Purpose or Case Report: MRI is not routinely used in clinical practice for lung imaging because of the low proton density and respiratory motion artifact. However, the ultrashort echo time (UTE) MRI technique can increase the signal in the lung. Image reconstruction techniques, such as iterative motion compensated (iMoCo) reconstruction, have improved respiratory motion management for free-breathing lung MRI scans. With the advantage of no ionizing radiation, MRI can benefit patients with immunodeficiency who often require repeat imaging, patients with heightened radiation sensitivity, and/or pediatric patients. In this abstract, we aim to evaluate the imaging quality of UTE lung MRI in the pediatric population.
Methods & Materials: In this pilot study, we included twelve pediatric patients (age 9.2±4.7 y.o.,6F). Each patient went through a 5-minute free-breathing radial UTE MRI sequence, followed by iMoCo reconstruction. Two types of MR sequences were included: 3D golden angle radial and sequential stack of stars. Six of the patients had CT within one year. Two experienced pediatric radiologists scored the quality of 16 structures in the chest using a Likert scale imaging quality scoring system. The scoring criteria were 1 structure not seen, 2 structure blurred, 3 portion of structure blurred, 4 sharp borders of entire structure, and 5 sharp borders with high subjective SNR.
Results: Statistical analysis shows an inter-class correlation (ICC) of 0.70, 0.73, and 0.72 for MR, CT, and all scores, respectively, suggesting a moderate inter-reader correlation. Cohen’s Kappa is 0.35, 0.35, and 0.37, respectively, suggesting fair inter-reader agreement. While CT has an overall higher score than MRI (p-value≤5e-5), their scores are comparable in the aorta (MR2.5, CT2.4), central lung (MR3.0, CT3.2), and lobar bronchi (MR3.3, CT3.7), with a p-value>0.05. In pulmonary arteries, pleura, peripheral lung, segmental, sub-segmental bronchi, bone, and chest wall soft tissue, CT outperforms MR with p-values≤0.05. We also tested the influence of subgroups. Age under or greater than 12 is not a significant factor for the MRI score, nor is the 3D radial or stack of stars MRI sequence.
Conclusions: While UTE MRI is inferior to CT when resolving smaller structures, it is comparable to its counterpart in some tissues such as the aorta, central lung, and lobar bronchi. UTE lung MRI can be useful for pediatric subjects who need long-term pulmonary monitoring or patients with immunodeficiency, or other patients with increased radiation sensitivity.