Physiol (1985). 2020 Aug 1;129(2):218-229. doi: 10.1152/japplphysiol.00186.2020. Epub 2020 Jun 18.
Magnetic resonance (MR) imaging and spectroscopy using dissolved hyperpolarized (HP) Xe have expanded the ability to probe lung function regionally and noninvasively. In particular, HP Xe imaging has been used to quantify impaired gas uptake by the pulmonary tissues. Whole-lung spectroscopy has also been used to assess global cardiogenic oscillations in the MR signal intensity originating from Xe dissolved in the red blood cells of pulmonary capillaries. Herein, we show that the magnitude of these cardiogenic dynamics can be mapped three dimensionally using radial MRI, because dissolved Xe dynamics are encoded directly in the raw imaging data. Specifically, 1-point Dixon imaging is combined with postacquisition keyhole image reconstruction to assess regional blood volume fluctuations within the pulmonary microvasculature throughout the cardiac cycle. This "oscillation mapping" was applied in healthy subjects (mean amplitude 9% of total RBC signal) and patients with pulmonary arterial hypertension (PAH; mean 4%) and idiopathic pulmonary fibrosis (IPF; mean 14%). Whole-lung mean values from these oscillation maps correlated strongly with spectroscopy and clinical pulmonary function testing, but exhibited significant regional heterogeneity, including gravitationally dependent gradients in healthy subjects. Moreover, regional oscillations were found to be sensitive to disease state. Greater percentages of the lungs exhibit low-amplitude oscillations in PAH patients, and longitudinal imaging shows high-amplitude oscillations increase significantly over time (4-14 mo, = 0.02) in IPF patients. This technique enables regional dynamics within the pulmonary capillary bed to be measured, and in doing so, provides insight into the origin and progression of pathophysiology within the lung microvasculature. Spatially heterogeneous abnormalities within the lung microvasculature contribute to pathology in various cardiopulmonary diseases but are difficult to assess noninvasively. Hyperpolarized Xe MRI is a noninvasive method to probe lung function, including regional gas exchange between pulmonary air spaces and capillaries. We show that cardiogenic oscillations in the raw dissolved Xe MRI signal from pulmonary capillary red blood cells can be imaged using a postacquisition reconstruction technique, providing a new means of assessing regional lung microvasculature function and disease state.
利用溶解的超极化（HP）氙进行磁共振（MR）成像和波谱分析，已扩展了区域和非侵入性探测肺功能的能力。特别是，HP氙成像已被用于量化肺组织气体摄取受损情况。全肺波谱分析也已被用于评估源自溶解在肺毛细血管红细胞中的氙的MR信号强度的整体心源性振荡。在此，我们表明，这些心源性动力学的幅度可以使用径向MRI进行三维映射，因为溶解的氙动力学直接编码在原始成像数据中。具体而言，将1点狄克逊成像与采集后锁孔图像重建相结合，以评估整个心动周期内肺微血管内的区域血容量波动。这种“振荡映射”应用于健康受试者（平均幅度为总红细胞信号的9%）以及肺动脉高压（PAH；平均4%）和特发性肺纤维化（IPF；平均14%）患者。这些振荡图的全肺平均值与波谱分析和临床肺功能测试密切相关，但表现出显著的区域异质性，包括健康受试者中与重力相关的梯度。此外，发现区域振荡对疾病状态敏感。PAH患者肺部更大比例表现为低幅度振荡，纵向成像显示IPF患者高幅度振荡随时间显著增加（4 - 14个月，P = 0.02）。该技术能够测量肺毛细血管床内的区域动力学，从而深入了解肺微血管病理生理学的起源和进展。肺微血管内的空间异质性异常导致各种心肺疾病的病理变化，但难以进行非侵入性评估。超极化氙MRI是一种探测肺功能的非侵入性方法，包括肺气腔与毛细血管之间的区域气体交换。我们表明，使用采集后重建技术可以对来自肺毛细血管红细胞的原始溶解氙MRI信号中的心源性振荡进行成像，为评估区域肺微血管功能和疾病状态提供了一种新方法。
