Hyperpolarized 3He and 129Xe MRI: Differences in Asthma Before Bronchodilation

PurposeTo compare hyperpolarized helium-3 (He-3) and xenon-129 (Xe-129) MRI in asthmatics before and after salbutamol inhalation. Materials and MethodsSeven asthmatics provided written informed consent and underwent spirometry, plethysmography, and MRI before and after salbutamol inhalation. He-3 and Xe-129 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. ResultsBefore salbutamol inhalation, Xe-129 VDP (8 5%) was significantly greater than He-3 VDP (6 +/- 5%, P = 0.003). Post-salbutamol, there was a significant improvement in both Xe-129 (5 +/- 4%, P < 0.0001) and He-3 (4 +/- 3%, P = 0.001) VDP, and the improvement in Xe-129 VDP was significantly greater (P = 0.008). Xe-129 MRI COV (Pre: 0.309 +/- 0.028, Post: 0.296 +/- 0.036) was significantly greater than He-3 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 (Xe-129, P = 0.002; He-3, P < 0.0001). For a single asthmatic, a sub-segmental Xe-129 MRI ventilation defect that was visible only before salbutamol inhalation but not visible using He-3 MRI was spatially related to a remodeled fourth generation sub-segmental airway (WA% = 78%, LA = 2.9 mm(2)). ConclusionIn asthma, hyperpolarized Xe-129 MRI may help reveal ventilation abnormalities before bronchodilation that are not observed using hyperpolarized He-3 MRI. J. Magn. Reson. Imaging 2013;38:1521-1530. (c) 2013 Wiley Periodicals, Inc.