Comparison between radioactive aerosol, Technegas and krypton for ventilation imaging in healthy calves

The use of lung scintigraphy in calves necessitates the validation of a ventilation (V) imaging agent compatible with clinical applications. This study aimed at defining the value of an inhaled radioactive aerosol (Tc-99m-DTPA) and a 'pseudogas' (Technegas) in the assessment of regional ii in healthy conscious calves by comparing Tc-99m-DTPA and Technegas deposition (D) images to (V)over dot (V) images obtained from the steady-state inhalation of the short half-life krypton 81 (Kr-81m) gas. Images were compared by analysis of radioactivity distribution in computer-generated regions of interest within the right lung and D to V ratio images were generated in order to highlight areas of mismatching between Tc-99m-DTPA or Technegas and Kr-81m distributions. Results of this analysis showed that the Tc-99m-DTPA aerosol droplets were unable to reach the lung parenchyma because of significant particle impaction in the major conducting airways. Better definition of the ventilated lung was obtained when using Technegas because of minimal deposition in conducting airways. Furthermore, the Technegas and Kr-81m distribution patterns were highly equivalent. (C) 2000 Harcourt Publishers Ltd.