Projection Matrix Based Iterative Reconstruction Algorithm for Robotic CT

Abstract

Robotic computed tomography (CT) consists of two separate manipulators which carry the source and detector, respectively. Various errors occur in motion due to lack of rigid connection, which may change scanning trajectory of this system. Some methods aimed at recovering geometry relation have occurred. However, these methods are relied on circular scanning trajectory. Projection matrix is the matrix form of geometry definition, which contains geometric parameters in the matrix and transforms geometry calculation into homogeneous matrix calculation. It is suitable for robotic CT because of its irrelevance between angles. Besides, iteration reconstruction algorithm makes no assumptions on scanning trajectories, which is suitable for arbitrary scanning trajectories. Hence, this study combines iteration reconstruction algorithm with the concept of projection matrix to fill the gap. In this study, we established a transformation between projection matrix and ray function, and construct corresponding projection model. Projection matrix based iterative reconstruction algorithm was then developed and validated by simulation and experiment. Uncooperative rotation of manipulators, jitter in motion and non-circular motion trajectories were simulated. FDK, projection matrix-based FDK and projection matrix-based iterative method were compared. Real experiments were also conducted. The results showed projection matrix based iterative reconstruction could lead to better image quality against motion error. In summary, this study provided a high-precision reconstruction approach for robotic CT.

Keywords

• Robotic CT
• calibration phantom
• projection matrix