Caml query to search in Sharepoint ListItem MetaInfo

I am working with Sharepoint Lists in Silverlight and I am trying to write a CAML query that returns me all list it开发者_如何学Pythonems (pictures) which where made (effectively taken with the camera) after a specific date.

I found that the ListItems have a MetaInfo property called "vti_ct" which is exactly the date I need. The problem is that I don't know how to write a Caml query on MetaInfo fields!? Because MetaInfo is already a field.

I would be able to write a contains query but that does not help me...

Is it even possible??