Berlin 2024 – wissenschaftliches Programm

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ST: Fachverband Strahlen- und Medizinphysik

ST 8: Accelerators for Medical Applications (joint session ST/AKBP)

ST 8.1: Vortrag

Donnerstag, 21. März 2024, 09:30–09:45, PC 203

Investigation of the track structure of therapeutic carbon ion radiation at HIT using the PTB ion counting nanodosimeter. — •Miriam Schwarze, Hans Rabus, and Gerhard Hilgers — Physikalisch-Technische Bundesanstalt, Germany

Nanodosimetry characterizes charged particle track structure and its biological effectiveness by the frequency distribution of ionizations in a given target, the ionization cluster size distribution (ICSD). First measurements of ICSDs were performed with the PTB Ion Counter nanodosimeter with therapeutic 12C ions at HIT.

The nanodosimeter was operated behind a PMMA collimator and PMMA absorbers of different thickness. Ionizations in the target were recorded in coincidence with the signals from two silicon strip detectors to determine the dependence of ICSDs on the impact parameter of the ions to the target.

Measurements with different absorber thickness and beam energy, combined such as to give an energy of 1 GeV in the target, produced mean ICSD values (M1) varying by almost 50 % over the investigated beam energy range for all impact parameters. Experiments with fixed beam energy and varying absorber thickness showed significantly higher M1 values than expected from previously measured data at lower energies [1].

A simulation of the measurement setup by the simulation software Geant4 was used to determine whether these deviations are caused by secondary particles.

[1] G. Hilgers et al., Phys. Med. Biol. 62 (2017) 7569-97

Keywords: Nanodosimetry; Ion Therapy