Combined scintigraphic study of the lung: what does the inhalation study add?

In 175 patients the results of combined isotope studies i. e. inhalation and perfusion scintigraphy were compared with those of chest x-ray. The absorbed radiation dose due to the inhalation study calculated for whole body was 3 mrad/500 muCi, lungs 380 mrad/500 muCi, ovaries 0.3 mrad/500 muCi and testes 0.03 mrad/500 muCi. In 44 of our cases the isotope studies suggested the presence of a vascular occlusion, not detectable on the x-ray film in 36 cases. In the remaining 8 cases the inhalation study was found to add to the precision of the diagnosis. In nearly all other cases it was not found to have any diagnostic value.