Radionuclide pulmonary arteriography.

: Radionuclide pulmonary arteriography offers a unique method for visualizing the main pulmonary artery and its major branches. Since the radioactive particles that are injected intravenously become lodged in the pulmonary capillaries and pre-capillary arterioles, there is no interference from the systemic circulation. Normally, the main pulmonary artery is visualized for no longer than 4 or 6 seconds; prolongation of the duration of visualization may be indicative of, for example, pulmonary hypertension and pulmonary embolism. The patency of the left and right pulmonary arteries may be determined and sites of occlusion identified.