Redundancies in X-ray images due to the epipolar geometry for transmission imaging

In Computer Vision, the term epipolar geometry describes the intrinsic geometry between two pinhole cameras. While the same model applies to X-ray source and detector, the imaging process itself is very different from visible light. This paper illustrates the epipolar geometry for transmission imaging and makes the connection to Grangeat’s theorem, establishing constraints on redundant projection data along corresponding epipolar lines. Using these redundancies, a geometric consistency metric is derived. Our metric could be applied to any pair of transmission images and could be used for pose refinement, calibration correction and rigid motion estimation in fluoroscopy and flat detector computed tomography (FD-CT) . In addition to the theoretical contribution, this paper investigates the properties and behavior of the metric for the purpose of re-calibration of an FD-CT short scan for narrow angular range.