Reconstruction of 4D deformed CT for moving anatomy

Abstract: Purpose: To develop a 4DCT reconstruction technique that improves time resolution when the anatomy moves with respiration. Method: A cone-beam CT (CBCT) scan is performed and a breathing signal is acquired. At the same time a set of simulated CBCT projections is created from a prior source CT deformed by a time-dependent parametric deformation model. The model parameters are iteratively adjusted until the simulated projections optimally resemble the acquired images. This concept was tested with three different simulated deformation scenarios approximating a moving lung tumor with rigid and elastic deformation and a 3D anatomical expansion/contraction. Results: The known deformation was accurately reconstructed in all three scenarios. The method is reasonably robust to noise and contrast mismatch in the projections Conclusion: Matching simulated to actual CBCT projections can adequately constrain a 4D model of breathing-induced motion that occurs during acquisition of the CBCT data.