A Method for Collision Avoidance in 4π External Beam Radiation Therapy

Abstract

In this study, a method for collision avoidance (CA) in external beam radiation therapy (EBRT) is proposed. The method encompasses the analysis of all positions of the moving components of the beam delivery system, such as the treatment table and gantry, including patient specific information obtained from the computed tomography (CT) images. This method eliminates the need for time-consuming dry runs prior to the actual treatments. This method includes a rigorous computer simulation and CA check prior to each treatment. With this treatment simulation, it is possible to quantify and graphically represent all positions and corresponding trajectories of all points of the moving parts during treatment delivery. The development of the workflow includes several steps: (a) derivation of combined dynamic equation of motion of the EBRT delivery systems, (b) developing the simulation model capable of drawing the motion trajectories of the specific points, (c) developing the interface between the model and the treatment plan parameters, such as couch and gantry parameters for each field. The patient CT images were registered to the treatment couch, so the patient dimensions were included into the simulation. The treatment field parameters were structured in an XML file that was used as an input into the dynamic equations. The trajectories of the moving components were plotted on the same graph using the dynamic equations. If the trajectories intersect, it was the signal that collision exists. This CA method is effective in the simulation of the treatment delivery.