Flow Volume Loop and Regional Ventilation Assessment Using Phase‐Resolved Functional Lung (PREFUL) MRI: Comparison With ¹²⁹Xenon Ventilation MRI and Lung Function Testing

Abstract

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 FEV1 r = –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

Repeatability of dynamic 3D phase‐resolved functional lung (PREFUL) ventilation MR Imaging in patients with chronic obstructive pulmonary disease and healthy volunteers

“…Recently, 2D PREFUL VDP was validated to hyperpolarized 129 Xe imaging with very promising results. 23 Future studies are necessary to address the mentioned limitations.…”

“…Repeatability and validation studies of 2D PREFUL to reference standards have been performed to facilitate the use of 2D PREFUL in clinical routine. [20][21][22][23] Recently, 3D PREFUL has been developed to assess dynamic ventilation of the whole lung in an 8-minute acquisition, and the preliminary feasibility results in 16 study participants including patients with asthma, CF, and COPD have been presented. 24 However, the repeatability of ventilation parameters derived from 3D PREFUL, which is necessary to know prior to its use in clinical settings, has not been assessed.…”

Editorial for “Flow Volume Loop and Regional Ventilation Assessment Using Phase Resolved Functional Lung (PREFUL) MRI: Comparison With 129Xenon Ventilation MRI and Lung Function Testing”

“…Spatial and quantitative biomarker agreement with hyperpolarized gas MRI have been some of the primary goals of functional 1 H lung MRI development to date 4–6 . In this issue of JMRI, Kaireit et al 7 derived PREFUL MRI regional ventilation as well as regional flow‐volume loop maps and compared with 129 Xe MRI static ventilation and clinical lung function tests. Multiple PREFUL metrics were generated, but the primary assessment was the ventilation defect percent (VDP) for both PREFUL and 129 Xe.…”

“…A unique addition of this work 7 was the regional comparison of PREFUL regional ventilation and flow‐volume loop with 129 Xe ventilation defects. This analysis suggested that the combination of PREFUL flow‐volume loop with regional ventilation approaches may be more sensitive to partially obstructed or slow‐filling lung units.…”

“…It is important to acknowledge that PREFUL MRI requires considerable postprocessing to generate any regional lung function maps and biomarkers; streamlined and standardized quantification pipelines will be invaluable to disseminate this method. With Kaireit et al's validation work 7 and future efforts to streamline postprocessing, PREFUL MRI has the potential to make functional lung MRI more accessible worldwide, and, hopefully, generate broader impact on patient care.…”