Software to register a 2D image to a 3D volume
The software Amira from Visage Imaging has some excellent built-in registration features. I never tried that exact problem, though.

It is unfortunately pretty pricy, but you can download a free trial version of it from the website to give it a try. http://www.vsg3d.com/amira/overview

I also found some well implemented registration algorithms in the software MedInria, an open source and free software specially developed for medical image analysis. http://med.inria.fr