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Characterization of 99mTc-DTPA aerosols for lung permeability studies
P Diot1, E Galinier, D Grimbert
1Groupe de Pneumologie, INSERM EMI-U 00-10, INSERM U316, CHU Bretonneau, Tours, France.
Background:
The interpretation of 99mTc diethylenetriamine pentaacetate (99mTc DTPA) aerosol clearance is based on the hypothesis that the 99mTc-DTPA complex is not altered by the nebulization process.
Objectives:
To characterize (1) the radiochemical purity (RCP) of 99mTc-DTPA and the stability of labeling after jet nebulization, and (2) the particle size distribution of the aerosol.
Methods:
RCP and stability--the aerosol was driven by oxygen, captured on filters which were eluted and RCP was checked by thin layer chromatography. Particle size distribution--the aerosol was generated using dry air (50 psi) at three different flow rates, i.e. 3 (1 run), 6 (4 runs) and 9 l x min(-1) (4 runs). The mass median aerodynamic diameter (MMAD) and the geometric standard deviation (sigma(g)) were determined using a cascade impactor from the radioactivity counted on each stage.
Results:
The RCP was more than 95% in all cases. Mean MMAD (+/-SD) was 0.70 microm (+/-0.07) at 9 l x min(-1), 0.93 microm (+/-0.05) at 6 l x min(-1) (p < 0.05) and 1.50 microm at 3 l x min(-1). Mean sigma(g) (+/-SD) was 2.02 (+/-0.08) at 9 l x min(-1), 2.00 (+/-0.16) at 6 l x min(-1) and 1.90 at 3 l x min(-1).
Conclusion:
This study demonstrates (1) that the high RCP of 99mTc-DTPA is not affected by jet nebulization, even when using oxygen at a high flow rate, and (2) that when using a flow rate between 6 and 9 l x min(-1), the MMAD remains optimal for peripheral lung deposition.