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Background: A previous study has demonstrated the feasibility of 3D phase-resolved functional lung (PREFUL) MRI in healthy volunteers and patients with chronic pulmonary disease. Before clinical use, the repeatability of the ventilation parameters derived from 3D PREFUL MRI must be determined. Purpose: To evaluate repeatability of 3D PREFUL and to compare with pulmonary functional lung testing (PFT). Study Type: Prospective. Population: Fifty-three healthy subjects and 13 patients with chronic obstructive pulmonary disease (COPD). Field Strength/Sequence: A prototype 3D stack-of-stars spoiled-gradient-echo sequence at 1.5 T. Assessment: Study participants underwent repeated MRI examination (median time interval between scans COPD/healthy subjects [interquartile range]: 7/0 days [6-8/0-0 days]) and one PFT carried out at the time of the baseline MRI. For 3D PREFUL, regional ventilation (RVent) and flow-volume loops were computed and rated by cross-correlation (CC). Also, ventilation time-to-peak (VTTP) was computed. Ventilation defect percentage (VDP) maps were obtained for RVent and CC. Statistical Tests: Repeatability of 3D PREFUL parameters was evaluated using Bland-Altman analysis, coefficient of variation (COV) and intraclass correlation coefficient (ICC). The relation between 3D PREFUL and PFT measures (forced expiratory volume in 1 second (FEV 1 ) and forced vital capacity (FVC) was assessed using the Pearson correlation coefficient (r). Results: In healthy subjects and COPD patients, no significant bias (all P range: 0.09-0.77) and a moderate to good repeatability of RVent, VTTP, and VDP RVent were found (COV range: 0.1%-18.2%, ICC range: 0.51-0.88). For CC and VDP CC moderate repeatability was found (COV range: 0.6%-43.6%, ICC: 0.38-0.60). CC, VDP RVent , and VDP CC showed a good correlation with FEV 1 (all jrj > 0.58, all P < 0.05) and FEV 1 /FVC ratio (all jrj > 0.62, all P < 0.05). Data Conclusion: 3D PREFUL provided a good repeatability of RVent, VTTP, and VDP RVent and moderate repeatability of CC and VDP CC in healthy volunteers and COPD patients, and correlated well with FEV 1 and FEV 1 /FVC. Level of Evidence: 2 Technical Efficacy Stage: 2

Purpose:To reduce acquisition time and improve image quality and robustness of ventilation assessment in a single breath-hold using 1 H-guided reconstruction of fluorinated gas ( 19 F) MRI. Methods: Reconstructions constraining total variation in the image domain, L1 norm in the wavelet domain, and directional total variation between 19 F and 1 H images were compared in order to accelerate 19 F ventilation imaging using retrospectively undersampled data from a healthy volunteer. Using the optimal constrained reconstruction in 8 patients with chronic obstructive pulmonary disease (16-seconds breath-hold), ventilation maps of various acceleration factors (2-fold to 13-fold) were compared with maps of the full data set using the Dice coefficient, difference in volume defect percentage and overlap percentage, as well as hyperpolarized 129 Xe gas MRI. Results: The reconstruction constraining total variation and directional total variation simultaneously performed best in the healthy volunteer (RMS error = 0.07, structural similarity index = 0.77) for a measurement time of 2 seconds. Using the same reconstruction in the patients with chronic obstructive pulmonary disease, the Dice coefficient of defect volumes was 0.86 ± 0.05, the mean difference in volume defect percentage was −1.0 ± 1.7 percentage points, and the overlap percentage was 87% ± 2% for a measurement time of 6 seconds. Between volume defect percentage of 19 F and 129 Xe, a linear correlation (r = 0.75; P = .03) was found, with 19 F volume defect percentage being significantly higher (mean difference = 11%; P = .04). Conclusion: 1 H-guided reconstruction of pulmonary 19 F gas MRI enables reduction of acquisition time while maintaining image quality and robustness of functional parameters.