Dual-Energy Cone-Beam CT Using Two Orthogonal Projection Views: A Phantom Study

This study proposes a novel imaging and reconstruction framework for dual-energy cone-beam CT (DECBCT) using only two orthogonal X-ray projections at different energy levels (2V-DECBCT). The goal is to enable fast and low-dose DE volumetric imaging with high spectral fidelity and structural accuracy, suitable for DECBCT-guided radiation therapy. We introduce a framework for 2V-DECBCT based on physics-informed dual-domain diffusion models. A cycle-domain training strategy is employed to enforce consistency between projection and volume reconstructions through a differentiable physics-informed module. Furthermore, a spectral-consistency loss is introduced to preserve inter-energy contrast during the generative process. The model is trained and evaluated using 4D XCAT phantom data under realistic anatomical motion. The method produces high-fidelity DECBCT volumes from only two views, accurately preserving anatomical boundaries and suppressing artifacts. Subtraction maps computed from the reconstructed energy volumes show strong visual and numerical agreement with ground truth. This work presents the first diffusion model-based framework for 2V-DECBCT reconstruction, demonstrating accurate structural and spectral recovery from extremely sparse inputs.