RADIOAEROSOL TC-99M-DTPA CHARACTERIZATION PRODUCED BY SOME NEBULIZERS

1. The radioacrosol Tc-99m-DTPA produced by jet and ultrasonic nebulizers was characterized by measuring the median mass diameter (MMD) and geometric standard deviation (sigma(g)) and these characteristics were interpreted in terms of the aerodynamic principles of inertial impactation. 2. Jet nebulizers of the same model, with different outflows (NS(A) = 0.14 ml/min; NS(B) = 0.24 ml/min and NS(C) = 0.40 ml/min) showed different radioacrosol mass distribution, with MMD (NS(C)) > MMD (NS(A)). The ultrasonic nebulizer US-1000 from Narcosul, which is operated with an air flow of 2 l/min and frequency of 1.6 MHz, generated radioaerosol with MMD = 2.40 mum, higher than that obtained with most of the jet nebulizers evaluated (NS(A) = 1.50 mum; NS(B)1V = 1.40 mum; NS(B)2V = 1.20 mum and PITT#1 = 0.80 mum), and the ultrasonic nebulizer presented the highest outflow of the nebulized solution (1.15 ml/min). 3. Connecting one or two impactation reservoirs to the NS(B) jet nebulizer modified the mass distribution, which became significantly narrower for NS(B)2V when compared to the other two nebulizers. NS(B)2V presented a mass percentage with a diameter of 3 mum or less and a sufficient outflow for use in ventilation and pulmonary permeability studies. 4. Comparison of the mass collected in the cascade impactor and the total mass generated by the NS(B), NS(B)1V and NS(B)2V nebulizers showed, on average, 4.5% efficiency in radioacrosol generation with a diameter of less than 16 mum and 3.2% efficiency for a diameter of 3 mum or less. 5. The PITT#1 nebulizer, generating 97% of the total nebulized mass with an MMD of 3 mum or less, showed the lowest outflow among the nebulizers tested (0.011 ml/min).