Patient alignment estimation in six degrees of freedom using a CT-scan and a single x-ray image

Particle beam treatment allows accurate dose delivery onto carcinogen tissue. The reachable accuracy is limited by patient alignment errors relative to the beam source. Errors can be corrected manually or by automatic comparison of two X-ray images to a CT-scan but correction mostly does not cover all degrees of freedom (DoF). In this contribution we present a solution that makes use of one X-ray image and computes full 6 DoF alignment correction by gray value based comparison to a CT. By using regions of interest, we are able to increase performance and reliability.