title: The influence of reference radiation photon energy on high-LET RBE: comparison of human peripheral lymphocytes and human-hamster hybrid ALcells.
abstract: The relative biological effectiveness (RBE) based on the induction of dicentrics in any cell type is principally an important information for the increasing application of high-LET radiation in cancer therapy. Since the standard system of human lymphocytes for measuring dicentrics are not compatible with our microbeam irradiation setup where attaching cells are essential, we used human-hamster hybrid ALcells which do attach on foils and fulfil the special experimental requirement for microbeam irradiations. In this work, the dose-response of ALcells to photons of different energy, 70 and 200 kV X-rays and60Co γ-rays, is characterized and compared to human lymphocytes. The total number of induced dicentrics in ALcells is approximately one order of magnitude smaller. Despite the smaller α and β parameters of the measured linear-quadratic dose-response relationship, the α/β-ratio versus photon energy dependence is identical within the accuracy of measurement for ALcells and human lymphocytes. Thus, the influence of the reference radiation used for RBE determination is the same. For therapy relevant doses of 2 Gy (60Co equivalent), the difference in RBE is around 20% only. These findings indicate that the biological effectiveness in ALcells can give important information for human cells, especially for studies where attaching cells are essential.
authors.affiliation: Institute of Innovative Radiotherapy, Helmholtz Zentrum München, Munich, Germany. t.e.schmid@tum.de.|Klinikum rechts der Isar, Department of Radiation Oncology, Technische Universität München, 81675, Munich, Germany. t.e.schmid@tum.de.
authors.forename: T E
authors.initials: TE
authors.lastname: Schmid
authors.affiliation: Institute for Applied Physics and Metrology, Universität der Bundeswehr München, 85577, Neubiberg, Germany.
authors.forename: C
authors.identifier: 0000-0001-6625-4837
authors.initials: C
authors.lastname: Greubel
authors.affiliation: Institute for Applied Physics and Metrology, Universität der Bundeswehr München, 85577, Neubiberg, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Dollinger
authors.affiliation: BioMedizinisches Centrum, Lehrstuhl Zellbiologie, Anatomie III, University of Munich, 80336, Munich, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Schmid
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D006822:Hybrid Cells / Q000166:cytology / Q000528:radiation effects*; D042541:Intracellular Space / Q000528:radiation effects; D018499:Linear Energy Transfer; D008214:Lymphocytes / Q000166:cytology / Q000528:radiation effects*; D017785:Photons; D012015:Reference Standards; D012062:Relative Biological Effectiveness
keywords: LET; Lymphocytes; RBE; Radiation