A Feldkamp-Type Approach to Limited-Angle On-Board Three-Dimensional Imaging for External Beam Radiotherapy Target Localization

Accurate three-dimensional tumor localization in radiotherapy is critical to the treatment outcome, particularly when high dose gradients are present. Digital tomosynthesis (DTS) is a method to reconstruct three-dimensional (3D) images from two-dimensional (2D) x-ray projections acquired over limited scan angles. In this study, we have used a Feldkamp-type approach to reconstruct DTS images. The accuracy of the reconstruction was evaluated by computing the pixel signal-to-noise ratio (PSNR) and the mutual information (MI) shared between DTS images and 3D cone-beam computed tomography (CBCT) images. The results indicate the DTS slices appeared similar to coincident CBCT planes and yielded substantially more anatomic information than conventional kilovoltage (kV) verification radiographs, but required a lower imaging dose, faster acquisition, and more geometric flexibility than CBCT.