DISCORDANT FINDINGS BETWEEN KRYPTON-81M GAS AND TC-99M LABELED ULTRAFINE AEROSOL LUNG VENTILATION SPECT IN 2 PATIENTS WITH IDIOPATHIC PULMONARY FIBROSIS

Technegas, a newly developed ultra-fine dry dispersion of Tc-99m label ed carbon with a particle size of approximately 5 nm to 20 nm, possess es the properties for lung ventilation imaging using SPECT. The author s observed a discrepancy between krypton-81m gas and technegas lung ve ntilation SPECT in two patients with idiopathic pulmonary fibrosis who demonstrated heterogeneously decreased distribution of technegas with out regions of high count density (focal hot spots) of tracer in their lungs in spite of the almost homogenous distribution of krypton-81m g as, This finding could be explained by the duration of radioactive gas inhalation. Technegas lung ventilation SPECT images reflected lung ve ntilation with tidal breathing, Conversely, Kr-81m gas lung ventilatio n SPECT images reflected not only lung ventilation, but also lung volu mes, These two radioactive agents for lung ventilation SPECT show diff erent findings.