Unmarked External Breathing Motion Tracking Based on B-spline Elastic Registration

In robotic radiosurgery, tracking and modeling of breathing motion is crucial for accurate treatment planning while dealing with tumor inside the thoracic or abdominal cavity, because patient respiration can induce considerable external and internal motion in the thoracic and abdominal regions. Currently, methods for characterizing respiration motion mainly focused on sparse point markers placed on the surface of chest. However, limited number of markers failed to encode the comprehensive features of respiratory motion. Besides, the markers can make partial occlusion during the operation. In this work, a novel method for respiratory motion characterization based on RGB-D camera and B-spline elastic registration is proposed. Images taken from depth camera are used for modeling of abdomen surface during respiration, while B-spline elastic registration technique is applied to restrain the measuring area into an anatomically consistent region during the treatment. In addition, an elastic dynamic motion simulator is designed to test our proposed method. Finally, the feasibility of the method and the device is verified by error analysis and shape comparison.