Three-dimensional quantitative MRI of aerosolized gadolinium-based nanoparticles and contrast agents in isolated...

The objective of this study is to evaluate the suitability and performance of ultra-short echo time (UTE) sequences for imaging and quantifying the deposition of nebulized MRI contrast agents in human-sized lungs.

Nebulization of clinically used contrast agent or gadolinium-based nanoparticles were performed using a commercial jet nebulizer in isolated and ventilated porcine lungs connected to a 3D-printed human upper airways replica. MR images of isolated lungs were acquired on a 3T clinical MR scanner using 3D UTE sequences at different flip angles.

3D acquisitions with isotropic millimetric resolution were obtained in less than 4 min. Images exhibit homogeneous and large MR signal enhancement (above 200%) following nebulization of both types of aerosols. Deposition of aerosol down to the level of the bronchi of secondary lobules was visualized. T₁ values and the concentration of nanoparticles obtained by MRI were found to correlate with the amount of nebulized gadolinium³⁺ ions.

The distribution of aerosolized gadolinium-based contrast agent or nanoparticles can be visualized and quantified using UTE MRI in large animal ventilated lung model on a clinical MRI scanner. This protocol can be used for assessing and quantifying aerosol regional deposition with high spatial resolution (1 mm 3D isotropic) without ionizing radiation and could be applied in the future for diagnostic or therapeutic applications in patients.