A 10-12 mCi 81Rb81mKr generator was connected to a specially designed 
short-period infusion set, to produce an equilibrium activity distribution 
in the right heart. This procedure was tested in 25 individuals to calculate 
the right ventricular ejection fraction (RVEF). On average 30 heart cycles 
were analyzed per study. No background activity from the left heart was 
visualized because of the radionuclide exhalation. The background from the 
lungs could be neglected, which is partially due to the ultrashort half-life 
of the nuclide (t 1/2=13s). Thus, an easy automatic procedure can be applied 
to delineate the ventricle and to calculate the RVEF. The data showed 
excellent reproducibility, when investigations were repeated. The method 
would benefit from use of higher activity generators.