Radionuclide venography and labeled platelets in deep venous thrombosis.

99mTc-labeled macroaggregated albumin, 99mTc-labeled red blood cell, and 99mTc human serum albumin blood pool venography are simple, noninvasive imaging procedures that provide indirect evidence of deep vein thrombosis. These techniques rely on alterations in the normal venous anatomy. They do not determine the cause of venous obstruction and/or altered anatomy and cannot differentiate between acute and chronic deep venous thrombosis. In vitro labeled platelet scintigraphy provides direct evidence of active or acute thrombosis. Unfortunately, this technique requires a labor-intensive, lengthy labeling process and has a high number of false-negative results in patients who receive heparin therapy.