keywords AIRWAY WALL THICKNESS Asthma BRONCHIAL THERMOPLASTY EXERCISE-INDUCED BRONCHOCONSTRICTION HE-3 MAGNETIC-RESONANCE HYPERPOLARIZED HE-3 Life Sciences & Biomedicine OBSTRUCTIVE PULMONARY-DISEASE PROOF-OF-CONCEPT RESOLUTION COMPUTED-TOMOGRAPHY Respiratory System SEGMENTAL ALLERGEN CHALLENGE Science & Technology VENTILATION HETEROGENEITY airways magnetic resonance imaging ventilation heterogeneity