Evaluating Stack-of-Stars and FLORET 3D Ultrashort Echo Time MRI to Assess Structural Pathology in Cystic Fibrosis...

Free-breathing structural lung MRI using 3D Ultrashort Echo Time (UTE) techniques has advanced substantially; however, image quality and diagnostic performance can vary depending on the acquisition strategy. Stack-of-Stars (SoS) is a commonly available UTE method, whereas FLORET (Fermat Looped, Orthogonally Encoded Trajectories) enables more efficient and isotropic k-space sampling. Thus, the purpose of this study was to compare the image quality and diagnostic performance of SoS and FLORET 3D UTE MRI in detecting structural lung abnormalities in individuals with cystic fibrosis (CF).

Six individuals with CF (24.6 ± 7.3 years) underwent free-breathing lung MRI using multi-echo SoS for bronchiectasis T₂* mapping. An additional 25 individuals with CF (15.6 ± 4.9 years) underwent lung MRI using SoS and FLORET UTE sequences for structural evaluation. Image quality was assessed using Likert scores, signal ratio (Sr), and contrast ratio (Cr). Brody scores for five CF-related abnormalities were compared to CT acquired within 3 years. Wilcoxon tests, Pearson correlations, and kappa statistics were used for analysis.

FLORET demonstrated significantly higher Sr (216 ± 60 vs 153 ± 76) and Cr (15.1 ± 5.2 vs 6.8 ± 9.6) than SoS (P < .001). Qualitative image scores were superior for FLORET across all domains. FLORET Brody scores correlated strongly with CT (R² = 0.95, κ = 0.94), while SoS showed weaker agreement (R² = 0.40, κ = 0.44). Inter-reader agreement was also higher with FLORET (R² = 0.70, κ = 0.82).

FLORET 3D UTE MRI provides superior image quality, improved diagnostic agreement, and stronger correlation with CT compared to SoS, supporting its use as a radiation-free alternative for structural assessment in CF lung disease.