The ABPA is responsible for pulmonary exacerbations in chronic bronchial diseases. The treatment of ABPA consists in systemic corticosteroids and anti fungal therapy, which can have severe side effects. The diagnosis is difficult, based on several but non-specific characteristics. One of the radiologic abnormalities on CTscan could be more specific : high attenuation in impacted mucus, but this sign is found in about 30% of cases. Recent articles and investigators experience seem to demonstrate that MRI could provide an interesting tool for ABPA diagnosis, studying the signal of bronchial impactions. The aim of the study is to describe the MRI characteristics of patients with ABPA and compare the results with those obtained by CTscan, and in order to determine if there is a specific signal of impaction in ABPA.