Image management

I found out that when I remove a picture out of a post, the picture is still in de wp-content/uploads map.
When I add the same picture again (elsewhere in the post) it creates the same image name but adding a number to it.

What I’m worried about is, that in time the Upload is full of pictures that are not used anymore, or are a copy of another.
Is there a way to know which images are actually linked and used?