Quantitative and Regional Analysis of Lung Function Assessed by Hyperpolarized Xe-129 MRI

Lungs handle human gas exchange with atmosphere through respiration. Nowadays, more and more people suffer from respiratory disorders. However, the lack of regional or functional information of conventional techniques in assessing lung function limits their application. Quantitative techniques with the ability to provide regional information of lung structure and function are valuable in lung disease diagnosis and treatment. Hyperpolarized gas (HPG) MRI, as it provides the image of lung structure and function with high spatial and temporal resolution, gives an opportunity to quantitatively and regionally assess lung function. Hyperpolarized Xenon-129 ventilation MRI has the ability to detect ventilation defects where are absent or have relatively low signal intensity within the lung. Dissolved-phase MRI can measure gas uptake by lung parenchyma and blood flow. Progress in deep learning makes it possible to quantify ventilation defect percentage and gas uptake ratios among different lung lobes, providing valuable information for regional analysis of these measurements. However, current HPG imaging lacks standardization, making it difficult to interpret study results among different subjects and institutions. In this study, we investigated the ventilation defect percentage (VDP) of 50 healthy subjects diversified race, gender, age, BMI and smoking history. Our findings would serve as a reference for the VDP in health subjects. For dissolved-phase MRI, we found the lung volume during MRI scan influences the resulting gas uptake ratios. We investigated a total of 17 subjects including 11 healthy subjects and 5 COPD patients who underwent dissolved-phase MRI in three different lung inflation levels. We got strong inverse correlations between lung inflation level and gas uptake measurements obtained by hyperpolarized Xe-129 MRI. Regional distribution of gas uptake and the influence of different inflation levels on each lobe were further investigated. These results would benefit the standardization and popularity of hyperpolarized Xe-129 MRI in the application of assessing lung function.