Epipolar Consistency Conditions for Motion Correction in Weight-Bearing Imaging

Abstract

Recent C-arm CT systems allow for the examination of a patient’s knees under weight-bearing conditions. The standing patient tends to show involuntary motion, which introduces motion artifacts in the reconstruction. The state-of-the-art motion correction approach uses fiducial markers placed on the patients’ skin to estimate rigid leg motion. Marker placement is tedious, time consuming and associated with patient discomfort. Further, motion on the skin surface does not reflect the internal bone motion. We propose a purely projection based motion estimation method using consistency conditions of X-ray projections. The epipolar consistency between all pairs of projections is optimized over various motion parameters. We validate our approach by simulating motion from a tracking system in forward projections of clinical data. We visually and numerically assess reconstruction image quality and show an improvement in Structural Similarity from 0.912 for the uncorrected case to 0.943 using the proposed method with a 3D translational motion model. Initial experiments showed promising results encouraging further investigation of practical applicability.