[Formation and migration of radioactive microemboli to the lung during radiovenography].

Two patients with lower extremity thrombophlebitis were studied by radionuclide venography with macroaggregated albumin labelled with 99mTc. Data analysis was performed with a new method. It generated sequential series of imagen (1-2 sec/frame) of the transit of the tracer through leg, thigh, and abdomen, allowing a more precise definition of temporal changes on regional radioactivity. This method rendered the first real evidence of the binding of the tracer to pre-existent venous thrombi, of the dislodgement of these and their gradual fragmentation during their transit to the lungs. The patients had no complaints during or after the study. Lung scanning, performed 24 hours later, showed slight alteration on regional lung perfusion in one case, and none in the other. It is concluded that radioactive microemboli to the lungs is a minor complication of radionuclide venography, which does not justify prevention. This could only nullify the sensitivity of the procedure.