Mapping Alveolar Oxygen Partial Pressure in COPD Using Hyperpolarized Helium-3: The Multi-Ethnic Study of Atherosclerosis (MESA) COPD Study

Chronic obstructive pulmonary disease (COPD) and emphysema are characterized by functional and structural damage which increases the spaces for gaseous diffusion and impairs oxygen exchange. Here we explore the potential for hyperpolarized (HP) (3)He MRI to characterize lung structure and function in a large-scale population-based study. Participants (n = 54) from the Multi-Ethnic Study of Atherosclerosis (MESA) COPD Study, a nested case-control study of COPD among participants with 10+ packyears underwent HP (3)He MRI measuring p(A)O(2), apparent diffusion coefficient (ADC), and ventilation. HP MRI measures were compared to full-lung CT and pulmonary function testing. High ADC values (>0.4 cm(2)/s) correlated with emphysema and heterogeneity in p(A)O(2) measurements. Strong correlations were found between the heterogeneity of global p(A)O(2) as summarized by its standard deviation (SD) (p < 0.0002) and non-physiologic p(A)O(2) values (p < 0.0001) with percent emphysema on CT. A regional study revealed a strong association between p(A)O(2) SD and visual emphysema severity (p < 0.003) and an association with the paraseptal emphysema subtype (p < 0.04) after adjustment for demographics and smoking status. HP noble gas p(A)O(2) heterogeneity and the fraction of non-physiological p(A)O(2) results increase in mild to moderate COPD. Measurements of p(A)O(2) are sensitive to regional emphysematous damage detected by CT and may be used to probe pulmonary emphysema subtypes. HP noble gas lung MRI provides non-invasive information about COPD severity and lung function without ionizing radiation.