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

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 Xenon MRI ( 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 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 Xe-MRI gradient echo sequences were acquired at 1.5T.

ASSESSMENT

Coronal slices of PREFUL-MRI (free breathing) and 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 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 ]) was used.

STATISTICAL TESTS

The obtained parameters were compared using Wilcoxon tests, correlated using Spearman's correlation coefficient (r), and agreement between PREFUL and Xe-MRI parameters was assessed using Bland-Altman analysis and Dice coefficients.

RESULTS

VDP measured by PREFUL and 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 r = -0.87 P < 0.05), and showed better regional agreement to 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 Xe-MRI, and correlate strongly with lung function test parameters.

LEVEL OF EVIDENCE

3 TECHNICAL EFFICACY STAGE: 2.