Status: open-source
RTK is an open-source and cross-platform software for fast circular cone-beam CT reconstruction based on the Insight Toolkit (ITK). RTK is developped by the RTK consortium. Find out more on OpenRTK website. 
Features- Basic operators for reconstruction: filtering, forward and backward projections
 - Multithreaded CPU and GPU versions
 - Tools for respiratory motion correction
 - I/O for several scanners
 - Preprocessing of raw data for scatter correction