Joint CT/CBCT deformable registration and CBCT enhancement for cancer radiotherapy

[Display omitted] ► We propose an algorithm to simultaneously perform CT–CBCT registration and image enhancement of CBCT. ► We combine the Mutual Information (MI) similarity measure with the Sum of Squared Differences (SSD) error measure to an energy term that is minimized iteratively. ► Incorporating an intensity correction term improves the registration results. ► Our algorithm is validated on synthetic Ground-Truth data and six clinical datasets. This paper details an algorithm to simultaneously perform registration of computed tomography (CT) and cone-beam computed (CBCT) images, and image enhancement of CBCT. The algorithm employs a viscous fluid model which naturally incorporates two components: a similarity measure for registration and an intensity correction term for image enhancement. Incorporating an intensity correction term improves the registration results. Furthermore, applying the image enhancement term to CBCT imagery leads to an intensity corrected CBCT with better image quality. To achieve minimal processing time, the algorithm is implemented on a graphic processing unit (GPU) platform. The advantage of the simultaneous optimization strategy is quantitatively validated and discussed using a synthetic example. The effectiveness of the proposed algorithm is then illustrated using six patient datasets, three head-and-neck datasets and three prostate datasets.