[vtkusers] reslicing through 2 added volume (with alpha values) in a renderer

[Flo]

Dear all,

Is it possible to actually reslice from 2 added volume in a renderer ?
My end goal is to add/match an image actor to a vtkImagePlaneWidget  
to display a segmented region of interest.

OR, how should I do to add a texture to the resliced output of a  
vtkImagePlaneWidget and update it with respect to an external volume  
(the segmented one) ?

I'll be grateful for any idea and suggestions are mine so far are not  
satisfactory.

Regards,

Flo.