Deep venous thrombosis (DVT) is a venous reflux disorder caused by abnormal coagulation of blood in the deep vein, which usually occurs in the lower extremities. After thrombosis, venous valve function is often destroyed, causing lower limb swelling, ulcers and other congestive diseases, affecting the quality of life of patients; thrombus shedding is also easy to cause pulmonary embolism, serious cases can lead to sudden death. Therefore, the accurate diagnosis and curative effect evaluation of DVT are of great significance to the prognosis of patients. At present, the treatment of DVT includes systematic thrombolysis and catheter contact thrombolysis, among which oral drug thrombolysis has certain advantages in clinical application. However, in the process of thrombosis, the composition of thrombus is different in different periods, thus, defining the staging of thrombus plays an important role in the decision-making of drug treatment. In view of the high resolution of magnetic resonance imaging of soft tissue, thrombus can be directly imaged. Therefore, this project will take the staging diagnosis of deep venous thrombosis as the starting point. Through the development of magnetic resonance imaging, this paper tries to solve the problem of evaluating the therapeutic effect of deep venous thrombosis in clinic.

Deep venous thrombosis (DVT) is a venous reflux disorder caused by abnormal blood coagulation in the deep vein, which usually occurs in the lower extremities. DVT is common in patients with limb immobilization (such as after major orthopedic surgery), severe trauma, tumor, coma or long-term bedridden patients. After thrombosis, venous valve function is often destroyed, causing lower limb swelling, ulcers and other congestive diseases, affecting the quality of life of patients; thrombus shedding is also easy to cause pulmonary embolism, serious cases can lead to sudden death.

In the process of thrombosis, the components of thrombus are different in different stages. in the acute stage of thrombosis, the consumption of blood fibroses is less, mainly in the thrombolytic therapy of activating plasminogen; in the subacute and chronic phase of thrombosis, the consumption of fibrinolytic enzyme is more, anticoagulant therapy is needed to prolong the clotting time. Therefore, defining the staging of thrombus is the key to make a reasonable treatment plan and improve the therapeutic effect of DVT. The guidelines recommend that for patients with moderate or high likelihood of DVT, if two consecutive ultrasound examinations are negative, further X-ray venography, CT venography or magnetic resonance venous thrombosis direct imaging are recommended. Among them, magnetic resonance thrombus direct imaging depends on the content of methemoglobin in the body and will not produce radiation to the human body. it can not only accurately judge the thrombus in the pelvic and inferior vena cava, but also show the details of the changes in the vein wall or lumen. Therefore, magnetic resonance thrombus direct imaging has a certain potential in the differential diagnosis of acute, subacute and old thrombus. In this study, we will use magnetic resonance thrombus direct imaging to stage and judge the efficacy of drug treatment, in order to provide help for clinic.

Inclusion Criteria:

• More than 18 years old
• Suspected deep venous thrombosis of lower extremities
• No treatment related to deep venous thrombosis of lower extremities

Exclusion Criteria:

• Contraindication of magnetic resonance imaging
• Previous history of deep venous thrombosis
• History of allergy to magnetic resonance contrast agents

The people included in this study are patients suspected of deep venous thrombosis of lower extremities for the first time and should be older than 18 years old.