The Rhea-study is a multicenter prospective diagnostic proof-of-concept study There is an unquestionable need for improved diagnostic approaches for (incidental) SVT. The researchers plan to evaluate the MRDTI technique, that has been shown to be accurate in other settings of difficult-to-diagnosis venous thrombosis, for the notoriously challenging diagnosis of incidental SVT. This study targets an important unmet need and will provide the basis for precision medicine for patients with SVT in the near future, i.e. the possibility of assessment of the age of the thrombus in patients with incidental SVT, which is of utmost importance for determination of the indication for anticoagulant therapy. If this hypothesis is proven true, i.e. sensitivity of MRDTI for SVT is indeed \>90%, the investigators will proceed with performing a randomized controlled outcome study in which patients with possible/probable chronic SVT with normal MRDTI test results and no other indications for anticoagulant therapy. These patients will be randomized between active therapeutically dosed anticoagulation versus no anticoagulation, to compare clinical outcome with regard to the occurrence of venous thromboembolism and/or Progressive symptomatic SVT as well as major bleeding.