Krypton-81m.
D003201:Computers; D006801:Humans; D007726:Krypton; D008171:Lung Diseases / Q000000981:diagnostic imaging*; D008176:Lung Volume Measurements; D008722:Methods; D008954:Models, Biological; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging; D011868:Radioisotopes; D011876:Radionuclide Generators; D011877:Radionuclide Imaging; D012119:Respiration; D012413:Rubidium; D013667:Technetium; D014692:Ventilation-Perfusion Ratio; D014980:Xenon Radioisotopes
D011868:Radioisotopes; D014980:Xenon Radioisotopes; D007726:Krypton; D013667:Technetium; D012413:Rubidium