Motion tracking in narrow spaces: A structured light approach

We present a novel tracking system for patient head motion inside 3D medical scanners. Currently, the system is targeted at the Siemens High Resolution Research Tomograph (HRRT) PET scanner. Partial face surfaces are reconstructed using a miniaturized structured light system. The reconstructed 3D point clouds are matched to a reference surface using a robust iterative closest point algorithm. A main challenge is the narrow geometry requiring a compact structured light system and an oblique angle of observation. The system is validated using a mannequin head mounted on a rotary stage. We compare the system to a standard optical motion tracker based on a rigid trackingtool. Our system achieves an angular RMSE of 0.11 degrees demonstrating itsrelevance for motion compensated 3D scan image reconstructions as wellas its competitiveness against the standard optical system with an RMSEof 0.08 degrees. Finally, we demonstrate qualitative result on real face motionestimation.