I-123 iodoamphetamine lung scanning in patients with ventilation-perfusion mismatching.

I-123 IMP is a nonparticulate agent and becomes trapped by endothelial membranes in the pulmonary capillaries. Using I-123 IMP, the authors studied six patients with ventilation-perfusion mismatch. Three of six patients had pulmonary thromboembolism, and three had pulmonary hypertension. In comparison with conventional perfusion lung scanning using Tc-99m MAA, defect sizes visualized by I-123 IMP were smaller in all patients. I-123 iodoamphetamine is a useful agent for assessing the perfusion of pulmonary arterial microvasculature which Tc-99m MAA fails to penetrate.