Refresh the page duplicates a image uploaded

Hello, all.

I am a new user of CodeIgniter and I am having a problem after uploading a image.
I need to upload a file and everything is fine. After I upload the file I get redirected to a success page. But if I refresh (F5) this page, the image is duplicated in the folder.
As I am renaming it, it never will get the same name, so I can not "override" the image.

I have already tried to "unset($imageUploaded)" after I upload it, but it did not worked.

Anyone has any idea abut how to solve this problem?

Thanks,

Luis.