Radionuclide venography: significance of delayed washout; visualization of the saphenous system.

Venograms were obtained on dogs in which venous thrombosis had been surgically induced. Radionuclide venograms, obtained after injection of 99mTc-labeled microspheres or macroaggregated albumin, showed decreased radioactivity over the areas of venous thrombosis and increased radioactivity over areas of venous stasis. Scintigrams of veins excised after an injection of labeled particles did not delineate thrombi, areas of crush-injured vein, or the venous valves. Delay in the washout of radioactivity on a venogram indicates stasis due to impeded venous flow in the area of thrombosis. A modified technique was developed to obtain simultaneous images of the superficial and deep veins of the leg. Visualization of the superficial veins not only permits detection of superficial abnormalities, but also assists interpretation of the venographic observations of the deep veins.