Dynamic ventilation 3He MRI for the quantification of disease in the rat lung

Pulmonary diseases are known to be largely inhomogeneous. To evaluate such inhomogeneities, we are testing an image-based method to measure gas flow in the lung regionally. Dynamic, spin-density-weighted hyperpolarized (3)He MR images performed during slow inhalation of this gas were analyzed to quantify regional inflation rate. This parameter was measured in regions of interest (ROIs) that were defined by a rectangular grid that covered the entire rat lung and grew dynamically with it during its inflation. We used regional inflation rate to quantify elastase-induced emphysema and to differentiate healthy (n = 8) from elastase-treated (n = 9) rat lungs as well as healthy from elastase-treated areas of one rat unilaterally treated with elastase in the left lung. Emphysema was also assessed by gold standard morphological and well-established hyperpolarized (3)He MRI diffusion measurements. Mean values of regional inflation rates were significantly different for healthy and elastase-treated animals and correlated well with the apparent diffusion coefficient of (3)He and morphological measurements. The image-based biomarker inflation rate may be useful for the assessment of regional lung ventilation.