Scintigraphy Of Acute Deep Venous Thrombus

Deep vein thrombosis (DVT) is a common occurrence. It is estimated that in the United States approximately 5 million patients experience one or more episodes of DVT each year, resulting in over 500,000 cases of pulmonary embolism and 100,000 deaths. Prompt treatment of acute thrombus is considered essential to initiate anticoagulation or thrombolytic therapy to prevent the serious consequences of pulmonary embolus. Radiographic evaluation of deep venous thrombus is performed both in symptomatic patients and in asymptomatic patients at high risk of venous thrombus, i.e., after orthopedic surgery. Contrast venography is considered the gold standard of diagnosis, but this invasive procedure is not routinely used. Duplex ultrasonography is probably the most common noninvasive technique used, followed by impedance plethysmography. Ultrasonography is thought to have excellent sensitivity and specificity in the thigh, but poor diagnostic accuracy below the knee. Both of the above techniques provide indirect evidence of thrombus by imaging an alteration in blood flow and thus cannot distinguish between acute and chronic thrombus. Direct detection of acute venous thrombus has been investigated using intravenously injected radiolabeled synthetic peptides that bind with high affinity to receptors expressed on activated platelets. In 1999, the FDA approved the radiopharmaceutical peptide apcitide (AcuTect™) for use in the scintigraphic imaging of acute venous thrombosis in the lower extremities in patients who have signs and symptoms of acute thrombophlebitis. Apcitide binds to glycoprotein IIb/IIIa fibrinogen receptors, which are expressed on the surface of activated platelets, thus making the radiopharmaceutical specific for acute, not chronic thrombus. <a id="