RADIONUCLIDE VENOGRAM

INDICATIONS:

1. Evaluation of upper extremity central venous vein patency.
2. Evaluation for deep venous thrombosis in patients in whom radiographic contrast material is contraindicated.
3. Detection of embolic source in patients with recurrent pulmonary embolism.
4. Patency study for IVC umbrella.
5. Evaluation of possible superior vena cava (SVC) syndrome.

PATIENT PREPARATION:

None.

RADIOPHARMACEUTICAL:

99mTc O4 or 99m-Tc-MAA is injected I.V. - 2 mCi to each foot or 10 mCi to each upper extremity for SVC and upper extremity evaluation. In the case of a lower extremity venogram, a lung scan is also performed.

SCANNING TIME:

Variable - depending on ease of venous access. Once injected, the patient is imaged immediately and the scan time can take up to 30 minutes. Additional time is required if Tc-99m MAA is used and a lung perfusion scan is performed.

OTHER CONSIDERATIONS:

1. Tc-99m MAA is the same agent used for the perfusion lung scan; both studies can, therefore, be obtained without additional injection.
2. Acute and chronic thrombus cannot be easily differentiated.
3. In general, the accuracy of the radionuclide venogram is good in comparison to contrast venography (76-96%). Morphologic detail is poor, however, and mural thrombosis without significant obstruction will often cause a false negative result.
4. In the lower limbs, this study best evaluates the thigh and pelvic veins; accuracy is poor for the venous system below the knee (calf).

RATIONALE:

The normal venogram shows flow through tibial, popliteal, femoral, and iliac veins. The Tc-99m MAA then travels through the heart and into the pulmonary bed - allowing lung perfusion imaging. Persistent flow defects, abnormal collateral flow and/or non-visualization of a major vein are positive findings. Delayed clearance or tracer hang-up will be seen in areas of phlebitis. (Tourniquets are used to differentiate superficial from deep venous flow).