Reproducibility of non-contrast enhanced multi breath-hold ultrashort echo time functional lung MRI

Purpose: To evaluate the intraindividual reproducibility of functional lung imaging using non-contrast enhanced multi breath-hold 3D-UTE MRI.Methods: Ten healthy volunteers underwent non-contrast enhanced 3D-UTE MRI at three time points for same -day and different-day measurements employing a stack-of-spirals trajectory at 3 T. At each time point, inspi-ratory and expiratory breathing states were acquired for tidal and deep breathing, each within a single breath -hold. For functional image analysis, fractional ventilation (FV) was calculated pixelwise after image registration from the MR signal change. To decouple FV from breathing depth, the individual lung volume was used for volume adjustment (rFV). Reproducibility evaluation was performed in eight lung segments. Statistical analyses included two way mixed intraclass correlation (ICC), sign-test, Friedman-test and modified Bland-Altman analyses.Results: FV from tidal breathing showed an ICC of 0.81, a bias of 1.3% and an interval of confidence (CI) ranging from-67.1 to 69.6%. FV from deep breathing was higher reproducible with an ICC of 0.92 (bias,-0.2%; CI,-34.2 to 33.7%). Following volume adjustment, reproducibility of rFV for tidal breathing improved (ICC, 0,86; bias, 2.0%; CI,-34.3 to 38.3%), whereas it did not bear significant benefits for deep breathing (ICC, 0.89; bias, 2.8%; CI,-24.9 to 30.5%). Reproducibility was independent from the examination day. Conclusion: Non-contrast-enhanced multi breath-hold 3D-UTE MRI allows for highly reproducible ventilation imaging.