Reducing secondary cancer risk by measuring neutron exposure in light ion beam radiotherapy

• Applicant: Dr. José Vedelago
• Subject Area: Medical Physics, Biomedical Technology ; Nuclear Medicine, Radiotherapy, Radiobiology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 495217943

Cancer treatment with light ion beams allows maximizing the effect on the tumour while minimising the risk in healthy tissues. Inevitably, when ion beams are used for cancer treatment, secondary neutrons are produced in nuclear reactions, mainly inside the patient’s body. Those neutrons can reach healthy tissues located far away from the treatment volume. Thus, secondary neutrons present a risk for long-term effects and secondary cancers; hence, precise knowledge of dose deposition due to secondary neutrons is required. Furthermore, these neutrons can reach high energies, up to the point that it is not possible to use current dosimetry techniques.The goal of this project is to establish a procedure to measure secondary neutron dose. For this, Fluorescent Nuclear Track Detectors (FNTDs) are among the most promising detector technologies. FNTD technology is nowadays being adapted at the German Cancer Research Center (DKFZ; Heidelberg, Germany). To cover the gap of high-energy neutrons, computational simulations followed by experimental calibrations with quasi-monoenergetic neutron sources will be used to optimize the FNTD methodology. Although limited when dealing with high-energy neutrons, other dosimetry methods like thermoluminescent and polymer-based detectors will be used for comparison purposes. As one of the deliverables of the project, the method for high-energy neutron dosimetry using FNTDs will be established, and experimental measurements will be carried out at the Heidelberg Ion-Beam Therapy Center (HIT; Heidelberg, Germany). The experimental results will be further used as input for the validation and optimization of radiation transport simulation codes. With this, secondary neutron dose information can be included in clinical treatment planning systems, with the aim of predicting the long-term risk of secondary cancer induction. This will assist clinicians when choosing the best treatment plan for each patient, especially in cases when pregnant women or paediatric patients are treated, for which long-term risk is an important factor. Finally, this project will contribute to reduce the currently existing large uncertainties concerning neutron dose in clinical applications.

• DFG Programme: Research Grants