N-isopropyl-p[123I]iodoamphetamine, a new agent for lung imaging studies.

N-isopropyl-p[123I]iodoamphetamine, originally designed for brain scintigraphy, has been found to be retained by the normal lung and to produce excellent camera images. Ten patients with gross abnormalities on their chest radiographs due to lung cancer have been studied with this drug. The diseased parts of the lung consistently showed less uptake and these defects matched those obtained with microspheres labelled with technetium-99m, indicating that 123I-iodoamphetamine has the characteristics of a perfusion tracer. In five out of the 10 patients studied sequential studies showed that improved iodoamphetamine uptake was encountered shortly after a favourable response to radiotherapy and reduced uptake was seen in congruence with the radiation field at a later stage. This first clinical demonstration indicates that the retention of 123I-iodoamphetamine could be a sensitive marker for pulmonary vascular integrity and a useful new tool to identify the extent of disease where the pulmonary circulation is the initial site of the disorder.