T1-weighted DANTE-SPACE Angiography Of Deep Venous Thrombosis In Lower Extremities

Background:Deep venous thrombosis(DVT)is a common disease occurring in the deep veins of the lower extremities.The incidence rate is over 1 per thousand,which is the third major vascular disease of cerebrovascular disease and coronary atherosclerotic heart disease.In addition to the swelling,pain and ulceration of lower limbs caused by deep venous thrombosis,50%of patients may be complicated with pulmonary embolism,which seriously endangers the lives of patients.If DVT is not effectively treated in the early stage of acute thrombosis,thromboembolization leads to post-thrombotic syndrome,which seriously affects the work and quality of life of patients.Therefore,the accurate diagnosis and treatment of DVT is of great significance to prevent the occurrence of pulmonary embolism,reduce the suffering of patients and reduce the burden of society and patients'families.Intravenous thrombolysis,interventional thrombolysis and venous anticoagulation therapy are the most effective treatments for DVT patients.Thrombosis in different stages has different choice of venous thrombolysis,interventional thrombolysis and venous anticoagulation therapy.Therapeutic effect and prognosis are different.Accurate display of the distribution of thrombosis and judgment of the stages of thrombosis are the key to choose a reasonable treatment plan.Intravenous thrombolysis is a good choice for newly formed large area thrombosis,but it is not suitable for non-acute thrombosis.In acute and sub-acute stage of thrombosis,the consumption of blood fibrinolytic enzymes is less,and the thrombolysis treatment mainly based on activation of plasminogen.In subacute and chronic stage of thrombosis,the consumption of blood fibrinolytic enzymes is more,and the anticoagulation treatment mainly based on prolonging the clotting time.If the distribution and staging of thrombus can not be accurately determined,simple intravenous thrombectomy,thrombolysis and anticoagulation therapy are not ideal or accompanied by serious complications.At present,DSA is still the golden standard for the diagnosis of DVT.It can accurately judge whether thrombus exists or not and its distribution.However,this method is invasive and has certain risks,and it is only used in the course of interventional therapy.Ultrasound is widely used in clinical examination of DVT because of its advantages of non-invasiveness,convenience,simplicity and low cost.However,this method relies on the skills and experience of ultrasound doctors,and has a small imaging field,which can easily lead to missed diagnosis or even misdiagnosis of DVT.It is difficult to accurately measure the size of thrombus.For DVT patients with pelvic venous thrombosis,lower limb wounds,plaster fixation,obesity and edema,the application of ultrasound is limited and the accuracy decreases.At the same time,there are many variations in the development of lower limb veins.The limb has double vein structure,which is easy to miss the diagnosis of venous thrombosis,and ultrasound can not distinguish acute and chronic thrombosis[9],which affects the choice of treatment options.Magnetic resonance imaging(MRI)has many advantages,such as good soft tissue contrast,multi-parameter scanning,full field imaging and no radiation damage.Many MRI techniques have been applied to clinical examination of DVT.There are three kinds of magnetic resonance techniques commonly used in clinical diagnosis of DVT:Contrast Enhanced Magnetic Resonance Venography(CE-MRV),balanced Steady-state Free Precession(bSSFP)and magnetic resonance direct Thrombus imaging(MRDTI).CE-MRV is often used to judge the presence and distribution of thrombus.The sensitivity,specificity and accuracy of CE-MRV are better than that of ultrasound.However,CE-MRV examination needs to accurately estimate the circulation time of target blood vessels.The imaging time window 1s short and the scanning operation is difficult.The use of contrast agent not only increases the cost of examination,but also has the risk of complications and can not be used.In patients with severe renal insufficiency and pregnant women,the staging of thrombosis can not be carried out at the same time.BSSFP technology is to use its natural bright blood effect,without contrast agent,so that the blood vessels in the lumen of blood flow is high signal,thrombosis is low signal,in determining whether the blood vessels occluded,and CE?MRV have the same effect.However,this technique can only be used for rapid screening of DVT,and the size of thrombus is not clearly displayed,and the staging of thrombus can not be judged,so its clinical practical value is not high.MRDTI is a T1 weighted gradient echo imaging technology based on the pulse of turn recovery preparation.It uses direct paramagnetic characteristics of massive hemoglobin hemoglobin in acute late and subacute thrombus,and has a high sensitivity and specificity.However,the technology is too dependent on methemoglobin content to shorten the T1 relaxation time and make the thrombus hyperintense.Therefore,it can only diagnose acute late or subacute thrombosis of high methemoglobin content,but it is not good for the early and chronic DVT with low methemoglobin content.Since about 50%of patients have no symptoms or symptoms when DVT occurs,they can only subjectively infer that DVT staging is strong and inaccurate.Therefore,there is an urgent need for objective imaging techniques to diagnose DVT staging.Studies have shown that the concentration of methemoglobin in venous thrombosis will be changed at different stages of thrombus evolution.The short T1 effect of venous thrombosis is linearly related to the content of methemoglobin in the thrombus[16].Because the content of methemoglobin in different stages of thrombus evolution is different,the content of methemoglobin is less in acute phase,while the content increases in subacute and chronic phases,and then decreases.Therefore,at different stages of thrombus,the change of the content of methemoglobin in the magnetic field will directly lead to the change of signal intensity of T1 weighted magnetic resonance imaging.Therefore,T1 stage weighted magnetic resonance imaging can indirectly infer the DVT stage.However,the velocity of venous blood flow is very slow,especially in the lumen where severe venous thrombosis occurs.The existing T1-weighted magnetic resonance imaging technology still can not suppress the slow flow of blood signals very well,and the obtained thrombosis signals are easily contaminated by blood flow signals.So far,there is no magnetic resonance imaging technology that can provide objective criteria for DVT staging by using the above mechanism.Objective:This study used the T1 weighted DANTE-SPACE angiography sequence developed and designed in 2018 by Professor XieGuoxi of the Shenzhen advanced technology research institute of the Chinese Academy of Sciences.The purpose of this study was to investigate the venous blood flow inhibition,venous wall and venous thrombosis in the sequence,and the changes of DVT expression and thrombus signal intensity in T1WI caused by the evolution of methemoglobin in the thrombus.Regularly,according to the relative signal intensity of thrombus and muscle at the same level,we infer acute and subacute venous thrombosis,and compare the advantages and disadvantages of T1-weighted DANTE-SPACE vascular wall imaging sequence and ultrasound examination.It provides a new and safe imaging technology for DVT clinical examination,and benefits DVT patients.Materials and methods:Study 1 collected 23 healthy volunteers from May 2018 to December 2018,13 males and 10 females,aged 31-68 years,with an average age of 47 years,without any clinical symptoms.Ultrasound examination showed that venous thrombosis in lower extremities was negative.Study 2 collected 28 patients with definite history of sudden lower extremity venous thrombosis from May 2018 to May 2019,including 16 males and 12 females,aged 27-75 years with an average age of 49 years.All patients were confirmed by ultrasonography.The onset time was less than 14 days in 15 cases and less than 28 days in 13 cases.Study 3 collected 48 patients with lower extremity venous thrombosis from May 2018 to May 2019,27 males and 21 females,aged 27-90 years,with an average age of 53 years,all confirmed by ultrasonography.Clinical symptoms include cllronic swelling of lower limbs,persistent pain and ulceration of lower limbs.Using SIEMENS skyro 3.0T superconducting magnetic resonance imaging system,all patients were supine position,foot advanced,scanned with two individual coils,two coils placed overlapped,overlapped about 3cm,scanning range from iliac vein to bilateral calf veins.T1-weighted DANTE-SPACE angiography was performed in three segments.After image optimization in 2018,the scanning time of three segments is 4 minutes 30 seconds,3 minutes 22 seconds and 3 minutes,totaling 10 minutes 57 seconds.A kind ofThe results of image examination were observed by double-blind method,and were independently completed by two radiologists with Deputy professional titles.All the original images are transmitted to the workstation for image mosaic,maximum density projection and surface reconstructionThe image quality of external iliac vein,common femoral vein,deep femoral vein,femoral vein,popliteal vein,anterior tibial vein,posterior tibial vein,peroneal vein and intermuscular vein were recorded respectively.The distribution of thrombus was observed.The muscle signal intensity was measured at the same level and the relative signal intensity of thrombus/muscle was calculatedResults:1.23 healthy volunteers received T1-weighted DANTE-SPACE vascular wall imaging.Doctor A and Doctor B scored 1 on image quality.The main vessels were external iliac vein,anterior tibial vein,posterior tibial vein and popliteal vein.Vascular artifacts were more serious.Doctors A and B scored the image quality of healthy volunteers with good consistency and no statistical difference2.Among 48 patients with lower extremity venous thrombosis,35 cases occurred on the left side,23 cases on the right side and 10 cases on both sides.T1-weighted DANTE-SPACE vascular wall imaging showed a good effect in inhibiting the blood flow around the thrombus.There was no statistical difference in the scores of venous patency in patients with lower extremity venous thrombosis3.28 patients with a clear history of sudden lower extremity venous thrombosis,15 in acute stage,67 in venous thrombosis,13 in subacute stage,78 in venous thrombosis.Thrombosis in acute stage showed high signal shadows at the edge of the great vessels,iso-signal at the center,clear boundary of thrombus,high signal migration to the center in subacute early stage,high signal shadows in subacute late stage,and low signal of thrombus in subacute stage.The signal intensities of thrombus in acute and subacute phase were 332.94±75.28)and 214±42.49),respectively.The signal intensities of muscle were 117.75±18.75),121.01±17.78),and the relative signal intensities were 2.86(+0.81)and 1.87±0.45),respectively.There was a significant difference in the relative signal intensities between the two groups.With the relative signal intensity of 2.22 as the threshold,the area under ROC curve was 0.871.The diagnostic sensitivity and specificity of acute and subacute deep venous thrombosis of lower extremities were 83.9%and 77.2%,respectively.4.48 patients with lower extremity venous thrombosis,3 of them had T1-weighted DANTE-SPACE vessel wall imaging,which indicated acute or subacute venous thrombosis of calf intermuscular vein.Ultrasound examination was negative.8 patients had ultrasound-induced thrombosis of anterior tibial vein,posterior tibial vein,peroneal vein and calf intermuscular vein,and magnetic resonance examination was negative.Conclusion:1.T1-weighted DANTE-SPACE angiography can effectively suppress venous blood flow signals while retaining thrombus signals,avoid the interference of venous blood flow signals on the thrombus signals,and clearly display venous vessels.2.According to the changes of T1WI signal intensification caused by the content of methemoglobin in the evolution of thrombus,T1 weighted DANTE-SPACE angiography can infer the deep vein thrombosis of the lower extremities in the early subacute stage and subacute stage according to the relative signal intensity of thrombus/muscle,combined with the morphology and signal changes of the thrombus,and provide an objective imaging basis for formulating reasonable interventional thrombolytic therapy.3.T1-weighted DANTE-SPACE vascular wall imaging has high spatial resolution.Small perforator vessels,great saphenous vein acute subacute early and subacute deep venous thrombosis of lower extremity are better than ultrasound,while chronic thrombosis is inferior to ultrasound.