Until recently, x-ray microbeam radiation therapy and x-ray FLASH therapy have only been possible at large synchrotrons, which are huge research facilities. We developed in our team compact alternatives and hence enable preclinical research independent of synchrotrons. We want to go further:

One of my primary objectives for the next five years is the set-up of the first clinically applicable microbeam radiation source based on line-focus X-ray tube technology. This technology enables x-ray beams from micrometre sized emitters (i.e. spatially coherent x-rays) with doses of several 10 probably up to 150 Gy/s. 

This ambitious deep-tech project brakes current x-ray tube records by orders of magnitude and involves innovative tools in electron acceleration and focusing in collaboration with the University of Mainz, enhancing the structure and material combinations in the X-ray target in partnership with the Research Centre Jülich, and establishing a modular pulsed high-voltage source in cooperation with the Hochschule München. 

Recent publications: 

• Petrich, C., Winter, J., Dimroth, A., Wilkens, J. J., & Bartzsch, S. (2025). The compact line-focus X-ray tube for microbeam radiation therapy—Focal spot characterisation and collimator design. Physica Medica, 129, 104861.
• Ahmed, M., Beyreuther, E., Gantz, S., Horst, F., Meyer, J., Pawelke, J., ... & Bartzsch, S. (2024). Design and dosimetric characterization of a transportable proton minibeam collimation system. Frontiers in Oncology, 14, 1473625.
• Bartzsch, S. H., Corde, S., Crosbie, J. C., Day, L. R. J., Donzelli, M., Krisch, M., Lerch, M., Pellicioli, P., Smyth, L. M. L. & Tehei, M. (2020). Technical advances in X-ray microbeam radiation therapy. Physics in Medicine & Biology.
• Bartzsch, S. and Oelfke, U., 2017. Line focus x-ray tubes—a new concept to produce high brilliance x-rays. Physics in Medicine & Biology, 62(22), p.8600.

Understanding the underlying mechanisms of FLASH therapy and spatially fractionated radiation therapy is crucial to optimizing treatment efficacy. To this end, we are investigating the role of radiochemical interactions involving reactive oxygen species (ROS), examining the influence of radiochemical levels in cells and tissues on biological response, and analysing the impact of high-dose rates, radiation doses, and spatial fractionation on cell metabolism and intercellular signalling such as bystander effects. We employ various assays to detect ROS experimentally, for example by employing spin traps and electron spin resonance measurements.

Radiochemistry plays a major role between a few nanoseconds up to around 1 second after radiation absorption. There is growing evidence that this phase is crucial for an understanding of radiation therapy at high dose rates and spatial fractionation. Apart from experimental measurements of radiochemical species, we develop models of the evolution of reactive radiochemical species.

Recent publications:

• Baikalov, A., Abolfath, R., Schüler, E., Mohan, R., Wilkens, J. J., & Bartzsch, S. (2023). Intertrack interaction at ultra-high dose rates and its role in the FLASH effect. Frontiers in Physics, 11, 1215422.
• Abolfath, R., Baikalov, A., Fraile, A., Bartzsch, S., Schüler, E., & Mohan, R. (2023). A stochastic reaction–diffusion modeling investigation of FLASH ultra-high dose rate response in different tissues. Frontiers in Physics, 11, 1060910.
• Abolfath, R., A. Baikalov, S. Bartzsch, N. Afshordi and R. Mohan (2022). "The effect of non-ionizing excitations on the diffusion of ion species and inter-track correlations in FLASH ultra-high dose rate radiotherapy." Physics in Medicine and Biology 67(10).

The success of radiation treatment depends strongly on the tissue and tumour microenvironment – intracellular signalling, immune system, vasculature and oxidative stress. We aim to understand novel treatment strategies, such as FLASH and microbeams better by performing preclinical in vitro and in vivo studies. With various cutting-edge imaging techniques we decipher the secrets of radiation action in cells and tissue.

Focus of our investigations are radio-immune interactions in microbeam and minibeam radiation therapy, bystander signalling and oxidative stress and the role of vascular damage for the efficacy of microbeam radiation therapy.  

Publications:

• Subramanian, N., Čolić, A., Santiago Franco, M., Stolz, J., Ahmed, M., Bicher, S., ... & Schmid, T. E. (2025). Superior Anti-Tumor Response After Microbeam and Minibeam Radiation Therapy in a Lung Cancer Mouse Model. Cancers, 17(1), 114.
• Stolz, J., Rogal, K., Bicher, S., Winter, J., Ahmed, M., Raulefs, S., ... & Schmid, T. E. (2025). The Combination of Temporal and Spatial Dose Fractionation in Microbeam Radiation Therapy. Biomedicines, 13(3), 678.
• Ahmed, M., Bicher, S., Combs, S. E., Lindner, R., Raulefs, S., Schmid, T. E., ... & Bartzsch, S. (2024). In vivo microbeam radiation therapy at a conventional small animal irradiator. Cancers, 16(3).
• Steel, H., Brüningk, S. C., Box, C., Oelfke, U., & Bartzsch, S. H. (2021). Quantification of Differential Response of Tumour and Normal Cells to Microbeam Radiation in the Absence of FLASH Effects. Cancers, 13(13), 3238.

Treatment planning is an essential step before any state-of-the-art radiotherapy treatment: It is required to estimate tumour control and potential side effects in organs at risk. In our team we develop innovative methods for dose calculation and biologically motivated treatment planning in spatially fractionated radiation therapy.

Part of the teams work is the implementation of fast and accurate dose calculation methods and a detailed characterization of source parameters. Together with partners at the Australian Synchrotron, we embedded these tools in a professional treatment planning system and we are now adapting it to our compact microbeam sources. The developed tools are used for retrospective treatment planning studies with the aim to establish the relevant field parameters and identify patient cohorts for first clinical applications in microbeam radiation therapy.

Dosimetry and quality assurance with micrometre sized beams is challenging. We established film dosimetry protocols with microscopic read-out and test various high-resolving dosimeters for future clinically relevant quality assurance protocols. 

Publications:

• Bartzsch, S., Ahmed, M., Bicher, S., Stewart, R. D., Schmid, T. E., Combs, S. E., & Meyer, J. (2023). Equivalent Uniform Dose (EUD) and the Evaluation of Cell Survival in Spatially Fractionated Radiotherapy (SFRT). International Journal of Radiation Oncology, Biology, Physics, 117(2), e642.
• Kraus, K. M., Winter, J., Zhang, Y., Ahmed, M., Combs, S. E., Wilkens, J. J., & Bartzsch, S. (2022). Treatment Planning Study for Microbeam Radiotherapy Using Clinical Patient Data. Cancers, 14(3), 685.
• Hombrink G, Wilkens JJ, Combs SE, Bartzsch S, "Simulation and measurement of microbeam dose distribution in lung tissue." Physica Medica 75 (2020): 77-82.
• Donzelli, M., Brauer-Krisch, E., Oelfke, U., Wilkens, J. J., & Bartzsch, S. (2018). Hybrid dose calculation: a dose calculation algorithm for microbeam radiation therapy. Physics in Medicine and Biology