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BioMed Research International
Volume 2016 (2016), Article ID 4382854, 19 pages
Research Article

3D-2D Deformable Image Registration Using Feature-Based Nonuniform Meshes

1University of Texas at Dallas, Richardson, TX 75080, USA
2University of Texas Southwestern Medical Center, Dallas, TX 75235, USA
3University of New Mexico, Albuquerque, NM 87131, USA

Received 11 September 2015; Accepted 28 December 2015

Academic Editor: Cristiana Corsi

Copyright © 2016 Zichun Zhong et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


By using prior information of planning CT images and feature-based nonuniform meshes, this paper demonstrates that volumetric images can be efficiently registered with a very small portion of 2D projection images of a Cone-Beam Computed Tomography (CBCT) scan. After a density field is computed based on the extracted feature edges from planning CT images, nonuniform tetrahedral meshes will be automatically generated to better characterize the image features according to the density field; that is, finer meshes are generated for features. The displacement vector fields (DVFs) are specified at the mesh vertices to drive the deformation of original CT images. Digitally reconstructed radiographs (DRRs) of the deformed anatomy are generated and compared with corresponding 2D projections. DVFs are optimized to minimize the objective function including differences between DRRs and projections and the regularity. To further accelerate the above 3D-2D registration, a procedure to obtain good initial deformations by deforming the volume surface to match 2D body boundary on projections has been developed. This complete method is evaluated quantitatively by using several digital phantoms and data from head and neck cancer patients. The feature-based nonuniform meshing method leads to better results than either uniform orthogonal grid or uniform tetrahedral meshes.