CT-to-Cone-beam CT deformable registration

ONLINE ADAPTIVE RADIATION THERAPY (ART) allows real-time treatment adaptations based on the current patient anatomy and geometry. In a typical online ART process, a computed tomography (CT) image is usually acquired prior to the treatment course for treatment planning purposes. Before each treatment fraction, a cone-beam CT (CBCT) image is then obtained, on which the treatment plan is redesigned to account for setup errors, deformations of tumor and other organs, and the change of their relative locations. Deformable image registration (DIR) technique plays an important role in this process in establishing a correspondence between voxels in the CT and the CBCT for various purposes, for instance, transferring the organ contours from the planning CT images to the daily CBCT images. It is, hence, desirable to have an accurate and robust DIR algorithm to facilitate this step.