General inclusion and exclusion criteria for both groups

Inclusion criteriaExclusion criteria
  • Proven CF as evidenced by positive sweat test or gene mutation

  • Ability to perform reproducible manoeuvres with spirometry

  • Ability to comply with MRI procedures

  • FEV1 ≥40% pred

  • Age ≥8 years

  • Chronic oxygen therapy

  • Isolation of Burkholderia cepacia

  • Lung transplantation

  • Participation in another trial

  • Any contraindications to MRI

  • Pregnancy

  • Not able or not willing to give consent

  • Allergic bronchopulmonary aspergillosis

CF: cystic fibrosis; MRI: magnetic resonance imaging; FEV1: forced expiratory volume in 1 s.