Imaging the functional response of the lung to bronchoscopic lung volume reduction

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Summary Advanced emphysema is primarily characterized by chronic inflammation, small airways obstruction, and parenchymal destruction leading to hyperinflation, compromised respiratory mechanics, and progressive functional decline. Medical therapy has proven effective in treating symptoms such as coughing and shortness of breath, and can also help to prevent acute exacerbations, but does little to improve either mortality or restore lost function. While lung volume reduction surgery (LVRS) has demonstrated the ability to improve lung function, quality of life and mortality in certain, rigorously selected patients, it is associated with a significant increase in perioperative and short-term morbidity and remains an underutilized treatment. In 2018, treatment with Zephyr Endobronchial Valves (Zephyr EBV) became the first bronchoscopic lung volume reduction technique to receive FDA approval. Valves are inserted via catheter in order to occlude a target emphysematous lobe, causing partial or complete lobar atelectasis, decreasing residual volume, reducing hyperinflation and improving breathing mechanics and lung function similarly to LVRS with improved morbidity and mortality. Despite numerous studies demonstrating clinically significant average improvements in various functional and anatomical outcome measures, however, there currently remain a significant number of EBV recipients who fail to experience meaningful quality of life benefits as a result. In order to address this discrepancy, the proposed project will use hyperpolarized xenon-129 MRI's unique ability to measure regional lung function, in combination with the assessment of systemic inflammatory biomarkers, to attain a more comprehensive understanding of the mechanisms through which EBV placement perturbs and alters the lung. We hypothesize that this consists primarily of a redistribution of both ventilation and perfusion to the healthier lung as well as a decrease in both local and systemic inflammatory burden—and that sensitively assessing the presence/absence of these changes, as well as their degree, will help to explain the frequent divergence between quantitative and qualitative assessments of EBV treatment efficacy. Using a previously developed multi-breath hyperpolarized 129Xe buildup/washout sequence, combined with a measurement of signal intensity buildup, to produce quantitative maps of minute ventilation and functional residual capacity, we will quantify ventilation redistribution and residual volume at a lobar or segmental level. These maps are compared to registered and segmented CT-derived measurements of airways disease and emphysema. Next, we will employ HP 129Xe dissolved-phase imaging to quantify gas uptake by the red blood cells in the lung—a measurement that relates more closely to blood oxygenation than measurements of perfusion, and investigate the use of dynamic airflow imaging to distinguish clinically important cases of collateral ventilation and leakage around the valve. Finally, we will evaluate a number of systemic inflammatory biomarkers, as well as inflammatory cells such as activated macrophages and CD8+ T cells, whose presence we will attempt to correlate with subjectively quality of life assessments post-treatment.