Radiation effect models
The relative biological effectiveness (RBE) is a quantification of the higher effect of ion radiation compared to reference photon radiation. Models for RBE are frequently used in treatment planning of heavy ion radiotherapy as well as radiation protection and radiobiology. Patient safety as well as assessment of consequences from radiation exposure necessitates accurate model predictions. Therefore, we work on the development of effect models and the systematic comparison of RBE models on the basis of in-vitro experiments, in-vivo preclinical data and clinical results.
![Principle of the local effect model (LEM). The effect of high local doses around ion trajectories is related to the effect of photon irradiation with the same dose.](/fileadmin/_processed_/1/1/csm_RBE_models_html_5f7a869c_ce458c6456.gif)
The local effect model (LEM) is a model for RBE quantification forf multiple endpoints. It was developed in our group by M. Scholz in the context of the GSI pilot project of carbon ion therapy for skull base tumor patients. It is still used in carbon irradiation therapy planning at several centers, and has been improved and validated in several steps up to LEM IV, which is our current standard.
![Features of the GSI RBE model comparison infrastructure. Fixed underlying particle transport calculations and treatment planning system eliminates non-model based differences. The standardised evaluation procedure allows for comparability btw. the models.](/fileadmin/_processed_/1/e/csm_RBE_models_html_1b4a4305_3403cd0e9a.gif)
Besides the LEM, there are various other RBE models. They are based on different principles and agree or disagree in specific contexts. Their concepts and performance can give insights in their validity. We established a dedicated platform for RBE model comparison, which allows evaluation of the uncertainty arising due to RBE model selection. It is based on the GSI in-house treatment planning system TRiP (treatment planning for particles) and statistical measures for comparative analysis.
Selected publications
Herr L, Friedrich T, Durante M, Scholz M. Investigation of the Impact of Temporal Dose Delivery Patterns of Ion Irradiation with the Local Effect Model. Radiation Research 201:275-286 (2024). doi:10.1667/rade-23-00074.1
Pfuhl T, Friedrich T, Scholz M. Comprehensive comparison of local effect model IV predictions with the particle irradiation data ensemble. Medical Physics 49:714-726 (2021). doi:10.1002/mp.15343
Hufnagl A, Johansson G, Siegbahn A, Durante M, Friedrich T, Scholz M. Modeling secondary cancer risk ratios for proton versus carbon ion beam therapy: A comparative study based on the local effect model. Medical Physics 49:5589-5603 (2022). doi:10.1002/mp.15805
Grün R, Friedrich T, Traneus E, Scholz M. Is the dose‐averaged LET a reliable predictor for the relative biological effectiveness? Medical Physics 46:1064-1074 (2019). doi:10.1002/mp.13347
Friedrich T, Ilicic K, Greubel C, et al. DNA damage interactions on both nanometer and micrometer scale determine overall cellular damage. Scientific Reports 8:16063 (2018). doi:10.1038/s41598-018-34323-9
Steinsträter O, Grün R, Scholz U, Friedrich T, Durante M, Scholz M. Mapping of RBE-Weighted Doses Between HIMAC– and LEM–Based Treatment Planning Systems for Carbon Ion Therapy. International Journal of Radiation Oncology*Biology*Physics 84:854-860 (2012). doi:10.1016/j.ijrobp.2012.01.038
Scholz M, Kellerer AM, Kraft-Weyrather W, Kraft G. Computation of cell survival in heavy ion beams for therapy. The model and its approximation. Radiation and Environmental Biophysics 36:59-66 (1997). doi:10.1007/s004110050055