Evaluation of in vitro irradiation setup: Designed for the horizontal beamline at the Danish Centre for Particle Therapy.

Abstract

Radiobiological experimental setups are challenged by precise sample positioning along depth dose profile, scattering conditions, and practical difficulties that must be addressed in individual designs. The aim of this study was to produce cell survival curves with several irradiation modalities, by using a setup designed at the Danish Centre for Particle Therapy (DCPT) for in vitro proton irradiations using a horizontal beam line and thereby evaluating the setups use for in vitro irradiations experiments. The setup is a water phantom suitable for in vitro research with multiple irradiation modalities, in particular the pencil scanning proton beam available from a horizontal experimental beamline. The phantom included a water tank of 39.0 × 17.0 × 20.5 cm. Cell survival-curves were produced using the cell line V79 Chinese hamster lung fibroblast cells (V79s) in biological triplicates of clonogenic assays. Cell survival curves were produced with both a 18 MeV electron beam, 6 MV photon beam, and a Spread-Out Bragg Peak (SOBP) proton beam formed by pristine energies of 85-111 MeV where three positions were examined. Survival curves with uncertainty areas were made for all modalities. Dosimetric uncertainty amounted to, respectively, 4%, 3% and 3% for proton, electron, and high energy photon irradiations. Cell survival fraction uncertainty was depicted as the standard deviation between replications of the experiment. Cell survival curves could be produced with acceptable uncertainties using this novel water phantom and cellular laboratory workflow. The setup is useful for future in vitro irradiation experiments.