title: Respiratory motion estimation from slowly rotating x-ray projections: theory and simulation.
abstract: Understanding the movement of tumors caused by respiratory motion is very important for conformal radiatherapy. However, respiratory motion is very difficult to study by conventional x-ray CT imaging since object motion causes inconsistent projection views, leading to artifacts in reconstructed images. We propose to estimate the parameters of a nonrigid, free breathing motion model from a set of projection views of the thorax that are acquired using a slowly rotating cone-beam CT scanner. This approach involves deforming a motion-free reference thorax volume according to the estimated parameters and comparing its projections to the corresponding measured projection views. The parameters are optimized by minimizing a regularized squared error cost function. Simulation results with a fan-beam geometry show good agreement between the estimated motion and the true motion, which supports the potential of this approach for estimating four-dimensional (three-dimensional spatial + temporal) respiratory motion.
authors.affiliation: Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109-2122, USA. rzeng@eecs.umich.edu
authors.forename: Rongping
authors.initials: R
authors.lastname: Zeng
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Fessler
authors.forename: James M
authors.initials: JM
authors.lastname: Balter
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D006801:Humans; D007091:Image Processing, Computer-Assisted; D015233:Models, Statistical; D008962:Models, Theoretical; D009038:Motion; D009068:Movement; D020266:Radiotherapy, Conformal / Q000379:methods*; D012119:Respiration; D014057:Tomography, X-Ray Computed; D014965:X-Rays