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.
© 2008 Optical Society of America
Original Manuscript: April 23, 2007
Revised Manuscript: July 29, 2008
Manuscript Accepted: September 14, 2008
Published: November 5, 2008
Vol. 4, Iss. 1 Virtual Journal for Biomedical Optics
Zikuan Chen, Vince D. Calhoun, and Shengjiang Chang, "Compensating the intensity fall-off effect in cone-beam tomography by an empirical weight formula," Appl. Opt. 47, 6033-6039 (2008)