This study shows the feasibility of phase-resolved functional lung imaging to gain quantitative information regarding regional lung perfusion and ventilation without the need for ultrafast imaging, which will be advantageous for future clinical translation. Magn Reson Med 79:2306-2314, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

BackgroundPerfusion‐weighted (Qw) noncontrast‐enhanced proton lung MRI is a promising technique for assessment of pulmonary perfusion, but still requires validation.PurposeTo improve perfusion‐weighted phase‐resolved functional lung (PREFUL)‐MRI, to validate PREFUL with perfusion single photon emission computed tomography (SPECT) as a gold standard, and to compare PREFUL with dynamic contrast‐enhanced (DCE)‐MRI as a reference.Study TypeRetrospective.PopulationTwenty patients with chronic obstructive pulmonary disease (COPD), 14 patients with cystic fibrosis (CF), and 21 patients with chronic thromboembolic pulmonary hypertension (CTEPH) were included.Field Strength/SequenceFor PREFUL‐MRI, a spoiled gradient echo sequence and for DCE‐MRI a 3D time‐resolved angiography with stochastic trajectories sequence were used at 1.5T.AssessmentPREFUL‐MRI coronal slices were acquired in free‐breathing. DCE‐MRI was performed in breath‐hold with injection of 0.03 mmol/kg bodyweight of gadoteric acid at a rate of 4 cc/s. Perfusion SPECT images were obtained for six CTEPH patients. Images were coregistered. An algorithm to define the appropriate PREFUL perfusion phase was developed using perfusion SPECT data. Perfusion defect percentages (QDP) and Qw‐values were calculated for all methods. For PREFUL quantitative perfusion values (PREFULQ) and for DCE pulmonary blood flow (PBF) was calculated.Statistical TestsObtained parameters were assessed using Pearson correlation and Bland–Altman analysis.ResultsQw‐SPECT correlated with Qw‐DCE (r = 0.50, P < 0.01) and Qw‐PREFUL (r = 0.47, P < 0.01). Spatial overlap of QDP maps showed an agreement ≥67.7% comparing SPECT and DCE, ≥64.1% for SPECT and PREFUL, and ≥60.2% comparing DCE and PREFUL. Significant correlations of Qw‐PREFUL and Qw‐DCE were found (COPD: r = 0.79, P < 0.01; CF: r = 0.77, P < 0.01; CTEPH: r = 0.73, P < 0.01). PREFULQ/PBF correlations were similar/lower (CF, CTEPH: P > 0.12; COPD: P < 0.01) compared to Qw‐PREFUL/DCE correlations. PREFULQ‐values were higher/similar compared to PBF‐values (COPD, CF: P < 0.01; CTEPH: P = 0.026).Data ConclusionThe automated PREFUL algorithm may allow for noncontrast‐enhanced pulmonary perfusion assessment in COPD, CF, and CTEPH patients comparable to DCE‐MRI.Level of Evidence 3Technical Efficacy Stage 2J. Magn. Reson. Imaging 2020;52:103–114.

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 Free‐breathing phase‐resolved functional lung (PREFUL)‐MRI may be useful for treatment monitoring in chronic obstructive pulmonary disease (COPD) patients with dyspnea. PREFUL test–retest reliability is essential for clinical application. Purpose To measure the repeatability of PREFUL‐MRI ventilation (V) and perfusion (Q) parameters. Study Type Retrospective and prospective. Population A total of 28 COPD patients and 57 healthy subjects. Field Strength/Sequence 1.5T MRI/2D spoiled gradient echo imaging. Assessment V and Q lung parameter maps based on three coronal slices were obtained at baseline and after 14 days (COPD patients) or after a short pause outside the scanner (healthy subjects). Regional ventilation (RVent) and imaging flow volume loops by cross‐correlation (ccVent) were quantified. Q was normalized to the signal of the main pulmonary artery (QN) and quantified (QQuant). Pulmonary pulse wave transit time (pPTT), voxel‐by‐voxel (regional), and whole lung (global) ventilation defect percentage based on RVent (VDPRVent) and ccVent (VDPccVent), perfusion defect percentage (QDP), and ventilation/perfusion match based on RVent (VQMRVent) and ccVent (VQMccVent) were calculated. Statistical Tests Regional V and Q were analyzed globally for each subject. Each parameter's median of scans 1 and 2 were assessed by Wilcoxon sign rank test. A parameter's repeatability was analyzed by Bland–Altman analyses, coefficients of variation, intraclass correlation coefficients (ICC), and power calculations. The regional voxel repeatability was examined by calculating the Sørensen–Dice coefficient. Results There was no bias and no significant differences between the first and second MRI for any parameters (P > 0.05). Coefficient of variation ranged from 2.26% (ccVent) to 19.31% (QDP), ICC from 0.93 (QDP) to 0.60 (pPTT), the smallest detectable difference was 0.002 ccVent. Regional comparison showed the highest overlap (84%) in VDPRVent in healthy voxels and the lowest (53%) in VDPccVent defect voxels. Data Conclusion V and Q PREFUL‐MRI parameters were repeatable over two scan sessions in both healthy controls and COPD patients. Level of Evidence 2 Technical Efficacy Stage 2