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Results: divided into 6 bins with a width of 1SD. The resulting maps readily permitted defining VDR as< mean-2SD, low-intensity regions (LIR,-2SD to-1SD) and high-intensity regions (HIR,+ 1SD to+ 2SD). For young controls these comprised volumetric fractions of VDR= 2.6±1.8%, LIR= 17.5±5.7%, HIR= 16.7±3.3%. The methods were applied to patients with mild intermittent asthma before and after albuterol treatment and a patient with bronchial stenosis before and after stenting (Figure). In the two patients with mild intermittent asthma, baseline Xe 129

MRI showed increased VDR (red), LIR (orange) and HIR (blue). After albuterol, there was improvement in ventilation distribution regardless of FEV1 response. In the patient with bronchial stenosis, ventilation distal to the stenosis improved after stenting and HIR reduced in the contralateral lung even though FEV1 did not change.