I can certainly relate to your problem. There are a few things that work for me. However I have Bronchiectasis and not Asthmatic Bronchitis. Not sure if what I do will work for you. Since most of my productive coughing happens in the late morning I try to schedule the MRI for early morning or afternoon if possible, and I will also do my daily postural drainage and manual chest percussion a good hour before the MRI if at all possible to get up most of the sputum. And I know you are not supposed to suppress a productive cough, but I will take a regular dose of codeine cough syrup about 30 minutes before the MRI, on an empty stomach so as to get quick absorption. You will have to talk your Dr into an Rx for that. Sue @sueinmn may be able to advise you better with this. Good luck, Bill