Hyperpolarized 3 He and 129 Xe MRI: Differences in asthma before bronchodilation

Purpose To compare hyperpolarized helium‐3 ( 3 He) and xenon‐129 ( 129 Xe) MRI in asthmatics before and after salbutamol inhalation. Materials and Methods Seven asthmatics provided written informed consent and underwent spirometry, plethysmography, and MRI before and after salbutamol inhalation. 3 He and 129 Xe ventilation defect percent (VDP) and ventilation coefficient of variation (COV) were measured. To characterize the airways spatially related to ventilation defects, wall area percent (WA%) and lumen area (LA) were evaluated for two subjects who had thoracic x‐ray computed tomography (CT) acquired 1 year before MRI. Results Before salbutamol inhalation, 129 Xe VDP (8 ± 5%) was significantly greater than 3 He VDP (6 ± 5%, P = 0.003). Post‐salbutamol, there was a significant improvement in both 129 Xe (5 ± 4%, P < 0.0001) and 3 He (4 ± 3%, P = 0.001) VDP, and the improvement in 129 Xe VDP was significantly greater ( P = 0.008). 129 Xe MRI COV (Pre: 0.309 ± 0.028, Post: 0.296 ± 0.036) was significantly greater than 3 He MRI COV (Pre: 0.282 ± 0.018, Post: 0.269 ± 0.024), pre‐ ( P < 0.0001) and post‐salbutamol ( P < 0.0001) and the decrease in COV post‐salbutamol was significant ( 129 Xe, P = 0.002; 3 He, P < 0.0001). For a single asthmatic, a sub‐segmental 129 Xe MRI ventilation defect that was visible only before salbutamol inhalation but not visible using 3 He MRI was spatially related to a remodeled fourth generation sub‐segmental airway (WA% = 78%, LA = 2.9 mm 2 ). Conclusion In asthma, hyperpolarized 129 Xe MRI may help reveal ventilation abnormalities before bronchodilation that are not observed using hyperpolarized 3 He MRI. J. Magn. Reson. Imaging 2013;38:1521–1530. © 2013 Wiley Periodicals, Inc.