Graphics, Figures & Tables ⇒ Set picture transparency on white color

[m.carrara3]

Here's my problem:
I'm making a presentation using Beamer and I want the logo of my university on the background as a background image. Easily done.
Now, in the presentation i need to include some pictures via \includegraphics command and herre's the thing:
How can I set the white background color of my pictures to be transparent so the background of the frame is clearly visible? Is it possible?

Thanks a lot to anyone who will answer.

Matteo