Last modification: 25/05/2022 Authors: Iñigo González Lizarraga, Alejandro Barranco López, Sheila Calvo Carrillo, Mónica Hernández Hernández All of them work together in Hospital Clínico Lozano Blesa de Zaragoza, Spain. _________________________________________________________________________________________________________________________________________________________________________________ SCRIPT FOR COLLISION DETECTION IN EXTERNAL RADIOTHERAPY PLANNING This script detects collisions between the gantry of a LINAC and the couch or the patient during the planning phase. The software is implemented in C# programming language, being able to work with Eclipse TPS, from Varian Medical Systems. The script must be executed in the planning phase. It reads the RT.Structures and the loaded RT.Plan from the TPS. It creates as surface the countour of the collimator path for each beam on the plan. Then it checks the distance between all collimator path points and the couch and patient surfaces. If whatever of this calculated distances is lower than a defined tolerance, the script shows a warning window and a 3D representation of the geometry. Before using it, it is important to adapt some parameters to our LINAC: - Radius of collimator - Clearence (distance from isocenter to collimator surface) - Distance tolerance (we can estimate it by doing a machine test) - Exporting folder path. (to obtain a 3D representation of the situation) Machine Test to determinate distance tolerance (recommended 25 mm if spacing is equal to 10 mm): - Step 1. Put the couch in a reasonable treatment position - Step 2. For the following couch angles (15,20,25,30,45), rotate de gantry until it collides with the couch. Note this critical gantry angles. - Step 3. In Eclipse, for the same couch angles, execute the script at different gantry angles and find this critical gantry angle. Repeat this for different distance tolerances. - Step 4. Determinate which distance tolerance matches better the reference results from the second step.