Four dimensional cone-beam computed tomography reconstruction using multi-phase projections

Restricted by the hardware, the projection number at a single phase for 4D-CBCT imaging is very low or even less than 10, thus the associated reconstruction by using conventional reconstruction algorithms will be constrained by serious streak artifacts and noises. To address this problem, in this paper, we are aiming to develop an approach to reconstruct the 4D-CBCT image with multi-phase projections, which means that when the images at one phase were estimated not only from the projection data of the current phase but also the projections at the other phases. The proposed approach is based on the assumption that the image at one phase can be viewed as the motion-compensated image of another phase. Specifically, in this work, we formulate a cost function using multi-phase projections to construct the fidelity term and the TV regulation method was adopted. The Gradient-Projection-Barzilai-Linesearch (GPBL) method was used to optimize the complex cost function. Physical phantom and real patient data were used to evaluate the proposed algorithm. Results show that the proposed approach can effectively reduce the noise and artifacts, which suggest that the introduction of additional temporal correlation (along the phase direction) can improve the 4D-CBCT image quality.