Left Heart Imaging Following C15O2 Inhalation

Cyclotron produced C15O2, administered by inhalation, has been used to obtain gated images of the left heart in systole and diastole. The inhaled gas rapidly crosses the alveolar membrane and labels the water fraction of the lung capillary blood which then proceeds directly into the left heart. This method of administration has the advantage of being totally non-invasive; because there is no venopuncture involved, sterility and non-pyrogenicity of the radiopharmaceutical do not have to be established. A standard commercially available scintillation camera (with high energy collimator) interfaced to a minicomputer was used for this study. Improved visualization of the left ventricle is obtained because of absence of activity in the right heart and low internal absorption of the 511 keV annihilation radiation.