Downstream Effects of Airway Mucus Plugs on 129Xenon MRI in Severe Asthma

This study is using a specialized MRI scan with inhaled xenon gas (129Xe MRI) to look at how mucus plugs in the airways of people with severe asthma affect lung function, and whether this improves after starting certain biologic asthma medications. **You may be eligible if...** - You are 18 to 65 years old - You have had a doctor's diagnosis of asthma for more than 1 year - Your blood eosinophil count is elevated (above 300 cells/μL), indicating an inflammatory type of asthma - You are about to start a biologic asthma medication (dupilumab, tezepelumab, or benralizumab) as part of your regular care - Your smoking history is minimal (fewer than 10 pack-years) and you have not smoked in the past 3 months **You may NOT be eligible if...** - You have had a respiratory infection in the past 4 weeks - Your BMI is above 30 - You are not starting one of the specified biologic asthma medications - You have had a recent significant medical procedure Talk to your doctor to see if this trial is right for you.