[vtkusers] Problems with decimation

[mam06bhv]

Hello community,

I want to decimate a 3D model of a head. For this I use vtkdDecimatePro. 
The decimation is working finde but I want to know how much objects 
(e.g. triangles) the algorithm has decimate. For this I use the 
getNumberofCells function. My problem is when I load the Image I 
calculate the number of Cells. After the decimation I get the same 
number of cells but this can't be right, or? So could someone tell me 
how I can get the correct number?
Thanks