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This study aimed to examine the alterations in magnetic resonance imaging (MRI) characteristics of bioabsorbable magnesium (Mg) screws over time in a single center study in humans.

Phase‐resolved functional lung (PREFUL) MRI is a proton‐based, contrast agent‐free technique derived from the Fourier decomposition approach to measure regional ventilation and perfusion dynamics during free‐breathing. Besides the necessity of extensive PREFUL postprocessing, the utilized MRI sequence must fulfill specific requirements. This study investigates the impact of sequence selection on PREFUL‐MRI–derived functional parameters by comparing the standard spoiled gradient echo (SPGRE) sequence with a lung‐optimized balanced steady‐state free precession (bSSFP) sequence, thereby facilitating PREFULs clinical application in pulmonary disease assessment. This study comprised a prospective dataset of healthy volunteers and a retrospective dataset of patients with suspected chronic thromboembolic pulmonary hypertension. Both cohorts underwent PREFUL‐MRI with both sequences to assess the correspondence of PREFUL ventilation and perfusion parameters (A). Additionally, healthy subjects were scanned a second time to evaluate repeatability (B), whereas patients received dynamic contrast‐enhanced (DCE)‐MRI, considered the perfusion gold standard for comparison with PREFUL‐MRI (C). Signal‐to‐noise ratio (SNR), calculated from the unprocessed images, was compared alongside median differences of PREFUL‐MRI–derived parameters using a paired Wilcoxon signed rank test. Further evaluations included calculation of the Pearson correlation, intraclass‐correlation coefficient for repeatability assessment, and spatial overlap (SO) for regional comparison of PREFUL‐MRI and DCE‐MRI. bSSFP showed a clear SNR advantage over SPGRE (median: 23 vs. 9, p < 0.001). (A) Despite significant differences, parameter values were strongly correlated (r ≥ 0.75). After thresholding, binary maps showed high healthy overlap across both cohorts (SOHealthy > 86%) and high defect overlap in the patient cohort (SODefect ≥ 48%). (B) bSSFP demonstrated slightly higher repeatability across most parameters. (C) Both sequences demonstrated comparable correspondence to DCE‐MRI, with SPGRE excelling in absolute quantification and bSSFP in spatial agreement. Although bSSFP showed superior SNR results, both sequences displayed spatial defect concordance and highly correlated PREFUL parameters with deviations regarding repeatability and alignment with DCE‐MRI. [ABSTRACT FROM AUTHOR]

Background: Phase-resolved functional lung (PREFUL) magnetic resonance imaging (MRI) pulmonary pulse wave transit time (pPTT) is a contrast agent free, vascular imaging biomarker, but has not been validated in chronic obstructive pulmonary disease (COPD).Purpose: To validate PREFUL with echocardiographic pPTT as a reference standard and to compare arterial/venous pPTT mapping with spirometry and clinical parameters.Study Type: Prospective.Population: Twenty-one patients (62% female) with COPD and 44 healthy participants (50% female).Field Strength/sequence: 1.5 T; 2D-spoiled gradient-echo sequence.Assessment: Three coronal PREFUL MRI slices, echocardiography, and spirometry including forced expiratory volume in 1 second (FEV1, liter) and predicted defined as FEV1 in% divided by the population average FEV1%, were performed. Pulmonary pulse transit time from the main artery to the microvasculature (PREFUL pPTT), to the right upper lobe vein (PREFUL pPTTav , echo pPTTav ), from microvasculature to right upper lobe vein (PREFULvein ) and the ratio of PREFUL pPTT to PREFUL pPTTvein were calculated. Body mass index (BMI), Global Initiative for COPD (GOLD) stage 1-4, disease duration, and cigarette packs smoked per day multiplied by the smoked years (pack years) were computed.Statistical Tests: Shapiro-Wilk-test, paired-two-sided-t-tests, Bland-Altman-analysis, coefficient of variation, Pearson ρ were applied, pPTT data were compared between 21 subjects from the 44 healthy subjects who were age- and sex-matched to the COPD cohort, P < 0.05 was considered statistically significant.Results: PREFUL pPTTav significantly correlated with echo pPTTav (ρ = 0.95) with 1.85 msec bias, 95% limits of agreement: 55.94 msec, -52.23 msec in all participants (P = 0.59). In the healthy participants, PREFUL and echo pPTTav significantly correlated with age (ρ = 0.81, ρ = 0.78), FEV1 (ρ = -0.47, ρ = -0.34) and BMI (ρ = 0.56, ρ = 0.51). In COPD patients, PREFUL pPTT significantly correlated with FEV1 predicted (ρ = -0.59), GOLD (ρ = 0.53), disease duration (ρ = 0.54), and pack years (ρ = 0.49).Data Conclusion: Arteriovenous PTT measured by PREFUL MRI corresponds precisely to echocardiography and appears to be feasible even in severe COPD.Evidence Level: 1 TECHNICAL EFFICACY: Stage 2. [ABSTRACT FROM AUTHOR]

Background: Regional flow volume loop ventilation‐weighted noncontrast‐enhanced proton lung MRI in free breathing has emerged as a novel technique for assessment of regional lung ventilation, but has yet not been validated with 129Xenon MRI (129Xe‐MRI), a direct visualization of ventilation in healthy volunteers, cystic fibrosis (CF), and chronic obstructive pulmonary disease (COPD) patients. Purpose: To compare regional ventilation and regional flow volume loops measured by noncontrast‐enhanced ventilation‐weighted phase‐resolved functional lung MRI (PREFUL‐MRI) with 129Xe‐MRI ventilation imaging and with lung function test parameters. Study Type: Retrospective study. Population: Twenty patients with COPD, eight patients with CF, and six healthy volunteers. Field Strength/Sequence: PREFUL and 129Xe‐MRI gradient echo sequences were acquired at 1.5T. Assessment: Coronal slices of PREFUL‐MRI (free breathing) and 129Xe‐MRI (single breath‐hold) were acquired on the same day, matched by their ventrodorsal position and coregistered for evaluation. Ventilation defect percentage (VDP) was calculated based on regional ventilation (RV), regional flow volume loops (RFVL), or 129Xe‐MRI with two different threshold methods. A combined VDP was calculated for RV and RFVL. Additionally, lung function testing was performed (such as the forced expiratory volume in 1 second [FEV1]) was used. Statistical Tests: The obtained parameters were compared using Wilcoxon tests, correlated using Spearman's correlation coefficient (r), and agreement between PREFUL and 129Xe‐MRI parameters was assessed using Bland–Altman analysis and Dice coefficients. Results: VDP measured by PREFUL and 129Xe were significantly correlated with both thresholding techniques (r = 0.62–0.69, P < 0.05 for all) and with lung function test parameters. Combined RV and RFVL PREFUL defect maps correlated with lung function testing (eg, with FEV1r = –0.87 P < 0.05), and showed better regional agreement to 129Xe‐MRI ventilation defects (Dice coefficient defect 0.413) with significantly higher VDP values (10.2 ± 27.3, P = 0.04) than either PREFUL defect map alone. Data Conclusion: Combined RV and RFVL PREFUL defect maps likely increase sensitivity to mild airway obstruction with increased VDP values compared to 129Xe‐MRI, and correlate strongly with lung function test parameters. Level of Evidence: 3 Technical Efficacy Stage: 2 [ABSTRACT FROM AUTHOR]

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 [ABSTRACT FROM AUTHOR]

Background: Perfusion-weighted (Qw) noncontrast-enhanced proton lung MRI is a promising technique for assessment of pulmonary perfusion, but still requires validation.Purpose: To 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 Type: Retrospective.Population: Twenty 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/sequence: For 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.Assessment: PREFUL-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 Tests: Obtained parameters were assessed using Pearson correlation and Bland-Altman analysis.Results: Qw-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 Conclusion: The automated PREFUL algorithm may allow for noncontrast-enhanced pulmonary perfusion assessment in COPD, CF, and CTEPH patients comparable to DCE-MRI. Level of Evidence 3 Technical Efficacy Stage 2 J. Magn. Reson. Imaging 2020;52:103-114. [ABSTRACT FROM AUTHOR]

Background Although measurable organic dysfunctions are frequently absent in pediatric patients with post-COVID-19 condition (PCC), this condition adversely affects quality of life. Free-breathing phase-resolved functional lung (PREFUL) MRI may be useful for assessing lung function in pediatric patients with PCC. Purpose To detect lung changes in children and adolescents with PCC compared with healthy control participants using PREFUL MRI. Materials and Methods In this single-center, prospective, cross-sectional study conducted between April 2022 and April 2023, children and adolescents (age ≤17 years) with PCC and age- and sex-matched healthy participants underwent MRI. Subgroup analysis was performed in participants with PCC who had cardiopulmonary symptoms. Regional ventilation, flow-volume loop correlation metric (FVL-CM), quantified perfusion, ventilation and perfusion defect percentages, and ventilation-perfusion ratios were compared between participants with PCC and controls using the Wilcoxon signed rank test. Correlation of imaging parameters with spirometry, heart rate, respiratory rate, and Bell score (fatigue severity) in participants with PCC was assessed using the Spearman rank correlation coefficient. Results The final study sample included 54 participants (27 participants with PCC and 27 matched control participants; median age, 15 years [IQR, 11-17 years]; 14 male participants). Twenty-one participants had cardiopulmonary symptoms. Participants with PCC had lower regional ventilation (median, 0.2 mL/mL [IQR, 0.1-0.2 mL/mL] vs 0.2 mL/mL [IQR, 0.2-0.2 mL/mL]; P = .047) and quantified perfusion (49 mL/min per 100 mL [IQR, 33-60 mL/min per 100 mL] vs 78 mL/min per 100 mL [IQR, 59-89 mL/min per 100 mL]; P < .001). Participants with PCC and cardiopulmonary symptoms had lower FVL-CMs (median, 0.99 arbitrary units [au] [IQR, 0.98-0.99 au] vs 0.99 au [IQR, 0.99-0.99 au]; P = .01) and higher ventilation defect (median, 7.6% [IQR, 4.5%-15.1%] vs 5.4% [IQR, 2.7%-7.1%]; P = .047) and perfusion defect percentage (median, 3.2% [IQR, 2.4%-4.2%] vs 2.3% [IQR, 1.8%-3.5%]; P = .02) compared with matched control participants. In participants with PCC, greater lung perfusion correlated with increased chronic fatigue severity (ρ = 0.48; P = .009) and higher ventilation-perfusion mismatch correlated with increased heart rate (ρ = 0.44; P = .02). Conclusion Free-breathing phase-resolved functional lung MRI-derived parameters helped identify a distinct phenotype of lung perfusion in children and adolescents with PCC and were correlated with heart rate and chronic fatigue severity. Clinical trial registration no. DRKS00028963 © RSNA, 2025 Supplemental material is available for this article. See also the editorial by Parraga and Svenningsen in this issue.

Background: Regional flow volume loop ventilation-weighted noncontrast-enhanced proton lung MRI in free breathing has emerged as a novel technique for assessment of regional lung ventilation, but has yet not been validated with 129 Xenon MRI ( 129 Xe-MRI), a direct visualization of ventilation in healthy volunteers, cystic fibrosis (CF), and chronic obstructive pulmonary disease (COPD) patients., Purpose: To compare regional ventilation and regional flow volume loops measured by noncontrast-enhanced ventilation-weighted phase-resolved functional lung MRI (PREFUL-MRI) with 129 Xe-MRI ventilation imaging and with lung function test parameters., Study Type: Retrospective study., Population: Twenty patients with COPD, eight patients with CF, and six healthy volunteers., Field Strength/sequence: PREFUL and 129 Xe-MRI gradient echo sequences were acquired at 1.5T., Assessment: Coronal slices of PREFUL-MRI (free breathing) and 129 Xe-MRI (single breath-hold) were acquired on the same day, matched by their ventrodorsal position and coregistered for evaluation. Ventilation defect percentage (VDP) was calculated based on regional ventilation (RV), regional flow volume loops (RFVL), or 129 Xe-MRI with two different threshold methods. A combined VDP was calculated for RV and RFVL. Additionally, lung function testing was performed (such as the forced expiratory volume in 1 second [FEV 1 ]) was used., Statistical Tests: The obtained parameters were compared using Wilcoxon tests, correlated using Spearman's correlation coefficient (r), and agreement between PREFUL and 129 Xe-MRI parameters was assessed using Bland-Altman analysis and Dice coefficients., Results: VDP measured by PREFUL and 129 Xe were significantly correlated with both thresholding techniques (r = 0.62-0.69, P < 0.05 for all) and with lung function test parameters. Combined RV and RFVL PREFUL defect maps correlated with lung function testing (eg, with FEV 1 r = -0.87 P < 0.05), and showed better regional agreement to 129 Xe-MRI ventilation defects (Dice coefficient defect 0.413) with significantly higher VDP values (10.2 ± 27.3, P = 0.04) than either PREFUL defect map alone., Data Conclusion: Combined RV and RFVL PREFUL defect maps likely increase sensitivity to mild airway obstruction with increased VDP values compared to 129 Xe-MRI, and correlate strongly with lung function test parameters., Level of Evidence: 3 TECHNICAL EFFICACY STAGE: 2., (© 2020 The Authors. Journal of Magnetic Resonance Imaging published by Wiley Periodicals LLC on behalf of International Society for Magnetic Resonance in Medicine.)