Feasibility of oxygen-enhanced MRI at 7T for assessing lung functional alterations in rats

Oxygen-enhanced (OE) magnetic resonance imaging (MRI) provides a non-invasive approach for assessing lung function. Its application in preclinical models is challenging due to rapid respiratory motion, the intrinsically short T₂* of lung tissue and susceptibility to magnetic field inhomogeneity. These limitations can be largely overcome using standard radial pulse sequences with ultra-short echo, combined with robust T₁-mapping techniques that include B₁⁺-field correction to ensure accurate quantification of regional oxygenation. In this study, we applied the Double Angle Method (DAM) to correct B₁⁺-field inhomogeneity for variable flip angle (VFA) T₁-mapping. Lung images were acquired using a 3D ultrashort echo time (UTE) sequence, enabling assessment of regional T₁ values during ambient air and 95% O₂ inhalation. Both healthy control rats and animals with acute lung inflammation induced by intratracheal lipopolysaccharide (LPS) were studied. Baseline T₁ values in the lung parenchyma were higher in LPS-treated animals compared to controls, with visually identified inflamed regions showing the greatest elevation. Upon inhalation of 95% O₂, T₁ decreased in all groups, but the relative reduction was smaller in LPS-treated lungs than in controls and minimal in inflamed regions, indicating impaired regional oxygen responsiveness. These results demonstrate the feasibility of OE MRI for detecting localized functional impairments in the lungs caused by inflammation.