Treatment Planning and Validation
Group leader: PD Dr. Michael Krämer
This work group studies the interaction of charged particle beams, in particular carbon ions, with matter on multiple scales.
On the microscopic/nanoscopic - scale one has to consider elementary interactions to describe energy and damage deposition. For this purpose, we use the homegrown Monte Carlo code TRAX, which describes the production and transport of secondary electrons produced by heavy ions in matter (Figure 1). Recently, the ability to deal with dose enhancements by heavy atom nanoparticles under ion irradiation has been added (Figures 2).
- Ref.: Wälzlein C., Scifoni E., Krämer M., Durante M., Simulations of dose enhancement for heavy atom nanoparticles irradiated by protons Phys. Med. Biol., 59 (6):1441-1458 (2014); DOI: 10.1088/0031-9155/59/6/1441
Currently, radiation chemistry is being implemented, mainly aiming at the variation of the Oxygen Enhancement Ratio seen with high LET radiation.
Macroscopic dose distribution
On the macroscopic scale, mainly for the purpose of treatment planning, we run a homegrown numerical transport model. It considers electromagnetic and nuclear interactions with empirical corrections for the attenuation of the primary beam as well as for the creation of nuclear fragments. This model is implemented in our treatment planning code, TRiP98. We further use the Local Effect Model (LEM) to calculate and optimize RBE-weighted ("biological') dose distributions (Figure 3).
TRiP98 was in clinical use in the GSI pilot project. Siemens chose it as a prototype for their commercial SynGo PT TPS. Nowadays it serves as a research prototype inside and outside GSI to support new developments in ion beam radiotherapy.Recently support for alternative ions such as 16O and 4He (Figures 4) has been added.
- Ref.: Krämer M., Scifoni E., Schuy C., Rovituso M., Tinganelli W., Maier A., Kaderka R., Kraft-Weyrather W.K., Brons S., Tessonnier T., Parodi K., Durante M., Helium ions for radiotherapy? Physical and biological verifications of a novel treatment modality Med. Phys., 43 (4) :1995 -2004 (2016) PMID: 27036594, DOI: 10.1118/1.4944593
Moreover, optimization algorithms have been enhanced with the oxygen enhancement ratio (OER) as a driving force to allow the treatment of hypoxic tumour microenvironments via "kill-painting".
Experimental validation of treatment planning
We do not rely solely on simulations, but regularly perform radiobiological experiments in order to verify our predictions. The classical tools are cellular phantoms such as stacks andthe Biophantom in order to measure one- and twodimensional distributions of cell survival under patient-like conditions (Figures 5).
- Ref: Gemmel A., Hasch B., Ellerbrock M., Weyrather W.K., Krämer M., Biological dose optimization with multiple ion fields Phys. Med. Biol., 53 (23):6991-7012 (2008); DOI: 10.1088/0031-9155/53/23/022
A more recent development are the so-called hypoxia chambers, which allow irradiations under controlled oxygen concentrations. This way the "kill-painting" approach could be verified experimentally as a proof of concept (Figures 6).
- Ref.: Tinganelli W., Durante M., Hirayama R., Krämer M., Maier A., Kraft-Weyrather W.K., Furusawa Y., Friedrich T., Scifoni E., Kill-painting of hypoxic tumours in charged particle therapy; Scientific Reports, 5:Article number: 17016 (2015); DOI: doi:10.1038/srep17016
Main research topics
- Macroscopic dose distribution
- Adaptive treatment planning
- "Kill-painting" (e.g. to treat hypoxic tumours)
- Mathematical optimization algorithms
- Extension of TRiP98 to other ions
- Extension of TRiP98 to higher (Fair) energies, i.e. in the non-Bragg regime
- "Space TRiP": could we leverage radiotherapy planning concepts for space applications (very heavy ions, very high energies)?
- Microscopic calculations
- Low energy electron interactions
- Transport in inhomogenous media
- Nanoparticles and electron emission from solids
- Oxygen Effect
- Experimental validation of treatment planning
- Verification of 3D dose distributions
- Biological verification using 3D cellular phantoms
- Biological phantoms with different oxygen concentrations
- Tests of adaptive treatment plans
- DKFZ Heidelberg (Prof. O. Jäkel)
- HIT Heidelberg (Prof. T. Haberer
- Uni Marburg (Prof. K. Zink)
- Med. Uni Wien (Prof. D. Georg)
- CNAO Pavia (Prof. S. Rossi)
- Hochschule Darmstadt (Dept. of Mathematics, Prof. A. Fischer)
- Uni Aarhus (Dr. Niels Bassler)
- Uni Namur (Prof. S. Lucas)
- PTB Braunschweig (Dr. V. Dangendorf)
- TIFPA/INFN (Prof. Durante, Dr. Scifoni)
Dr. Martina Fuß