Combined Measurement of Pulmonary Inert Gas Washout and Regional Ventilation Heterogeneity by MR of a Single Dose of Hyperpolarized 3He

Washout of inert gases is a measure of pulmonary function well-known in lung physiology. This work presents a method combining inert gas washout and spatially resolved imaging using hyperpolarized He-3, thus providing complementary information on lung function and physiology. The nuclear magnetic resonance signal of intrapulmonary hyperpolarized He-3 is used to track the total amount of gas present within the lungs during multiple-breath washout via tidal breathing. Before the washout phase, 3D ventilation images are acquired using He-3 magnetic resonance imaging from the same dose of inhaled gas. The measured washout signal is corrected for T-1 relaxation and radiofrequency depletion, converting it into a quantity proportional to the apparent amount of gas within the lungs. The use of a pneumotachograph for acquisition of breathing volumes during washout, together with lung volumes derived from the magnetic resonance imaging data, permits assessment of the washout curves against physiological model predictions for healthy lungs. The shape of the resulting washout curves obtained from healthy volunteers matches the predictions, demonstrating the utility of the technique for the quantitative assessment of lung function. The proposed method can be readily integrated with a standard breath-hold He-3 ventilation imaging sequence, thus providing additional information from a single dose of gas. Magn Reson Med 65:1076-1084, 2011. (C) 2010 Wiley-Liss, Inc.