%0 Generic
%A Hahn, Andreas
%D 2019
%F heidok:26901
%R 10.11588/heidok.00026901
%T Moving Metal Artifact Reduction and Intrinsic Gating for Cone-Beam CT Scans of the Thorax Region
%U https://archiv.ub.uni-heidelberg.de/volltextserver/26901/
%X In this work, novel algorithms in the field of retrospective intrinsic respiratory and cardiac gating and moving metal artifact reduction (MMAR) for cone-beam CT (CBCT) scans that are used in image-guided radiation therapy (IGRT) were developed. The added difficulty for CBCT scans is the relatively long acquisition time of up to 60 s compared to 0.25 s for clinical CT scans. The occuring respiratory and cardiac motion in combination with metal inserts cannot be handled with classical metal artifact reduction (MAR) methods. The proposed MMAR algorithms utilize an approach that combines the fields of motion compensation (MoCo) with classical MAR methods. In  order for the MMAR methods to work, the motion state has to be known for every projection angle. A novel intrinsic gating approach, that automatically generates a list  of potential motion surrogate candidates and identifies the best, was developed and used as a basis for the MMAR algorithms, so they can be applied for patients where  no externally recorded motion signal is available. Whereas classical approaches for intrinsic gating are not designed for a laterally shifted detector, that is commonly used  in IGRT with a CBCT, the novel algorithm works on scans with or without a shifted detector. It can also be used as a basis for 4D (3D + respiratory) or 5D (3D + respiratory  + cardiac) MoCo algorithms.