Robustness study of patient-specific range modulators for conformal FLASH proton therapy

Cancer is a leading cause of death worldwide and various treatment options are available to combat this disease. One commonly used approach is external radiation therapy, which aims to destroy cancer cells by damaging their DNA through radiation delivery. Proton therapy (PT), an advanced technique, offers the potential for improved precision in targeting the tumor volume compared to conventional radiotherapy methods. Recently, it has been shown that using ultra-high dose rates would less damage the healthy tissues while maintaining the same tumor control. The characteristic of this new method, also known as FLASH, is to deliver the prescribed dose in a much shorter time window. In order to administer the dose within a limited time frame, an additional component must be incorporated. This component is a 3D patient-specific range modulator that passively degrades proton beam energy in order to perfectly match the tumor shape. The addition of a new component can create uncertainties due to various factors. In this master’s thesis, we will study the impact of 3 types of uncertainties on dose delivery in FLASH-PT: spot size uncertainties, spot position uncertainties, and analysis of air inclusions when printing the patient-specific range modulator. To achieve this goal, we computed simulations of beam delivery in OpenTPS (an open-source treatment planning system developed at UCLouvain). Following the analysis of the results, we observe that some characteristics, particularly the spot size, are more important to be heeded of but the field still seems to be promising. However, this study did not cover all the uncertainties that could appear. Further studies still need to be made in order to validate this technique.