Can't find it at the moment, but someone did in fact create a passable homebrew CT scanner based on a small Faxitron medical-specimen X-ray machine of the sort that can be commonly found on eBay.

Edit: found it ( http://www.rtftechnologies.org/physics/faxitron-DX50-CT-scan... )

These machines are good for up to 8-10 layers of 1-oz copper.