Quantitative assessment of lung ventilation and microstructure in an animal model of idiopathic pulmonary fibrosis using hyperpolarized gas MRI

Rationale and Objectives: The use of hyperpolarized ³He magnetic resonance imaging as a quantitative lung imaging tool has progressed rapidly in the past decade, mostly in the assessment of the airway diseases chronic obstructive pulmonary disease and asthma. This technique has shown potential to assess both structural and functional information in healthy and diseased lungs. In this study, the regional measurements of structure and function were applied to a bleomycin rat model of interstitial lung disease. Materials and Methods: Male Sprague-Dawley rats (weight, 300-350 g) were administered intratracheal bleomycin. After 3 weeks, apparent diffusion coefficient and fractional ventilation were measured by ³He magnetic resonance imaging and pulmonary function testing using a rodent-specific plethysmography chamber. Sensitized and healthy animals were then compared using threshold analysis to assess the potential sensitivity of these techniques to pulmonary abnormalities. Results: No significant changes were observed in total lung volume and compliance between the two groups. Airway resistance elevated and forced expiratory volume significantly declined in the 3-week bleomycin rats, and fractional ventilation was significantly decreased compared to control animals (P < .0004). The apparent diffusion coefficient of ³He showed a smaller change but still a significant decrease in 3-week bleomycin animals (P < .05). Conclusions: Preliminary results suggest that quantitative ³He magnetic resonance imaging can be a sensitive and noninvasive tool to assess changes in an animal interstitial lung disease model. This technique may be useful for longitudinal animal studies and also in the investigation of human interstitial lung diseases.