A Hybrid Multibreath Wash-in Wash-out Lung Function Quantification Scheme in Human Subjects Using Hyperpolarized 3He MRI for Simultaneous Assessment of Specific Ventilation, Alveolar Oxygen Tension, Oxygen Uptake, and Air Trapping
To present a method for simultaneous acquisition of alveolar oxygen tension (PAO2), specific ventilation (SV), and apparent diffusion coefficient (ADC) of hyperpolarized (HP) gas in the human lung, allowing reinterpretation of the PAO2 and SV maps to produce a map of oxygen uptake (R).Method:
An imaging scheme was designed with a series of identical normoxic HP gas wash-in breaths to measure ADC, SV, PAO2, and R in less than 2 min. Signal dynamics were fit to an iterative recursive model that regionally solved for these parameters. This measurement was successfully performed in 12 subjects classified in three healthy, smoker, and chronic obstructive pulmonary disease (COPD) cohorts.Results:
The overall whole lung ADC, SV, PAO2, and R in healthy, smoker, and COPD subjects was 0.20 ± 0.03 cm2/s, 0.39 ± 0.06,113 ± 2 Torr, and 1.55 ± 0.35 Torr/s, respectively, in healthy subjects; 0.21 ± 0.03 cm2/s, 0.33 ± 0.06, 115.9 ± 4 Torr, and 0.97 ± 0.2 Torr/s, respectively, in smokers; and 0.25 ± 0.06 cm2/s, 0.23 ± 0.08, 114.8 ± 6.0Torr, and 0.94 ± 0.12 Torr/s, respectively, in subjects with COPD. Hetrogeneity of SV, PAO2, and R were indicators of both smoking-related changes and disease, and the severity of the disease correlated with the degree of this heterogeneity. Subjects with symptoms showed reduced oxygen uptake and specific ventilation.Conclusion:
High-resolution, nearly coregistered and quantitative measures of lung function and structure were obtained with less than 1 L of HP gas. This hybrid multibreath technique produced measures of lung function that revealed clear differences among the cohorts and subjects and were confirmed by correlations with global lung measurements.