Detection of emphysema in rat lungs by using magnetic resonance measurements of (3)He diffusion

Emphysema is a pulmonary disease characterized by alveolar wall destruction, resulting in enlargement of gas exchange spaces without fibrosis. This condition is a part of chronic obstructive pulmonary disease (COPD), which causes 3.5% of deaths worldwide [Anonymous (1990) World Health Stat. Q. Special, 1–51] and contributes greatly to the global burden of disease [Murray, C. J. & Lopez, A. D. (1996) Science 274, 740–743]. Alveolar regeneration has been shown in animal models and could have potential for clinical treatment of early-stage emphysema. However, current techniques for detection of emphysema are not sensitive at the initial stages. Early-stage human panacinar emphysema is modeled in elastase-treated animals. Here, we provide an in vivo imaging method for differentiating normal and emphysematous rat lungs by measuring the apparent diffusion coefficient (ADC) of hyperpolarized (3)He by using magnetic resonance imaging. These data show that the ADC is significantly larger in elastase-treated rats, indicating alveolar expansion. Whereas these rats were clinically asymptomatic, conventional histology confirmed presence of injury. Our results indicate that measurement of the hyperpolarized (3)He ADC can be a valuable research tool and has potential application in the clinical setting.