Objectives
To investigate ventilation in mild to moderate asthmatics and age-matched controls using hyperpolarized (HP)129Xenon-MR imaging and correlate findings with pulmonary function tests (PFTs).
Materials and Methods
This single-center, HIPAA-compliant prospective study was approved by our IRB. Thirty subjects (10 young asthmatics, 26±6 years; 3 males, 7 females; 10 older asthmatics, 64±6 years; 3 males, 7 females; 10 healthy controls) were enrolled. After repeated PFTs 1 week apart, subjects underwent 2 MRI-scans within 10 minutes, inhaling 1 liter volumes containing 0.5–1 liter of 129Xe. 129Xe ventilation signal was quantified by linear binning, from which the ventilation defect percentage (VDP) was derived. Differences in VDP among subgroups and variability with age was evaluated using one-tailed t-tests. Correlation of VDP with PFTs was tested using Pearson’s correlation coefficient. Reproducibility of VDP was assessed using Bland-Altman plots, linear regression (R2), intra-class correlation coefficient (ICC) and concordance correlation coefficient (CCC).
Results
VDP was significantly higher in young asthmatics vs. young healthy subjects (8.4±3.2% vs. 5.6±1.7%, P=.031), but not in older asthmatics versus age-matched controls (16.8±10.3% vs. 11.6±6.6%; P=.13). VDP was found to increase significantly with age (healthy: P=.05; asthmatics: P=.033). VDP was highly reproducible (R2=0.976, ICC=0.977, CCC=0.976) and significantly correlated with FEV1% (r=−0.42, P=.025), FEF25–75% (r=−0.45, P=.019), FEV1/FVC (r=−0.71, P<.0001), FeNO (r=0.69, P<.0001), and RV/TLC (r=0.51, P=.0067). Bland-Altman analysis showed a bias for VDP of −0.88±1.52 (FEV1%: −0.33±7.18).
Conclusion
129Xenon-MR imaging is able to depict airway obstructions in mild to moderate asthma and significantly correlates with PFTs.