Quantitative in vivo and in vitro comparison between radiolabelled colloids, biomolecules and blood cells in their ability to diagnose deep venous thrombosis.

Three radiopharmaceutical groups (colloids, specific biomolecules and blood cells) and a control group were investigated with regard to their ability to rapidly diagnose deep venous thrombosis in an experimental rabbit model. An artificial thrombus was induced in the jugular vein and the radiopharmaceuticals were injected either homolaterally or contralaterally relative to the thrombus. The accumulation of the radioactivity in the thrombus 30 min after the induction was determined in vivo from scintillation camera images. After dissection of the jugular vein, the radioactivity of the thrombus was measured in vitro. None of the investigated radiopharmaceutical groups showed any marked high thrombus uptake after contralateral injections, not even the groups that consisted of substances known to be actively involved in coagulation and fibrinolysis. The results exclude a high degree of specific interaction between the radiopharmaceuticals and the thrombus in our model. After homolateral injection only colloids and reduced 99Tcm-pertechnetate showed a high thrombus uptake, thus also excluding a specific binding to thrombus. This investigation shows that none of the specific radiopharmaceuticals had a greater ability to accumulate in the thrombus than the colloids, and it is therefore suggested that the clinical usefulness is due to other mechanisms, like circulatory changes secondary to the DVT.