  We present for the first time a general 6DoF trajectory planning method that
can be used in real-time image guided radiation therapy procedures for robotic
stabilization of dynamically moving tumor targets. As the radiation beam is
always on during the motion compensation process, it is mandatory that the 6D
correction trajectory is optimal both spatially and temporally in order to
maximize radiation to the tumor and minimize unintentional irradiation of
healthy tissues. Unlike prior works, which relied on motion control approaches
as PID or other controllers, this work presents the concept of motion planning,
where all potential 6D trajectories are searched using ultrafast optimization
methods and the best trajectory is chosen. As the method formulates the problem
as an objective function to be solved, it allows high flexibility in that users
can optimize various performance requirements such as mechanical robot limits,
patient velocities, or other aspects that must operate within certain limits in
order to ensure a safe medical process.
