Treatment planning for our rasterscan system means determining
the necessary energies, positions and intensities for the ion
beam spots which, when overlaid, should give a homogeneous
biological dose distribution
conforming to the target volume (tumour) as specified by the physician.
This task is equivalent to an optimization problem with up to
50000 degrees of freedom for the largest tumours.
A prerequisite is the availability of physical and biological models for the interaction of ions with living matter. The optimization procedures have to handle the nonlinear dependence of the relative biological effectiveness (RBE) on the absorbed physical dose.
All of this has been incorporated into our treatment planning computer program TRiP98
The conformity of a sample dose distribution can be visualized as shown in the following picture.
|A spherical volume of 6 cm diameter between 9 and 15 cm depth in water was irradiated with carbon ions of 270 MeV per nucleon. CR-39 nuclear track detectors were placed in water in steps of a few mm. After etching they show the precise delivery of dose in the target volume. Future developments will allow to incorporate the effects of inhomogeneous targets as well as the biological efficiency.|
Last update: January 29th 2003, M.Kraemer@gsi.de, Design: Marcus Winter, M.Winter@gsi.de