Inclusion Criteria:  Age ≥18 years Biopsy or otherwise clinically proven thoracic malignant mass which is intended to be treated with radio(chemo)therapy Intention to treat with radio(chemo)therapy with incidental cardiac irradiation of at least 25Gy. A negative urine or serum pregnancy test within the two week interval immediately prior to imaging, in women of child-bearing age. Ability to provide written informed consent to participate in the study (for all components of the trial: imaging with cardiac PET/MR, blood sampling for plasma metabolomics and circulating DNA).  Exclusion Criteria:  Contraindication for MR as per current institutional guidelines. Contraindication for Gadolinium injection as per current institutional guidelines. Inability to lie supine for at least 45 minutes. Any patient who is pregnant or breastfeeding. Any patient with known hypersensitivity to 18F-FDG.