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 ven tilation (V) imaging agent compatible with clinical applications. This stud y aimed at defining the value of an inhaled radioactive aerosol (Tc-99m-DTP A) and a 'pseudogas' (Technegas) in the assessment of regional ii in health y conscious calves by comparing Tc-99m-DTPA and Technegas deposition (D) im ages 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-D TPA or Technegas and Kr-81m distributions. Results of this analysis showed that the Tc-99m-DTPA aerosol droplets were unable to reach the lung parench yma because of significant particle impaction in the major conducting airwa ys. Better definition of the ventilated lung was obtained when using Techne gas because of minimal deposition in conducting airways. Furthermore, the T echnegas and Kr-81m distribution patterns were highly equivalent. (C) 2000 Harcourt Publishers Ltd.