Comparison of Signal‐ and Volume‐Based Ventilation‐Weighted Assessment Using 3D FLORET UTE MRI in Patients With Various Pulmonary Disease

ABSTRACT Purpose 3D free‐breathing, proton, contrast‐agent‐free MR methods are increasingly used for pulmonary ventilation‐weighted measurements. The methods are split between: (1) signal‐based, which rely on lung parenchyma signal changes during respiration, and (2) volume‐based that utilize the Jacobian determinant of deformation fields from the image registration. This study compares both proton methods using respiratory‐resolved images acquired using fermat‐looped orthogonally encoded trajectories (FLORET) acquisition. Methods Free‐breathing FLORET data were acquired from participants with various pulmonary conditions ( N = 29) and healthy controls ( N = 7), and reconstructed into respiratory phase‐resolved images. Signal‐based regional ventilation (RVent) was quantified using the 3D phase‐resolved functional lung algorithm, and volume‐based Jacobian ventilation (JVent) was derived as the Jacobian of the deformation field from the direct image registration of the end‐expiratory image to the end‐inspiratory image. Differences between the means, coefficients of variation (CoVs), and their ventilation defect percent (VDP) were quantified by Bland–Altman plots. The spatial overlap of the defect maps was determined by multi‐class Sørensen–Dice coefficient, and Spearman correlations to 129 Xe MRI were assessed. Results In all study participants, statistically significant differences were found between means/CoVs of RVent and JVent parameters (both p < 0.0001), but not VDP ( p = 0.38). The median spatial overlap of the defect maps was 86%. VDP RVent showed stronger correlation ( ρ = 0.78, Meng Z = 4.36, p < 0.0001) to VDP 129Xe than JVent ( ρ = 0.34). Conclusion Although both proton lung MRI methods successfully identified ventilation defects, the stronger correlation between signal‐based and 129 Xe MRI indicates that RVent may provide a more reliable assessment of lung ventilation in clinical applications in comparison to volume‐based parameters.