Purpose To test the feasibility of 3D phase‐resolved functional lung (PREFUL) MRI in healthy volunteers and patients with chronic pulmonary disease, to compare 3D to 2D PREFUL, and to investigate the required temporal resolution to obtain stable 3D PREFUL measurement. Methods Sixteen participants underwent MRI using 2D and 3D PREFUL. Retrospectively, the spatial resolution of 3D PREFUL (4 × 4 × 4 mm3) was decreased to match the spatial resolution of 2D PREFUL (4 × 4 × 15 mm3), abbreviated as 3Dlowres. In addition to regional ventilation (RVent), flow‐volume loops were computed and rated by a cross‐correlation (CC). Ventilation defect percentage (VDP) maps were obtained. RVent, CC, VDPRVent, and VDPCC were compared for systematic differences between 2D, 3Dlowres, and 3D PREFUL. Dividing the 3D PREFUL data into 4‐ (≈ 20 phases), 8‐ (≈ 40 phases), and 12‐min (≈ 60 phases) acquisition pieces, the ventilation parameter maps, including the heterogeneity of ventilation time to peak, were tested regarding the required temporal resolution. Results RVent, CC, VDPRVent, and VDPCC presented significant correlations between 2D and 3D PREFUL (r = 0.64‐0.94). CC and VDPCC of 2D and 3Dlowres PREFUL were significantly different (P < .0113). Comparing 3Dlowres and 3D PREFUL, all parameters were found to be statistically different (P < .0045). Conclusion 3D PREFUL MRI depicts the whole lung volume and breathing cycle with superior image resolution and with likely more precision compared to 2D PREFUL. Furthermore, 3D PREFUL is more sensitive to detect regions of hypoventilation and ventilation heterogeneity compared to 3Dlowres PREFUL, which is important for early detection and improved monitoring of patients with chronic lung disease.

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 The purpose of this study is to evaluate the influence of different field strengths on perfusion and ventilation parameters, SNR and CNR derived by PREFUL MRI using predefined sequence parameters. Methods Data sets of free breathing 2d FLASH lung MRI were acquired from 15 healthy subjects at 1.5T and 3T (Magnetom Avanto and Skyra, Siemens Healthcare, Erlangen, Germany) with a maximum period of 3 days in between. The processed functional parameters regional ventilation (RVent), perfusion (Q), quantified perfusion (QQuant), perfusion defect percentage (QDP), ventilation defect percentage (VDP) and ventilation-perfusion match (VQM) were compared for systematic differences. Signal- and contrast-to-noise ratio (SNR and CNR) of both acquisitions were analyzed. Results RVent, Q, VDP, SNR and CNR presented no significant differences between 1.5T and 3T. QQuant (1.5T vs. 3T, P = 0.04), and QDP (1.5T vs. 3T, P≤0.01) decreased significantly at 3T. Consequently, VQM increased significantly (1.5T vs. 3T, P≤0.01). Skewness and kurtosis of the Q-values increased significantly at 3T (P≤0.01). The mean Sørensen-Dice coefficients between both series were 0.91 for QDP and 0.94 for VDP. The Bland-Altman analysis of both series showed mean differences of 4.29% for QDP, 1.23% for VDP and -5.15% for VQM. Using the above-mentioned parameters for three-day repeatability at two different scanners and field strengths, the retrospective power calculation showed, that a sample size of 15 can detect differences of 3.7% for QDP, of 2.9% for VDP and differences of 2.6% for VQM. Conclusion Significant differences in QDP may be related to field inhomogeneities, which is expressed by increasing skewness and kurtosis at 3T. QQuant reveals only poor reproducibility between 1.5T and 3T. RVent, Q, VDP, SNR and CNR were not altered significantly at the used sequence parameters. Healthy participants with minimal defects present high spatial agreement of QDP and VDP.