Hyperpolarized Helium 3 MRI in Mild-to-Moderate Asthma: Prediction of Postbronchodilator Reversibility.

Background Longitudinal progression to irreversible airflow limitation occurs in approximately 10% of patients with asthma, but it is difficult to identify patients who are at risk for this transition. Purpose To investigate 6-year longitudinal changes in hyperpolarized helium 3 (He) MRI ventilation defects in study participants with mild-to-moderate asthma and identify predictors of longitudinal changes in postbronchodilator forced expiratory volume in 1 second (FEV) reversibility Materials and Methods Spirometry and hyperpolarized He MRI were evaluated in participants with mild-to-moderate asthma in two prospectively planned visits approximately 6 years apart. Participants underwent methacholine challenge at baseline (January 2010 to April 2011) and pre- and postbronchodilator evaluations at follow-up (November 2016 to June 2017). FEV and MRI ventilation defects, quantified as ventilation defect volume (VDV), were compared between visits by using paired tests. Participants were dichotomized by postbronchodilator change in FEV at follow-up, and differences between reversible and not-reversible groups were determined by using unpaired tests. Multivariable models were generated to explain postbronchodilator FEV reversibility at follow-up. Results Eleven participants with asthma (mean age, 42 years ± 9 [standard deviation]; seven men) were evaluated at baseline and after mean 78 months ± 7. Medications, exacerbations, FEV (76% predicted vs 76% predicted; = .91), and VDV (240 mL vs 250 mL; = .92) were not different between visits. In eight of 11 participants (73%), MRI ventilation defects at baseline were at the same location in the lung at follow-up MRI. In the remaining three participants (27%), MRI ventilation defects worsened at the same lung locations as depicted at baseline methacholine-induced ventilation. At follow-up, postbronchodilator FEV was not reversible in six of 11 participants; the concentration of methacholine to decrease FEV by 20% (PC) was greater in FEV-irreversible participants at follow-up ( = .01). In a multivariable model, baseline MRI VDV helped to predict postbronchodilator reversibility at follow-up ( = 0.80; < .01), but PC, age, and FEV did not ( = 0.63; = .15). Conclusion MRI-derived, spatially persistent ventilation defects predict postbronchodilator reversibility 78 months ± 7 later for participants with mild-to-moderate asthma in whom there were no changes in lung function, medication, or exacerbations. © RSNA, 2019 See also the editorial by Stojanovska in this issue.