Reconstruction of 4D deformed CT for moving anatomy

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.