title: Compensating the intensity fall-off effect in cone-beam tomography by an empirical weight formula.
abstract: The Feldkamp-David-Kress (FDK) algorithm is widely adopted for cone-beam reconstruction due to its one-dimensional filtered backprojection structure and parallel implementation. In a reconstruction volume, the conspicuous cone-beam artifact manifests as intensity fall-off along the longitudinal direction (the gantry rotation axis). This effect is inherent to circular cone-beam tomography due to the fact that a cone-beam dataset acquired from circular scanning fails to meet the data sufficiency condition for volume reconstruction. Upon observations of the intensity fall-off phenomenon associated with the FDK reconstruction of a ball phantom, we propose an empirical weight formula to compensate for the fall-off degradation. Specifically, a reciprocal cosine can be used to compensate the voxel values along longitudinal direction during three-dimensional backprojection reconstruction, in particular for boosting the values of voxels at positions with large cone angles. The intensity degradation within the z plane, albeit insignificant, can also be compensated by using the same weight formula through a parameter for radial distance dependence. Computer simulations and phantom experiments are presented to demonstrate the compensation effectiveness of the fall-off effect inherent in circular cone-beam tomography.
authors.affiliation: The Mind Research Network, Albuquerque, New Mexico 87131, USA. zchen@mrn.org
authors.forename: Zikuan
authors.initials: Z
authors.lastname: Chen
authors.forename: Vince D
authors.initials: VD
authors.lastname: Calhoun
authors.forename: Shengjiang
authors.initials: S
authors.lastname: Chang
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D004867:Equipment Design; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D015233:Models, Statistical; D055095:Optics and Photonics; D010363:Pattern Recognition, Automated; D019047:Phantoms, Imaging; D012542:Scattering, Radiation; D014965:X-Rays