A Multi-site Microdosimeter for Clinical Beam Characterization

Anna Bianchi ^* Anna Selva Massimo Rossignoli Valeria Conte

• Legnaro National Laboratories (INFN), Legnaro, Italy

Different types of radiation cause varying levels of biological damage, even when the physical dose is the same, due to the unique way energy is distributed at the subcellular level. The MUSICA project is focused on creating an innovative detector that not only provides quantitative dosimetric data but also qualitative insights. These qualitative insights are derived from measuring physical parameters that are linked to biological effectiveness. This approach, particularly in proton therapy, aims to enhance treatment precision and improve clinical outcomes.Radiation damage occurs through processes at multiple scales, from the DNA level (2 nm) to the entire cell nucleus (10 μm). The stochastic spatial distribution of energy deposition can be studied using microdosimetric techniques with tissue-equivalent gas proportional counters (TEPC). While many studies employing TEPCs have examined sites smaller than 2 μm (such as chromosomes), characterization at the 10 μm scale has typically been performed useing solid-state detectors. However, gas microdosimeters provide benefits in terms of sensitivity, geometry, and tissue equivalence, making it highly advantageous to conduct multi-site characterization using a single detector.The project has developed a TEPC with two charge collection zones, allowing for the definition of two different volume sizes (e.g., 1 and 10 μm) without changing the gas pressure. This will enable dualdimension microdosimetric characterization in a single measurement session without switching detectors. The resulting bi-dimensional data will be integrated into new radiobiological models that link physical measurements to biological outcomes, enhancing our understanding of how ionizing radiation affects living tissue.