Technical note: A collision prediction tool using Blender

Non‐coplanar radiotherapy treatment techniques on C‐arm linear accelerators have the potential to reduce dose to organs‐at‐risk in comparison with coplanar treatment techniques. Accurately predicting possible collisions between gantry, table and patient during treatment planning is needed to ensure patient safety. We offer a freely available collision prediction tool using Blender, a free and open‐source 3D computer graphics software toolset. A geometric model of a C‐arm linear accelerator including a library of patient models is created inside Blender. Based on the model, collision predictions can be used both to calculate collision‐free zones and to check treatment plans for collisions. The tool is validated for two setups, once with and once without a full body phantom with the same table position. For this, each gantry‐table angle combination with a 2° resolution is manually checked for collision interlocks at a TrueBeam system and compared to simulated collision predictions. For the collision check of a treatment plan, the tool outputs the minimal distance between the gantry, table and patient model and a video of the movement of the gantry and table, which is demonstrated for one use case. A graphical user interface allows user‐friendly input of the table and patient specification for the collision prediction tool. The validation resulted in a true positive rate of 100%, which is the rate between the number of correctly predicted collision gantry‐table combinations and the number of all measured collision gantry‐table combinations, and a true negative rate of 89%, which is the ratio between the number of correctly predicted collision‐free combinations and the number of all measured collision‐free combinations. A collision prediction tool is successfully created and able to produce maps of collision‐free zones and to test treatment plans for collisions including visualisation of the gantry and table movement.