Presenter of 1 Presentation
IN VITRO MEASUREMENTS OF PROTON RBE: A MULTI-CENTRIC COMPARISON OF EXPERIMENTAL PROCEDURES AND RESULTS
Abstract
Background and Aims
We present the current status and outcomes of the joint radiobiological experiment performed at eight European proton therapy centers or research institutes. The study aims to spot the potential differences in the in vitro proton RBE values measured by different groups sharing a similar setup and identify its causes.
Methods
A phantom and a protocol for sample preparation and post-processing are shared among the participants to ensure minimal differences in the biological part of the experimental procedure. In this phantom, V79 cells grow on the polyester slides that can be inserted at different depths, which enables their simultaneous irradiation at multiple positions within the radiation field. The setup is irradiated with proton beams with two SOBP configurations (6 cm, 6 Gy, and 4 cm, 8 Gy), followed by the reference photon irradiation (LINAC or x-ray), and the biological effect is evaluated using a colony-forming assay.
Results
The study is still ongoing, and the spread of data for measured cell survival is yet to be evaluated. However, some non-obvious differences in the experimental procedures and setups are already revealed, e.g. post-processing timing or varying dose distributions in the beam plateau/fall-off regions.
Conclusions
As an outcome of the experiment, we plan to summarize the details of the experimental procedure for biological experiments with proton beams, differing between the centers across Europe. Accounting for these details would help to harmonize future studies in the field.
This work was supported by EU Horizon2020 grant 730983 (INSPIRE).
Author Of 2 Presentations
ULTRA-HIGH DOSE RATE (FLASH) CARBON ION IRRADIATION: FIRST IN VITRO AND IN VIVO RESULTS
Abstract
Background and Aims
In this work, we present the results of first in vitro and in vivo studies for carbon ion beams irradiation that aim to investigate the biological effects delivered at ultra-high dose rate (FLASH).
Methods
The Heidelberg Ion-Beam Therapy Center (HIT) synchrotron, after technical adaptions, can reliably extract 5×108 12C ions within approximately 150 ms. This yields a dose of 7.5 Gy (homogeneity of ±5%) in a volume of at least 8 mm in diameter and a corresponding dose rate of 40-70 Gy s-1. Additionally, similar beam application but at 8 times higher beam intensity could be recently performed at GSI for carbon FLASH irradiations in mice models (Dose: 12-18 Gy, Dose-rate 60-100 Gy s-1).
Results
For the in vitro experiments a clonogenic survival assay and residual γH2AX foci analysis have been performed. The results of the survival assay demonstrate a significant FLASH sparing effect which is strongly oxygenation-dependent and is mostly pronounced at the concentration of 0.5% O2 but absent at 0% and 21% O2 (fig 1). The γH2AX results shows reduction in the residual foci signal at 1% O2.
The GSI in vivo irradiations of mice models could be successfully performed in the plateau and in the SOBP region (fig 2). The SIS18 synchrotron enables treatment of target volumes of typically 20 cm3 with 15 Gy in 150 ms. Larger volumes seem to be possible.
Conclusions
The in vitro experiments confirm FLASH sparing effect at low oxygen concentrations. The pre-clinical results from the very recent mice model experiments are currently under evaluation.
IN VITRO MEASUREMENTS OF PROTON RBE: A MULTI-CENTRIC COMPARISON OF EXPERIMENTAL PROCEDURES AND RESULTS
Abstract
Background and Aims
We present the current status and outcomes of the joint radiobiological experiment performed at eight European proton therapy centers or research institutes. The study aims to spot the potential differences in the in vitro proton RBE values measured by different groups sharing a similar setup and identify its causes.
Methods
A phantom and a protocol for sample preparation and post-processing are shared among the participants to ensure minimal differences in the biological part of the experimental procedure. In this phantom, V79 cells grow on the polyester slides that can be inserted at different depths, which enables their simultaneous irradiation at multiple positions within the radiation field. The setup is irradiated with proton beams with two SOBP configurations (6 cm, 6 Gy, and 4 cm, 8 Gy), followed by the reference photon irradiation (LINAC or x-ray), and the biological effect is evaluated using a colony-forming assay.
Results
The study is still ongoing, and the spread of data for measured cell survival is yet to be evaluated. However, some non-obvious differences in the experimental procedures and setups are already revealed, e.g. post-processing timing or varying dose distributions in the beam plateau/fall-off regions.
Conclusions
As an outcome of the experiment, we plan to summarize the details of the experimental procedure for biological experiments with proton beams, differing between the centers across Europe. Accounting for these details would help to harmonize future studies in the field.
This work was supported by EU Horizon2020 grant 730983 (INSPIRE).