EVALUATION OF THE ACCURACY AND PRECISION OF LUNG AEROSOL DEPOSITION MEASUREMENTS FROM PLANAR RADIONUCLIDE IMAGING USING SIMULATION

Planar images of known, theoretical distributions of radioaerosol in t he lung have been simulated using lung models derived from magnetic re sonance studies on human subjects. Total lung activity was evaluated f rom the simulated images together with the absolute penetration index (PI) and a relative value expressed as a fraction of that in a simulat ed ventilation image. The accuracy and precision of these measurements were calculated by comparison with the true values used in the simula tion. Total activity was assessed with systematic errors within 5% and precision within 6.5%. Measured PIs varied only slowly with true PI a nd inter-model variation masked changes between measurements on the di fferent distributions. The relative PI reduced inter-model variation a nd provided significant differences between all the distributions. PI was significantly affected by misalignment of the lung region of inter est. The conducting airways deposition fraction (CADF) used in the sim ulation correlated linearly with the fractional activity in a central lung region, allowing CADF to be estimated with a precision of 21%.