Rss feed problem with the "guests" names

Hello guys,

In my forum , I let the visitors to post their own topics on a specific category.
What I wanted to do , is to create a custom rss feed to use it my own.
However I see that messages posted by guests , are not displayed in the rss feed by their guest's chosen names , but all of them are appeared as one user , as anonymous.
<dc:creator>Anonymous</dc:creator>
Is there any way , to get in the rss feed the name of the guest of each topic?
Thanks.