The main objective of this trial is to prove that MRI - as the imaging modality without the use of ionizing radiation - can replace CT for structural and functional regional phenotyping of COPD. The identification of different COPD phenotypes, such as the "emphysema-type" and the "airway-type", is important because therapy and prognosis will be different. The medical problem addressed in this trial is the image-based phenotyping of COPD. The sensitivity and specificity of MRI will be compared to Lowdose-CT serving as the gold standard. MRI and CT of the lung will be performed in a multi-centre cohort of 625 COPD-patients from the main COSYCONET cohort. The reliability of the MRI results will be demonstrated. MRI phenotypes will be evaluated visually and using software with quantitative read-outs. The agreement of both will be determined. The additional information of MRI over CT will be assessed.

This prospective trial aims to phenotype COPD by using Imaging methods.The identification of different COPD phenotypes, such as the "emphysema-type" and the "airway-type", is important because therapy and prognosis will be different. Imaging might play a central role in diagnosing these phenotypes. So far computed tomography (CT) is regarded as the gold standard, but it involves ionizing radiation and lacks functional information. The medical problem addressed in this trial is the image-based phenotyping of COPD. The principal research question is whether magnetic resonance imaging (MRI) can replace CT for the characterization of COPD by "structural and functional phenotyping" on a regional basis. The sensitivity and specificity of MRI will be compared to CT serving as the gold standard. To achieve this goal, MRI and CT of the lung will be performed in a multi-centre cohort of 625 COPD-patients from the main Cosyconet cohort. Also, the reliability of the MRI results will be demonstrated. MRI phenotypes will be evaluated visually and using software with quantitative read-outs. The agreement of both will be determined. The additional information of MRI over CT will be assessed. A special focus will be to implement an image-based biomarker of pulmonary functional reserve derived from the MRI measurement of pulmonary perfusion, which will be correlated with results from pulmonary functions tests (e.g. the lung transfer factor for carbon monoxide (TLCO)) the 6-minute walking test (6-MWD), and extrapulmonary disease manifestations.

Inclusion Criteria:

• The population to be studied is determined by the main Cosyconet-cohort.

Key inclusion criteria:

• being included into the main cohort
• diagnosis of COPD (GOLD criteria)
• availability for repeated study visits
• male or female
• age > 40 years

Exclusion Criteria:

• Key exclusion criteria as determined by the main Cosyconet-cohort:
• having undergone lung surgery (e.g., lung volume reduction, lung transplant)
• moderate or severe exacerbation within the last 4 weeks prior to visit 1
• unable to understand the intention of the project
• lack of signed patient informed consent
• contraindications for MRI
• pregnancy

This Trial is fully embedded within the main cohort of the Cosyconet-Study: Impact of Systemic Manifestations/Comorbidities on Clinical State, Prognosis, Utilisation of Health care Ressources in Patients with COPD (COSYCONET), NCT01245933 ). Only patients included into the main study are asked to take part in this sub-trial which is not pharmaceutical and only has one arm including the expected number of patients (625) .

Pseudonymized Data from structured image reads will be transferred to the central COSYCONET data bank in Hannover. Application form for project proposals and data retrieval can be downloaded here: http://www.asconet.net/html/cosyconet/projects?clps4835\_49326291=1