Longitudinal and noninvasive assessment of emphysema evolution in a murine model using proton MRI.

Ultrashort echo time (550 μs) MR imaging was implemented to track the emphysema development in mice lung challenged with elastase. Two parameters, namely, signal intensity and T 2, were used to monitor the disease evolution. Nine mice were imaged before and at 24 h as well as at 3 and 8 weeks after elastase instillation. Five mice instilled with saline served as controls. At week 8, the mean normalized signal intensity ± SD was 0.89 ± 0.20 for healthy controls and 0.64 ± 0.10 for animals with emphysema. Similarly, a reduced value of T 2 (1.27 ± 0.35 ms vs 0.96 ± 0.18 ms) was found in the emphysema group. The mean signal intensity drop and the reduction of T 2 were prominent at 3 weeks following elastase instillation and stabilized between 3 and 8 weeks. The results indicated an excellent agreement between MR findings and histological morphometry (signal intensity, r = -0.78, P = 0.004; T 2, r = -0.78, P = 0.001). This result shows that proton MRI allows structural changes at alveolar level to be monitored longitudinally. This technique, applied routinely in preclinical trials will represent a valuable tool for assessment of drug therapy efficacy.