Purpose
To initiate the archive of relaxation‐weighted images that may help discriminate between pulmonary pathologies relevant to acute respiratory distress syndrome. MRI has the ability to distinguish pathologies by providing a variety of different contrast mechanisms. Lungs have historically been difficult to image with MRI but image quality is sufficient to begin cataloging the appearance of pathologies in T1‐ and T2‐weighted images. This study documents T1 and the use of T1 contrast with four experimental rat lung pathologies.
Methods
Inversion‐recovery and spoiled steady state images were made at 1.89 T to measure T1 and document contrast in rats with atelectasis, lipopolysaccharide‐induced inflammation, ventilator‐induced lung injury (VILI), and injury from saline lavage. Higher‐resolution Ernst‐angle images were made to see patterns of lung infiltrations.
Results
T1‐weighted images showed minimal contrast between pathologies, similar to T1‐weighted images of other soft tissues. Images taken shortly after magnetization inversion and displayed with inverted contrast highlight lung pathologies. Ernst‐angle images distinguish the effects of T1 relaxation and spin density and display distinctive patterns. T1 for pathologies were: atelectasis, 1.25 ± 0.046 s; inflammation from instillation of lipopolysaccharide, 1.24 ± 0.015 s; VILI, 1.55 ± 0.064 s (p = 0.0022 vs. normal lung); and injury from saline lavage, 1.90±0.080 s (p = 0.0022 vs. normal lung; p = 0.0079 vs. VILI). T1 of normal lung and erector spinae muscle were 1.25 ± 0.028 s and 1.02 ± 0.027 s, respectively (p = 0.0022).
Conclusions
Traditional T1‐weighting is subtle. However, images made with inverted magnetization and inverted contrast highlight the pathologies and Ernst‐angle images aid in distinguishing pathologies.