Here's a good idea of what to expect for the test ...
http://www.vascularweb.org/patients/NorthPoint/
CT_Scan.html
Here's an example of the result of CT angiography ...
http://www.ct-angiogram.com/
The pictures near the bottom of the page show a CT angiogram compared with a more traditional angiogram.
You've probably seen a typical CT machine on television, but in case you haven't here's a site with a couple pictures ...
http://www.radiologyinfo.org/en/info.cfm?PG=angioct 
