Purpose: To investigate the in vivo T1 -enhancement of the lung parenchyma in free-breathing healthy mice following intratracheal administration of Gd-DOTA-based nanoparticles, to assess the enhancement kinetics of the instilled contrast medium and to identify its elimination pathways.
Methods: Ultrashort Echo Time (276 μs) proton MRI of the lung was performed (N = 14) at 4.7 T after the intratracheal instillation of 50 μL of seven different concentrations of contrast agent solution (from 2 to 100 mM of Gd(3+) ). The signal enhancement (SE) in lungs, blood, liver, kidneys, and bladder was assessed (N = 3) for a 50 mM concentration solution at different time points.
Results: The largest SE in lungs (266 ± 14%) was observed for a 50 mM solution of Gd(3+) . In lungs, the SE was observed to decay exponentially with a time constant of 149 ± 51 min. The passage of the nanoparticles from lung tissue to blood and kidneys, and ultimately to the bladder, was observed. No significant hepatic enhancement was measured.
Conclusion: This study demonstrates the feasibility of large SEs of lung tissue using intratracheally administrated solutions of Gd-based contrast agents. In future applications, the SE in lungs could be used to image the biodistribution of coadministrated drug aerosols or to selectively enhance lung diseased tissues.
Keywords: UTE; contrast agent; gadolinium; lung proton MRI; nanoparticles.
Copyright © 2012 Wiley Periodicals, Inc.