Comparison of technetium-99mC and phytate aerosol in ventilation studies

The image quality obtained with technetium-99mC aerosol (Technegas) was evaluated and compared with that obtained with 99mTc-phytate aerosol generated by a jet nebulizer. Fifty patients underwent ventilation scanning after inhalation of each aerosol (mean interval of 3 days). Four views (anterior, posterior, left and right posterior oblique) were recorded with 200 k precounts. Both sets of images were blindly compared for (i) qualitative evaluation of images, (ii) quantitation of penetration (PI) and heterogeneity (HI) indices and (iii) assessment of ventilation state. Peripheral penetration was the same in 64% of cases, greater with 99mTc-C in 27% and greater with 99mTc-phytate in 9%. The use of 99mTc-C led to fewer and less intense foci of bronchial or gastric activity. The differences for 99mTc-C and 99mTc-phytate, respectively, between mean PI (0.78 vs. 0.70) and HI (15 vs. 18) were not significant. Consideration of all the parameters indicates the overall superiority of 99mTc-C. The final interpretation of the lung ventilation scans was, however, similar with both tracers.