Development of a treatment planning system for superficial x-ray radiotherapy using Monte Carlo database

<i>Objective</i>. Currently, superficial x-ray radiotherapy does not take advantage of modern treatment planning technologies. To address the problem, a treatment planning system for superficial x-ray radiotherapy has been developed using a database generated through Monte Carlo simulations. The system, called SXRTDose, can be used to optimize irradiation strategies by adjusting energy, filtration, and applicator aiming to deliver a planned dose to the target volume while minimizing radiation risk to surrounding normal tissues.<i>Approach</i>. TOPAS Monte Carlo code was used for establishing the dosimetric database by modeling parameters of a commercial superficial x-ray radiotherapy device and by calculating depth-dose information in a water phantom. After the radiation physics aspects have been verified, detailed Monte Carlo simulations of absorbed doses under different irradiation parameters including five skin models (representing location of the abdomen, cheek, forehead, limbs, and nose), three x-ray energies (50 kV, 70 kV, and 100 kV), corresponding filters and applicators were performed resulting in a comprehensive database. A python-based graphical user interface was developed to support the clinical application of the treatment planning system for superficial x-ray radiotherapy.<i>Results</i>. Compared to experimental results reported in the literature, the relative errors from water phantom simulations for the superficial x-ray radiotherapy system is acceptable. The developed treatment planning system utilizes dose-volume histograms to quantitatively evaluate the clinical applicability of various irradiation plans for skin cancer treatment. The application of the software is found to provide rapid and accurate dose guidance to clinical users in selecting optimal and alternative equipment parameters.<i>Conclusion</i>. The potential and feasibility of a treatment planning system for superficial x-ray radiotherapy have been evaluated, demonstrating its capability to deliver rapid, accurate, and concise dosimetry references. This enhances therapeutic guidance and treatment effectiveness, while addressing the present challenge of inadequate dosimetry support in the field of superficial radiotherapy.