Durante, M.

Kraft-Weyrather, W.

Krämer, M.

Maier, A.

Scifoni, E.

Tinganelli, W.

GSI Repository

Experimental verification of TRiP-OER ∗E. Scifoni † 1, W. Tinganelli1,2, W. Kraft-Weyrather1, M. Durante1,2,3, A. Maier1, and M. Kra¨mer11GSI, Darmstadt, Germany; 2IOL GSI-NIRS, Chiba, Japan; 3TUD, Darmstadt, GermanyOne of the key challenges for advanced radiotherapyis the possibility to adapt the treatment to patient-specificfeatures, i.e. to perform an adaptive treatment planning.Among these features, increased radioresistence of tumorregions due to hypoxia (lower degree of cells’ oxigenation)assumes a crucial importance, given the extremely poorprognosis connected with this phenomenon. Ion beam ra-diation allows in principle a larger flexibility and a higherpotential for achieving an efficient adaptive treatment plan-ning, but specific tools are lacking.The TRiP98 code [1], pioneer treatment planning systemfor ion beams, which contributed to the success of the GSIpilot therapy project, was then recently extended towardthis direction, and specifically, to implement the biolog-ical optimization including the hypoxia-induced radiore-sistence, i.e., the oxygen enhancement ratio (OER).Figure 1: Experimental setup (see text).The TRiP-OER extension mainly consist in the possi-bility to introduce a selective treatment of differently oxy-genated areas of a tumor, once its spatial oxygenation mapis provided as an input (e.g. exploiting the recent PET func-tional imaging techniques [2]), through an effect-based op-timization aiming at restoring a prescribed survival level inthe overall tumor. The extension relies on a semiempiri-cal model description of the OER as a function of LET andoxygen concentration (pO2) [3], and the modification ofthe biological effect calculations introduced into the code∗Work supported by the European Commission under FP7 GrantAgreement Number 228436, project ULICE† e.scifoni@gsi.deand allowing to perform not only forward but also inverseplanning, obtaining an effective OER driven optimization[4,5].Dedicated experiments were then designed to verify theexpected survival predicted by the code in a carbon ion ex-tended target irradiation, and specifically, with a focus onthe very last part of the extended volume, where the LETeffect in suppressing the OER is maximum and has a steepgradient. This has been done by exposing CHO-K1 cellsin the GSI patented hypoxic triple ring chambers [6] in asequence designed to cover densely the relevant depth re-gion (Fig.1): the chambers containing the rings filled withmedium were exposed to the beam by a conveyor belt inanoxic and normoxic conditions.The experiments, performed during several carbonbeamtimes in 2011 and 2012, returned, despite a consistentexperimental uncertainty, a remarkable agreement with thecalculations of TRiP-OER (Figure 2).60 70 80 90 100 110depth in water (mm)11.522.53OER Figure 2: TRiP-OER computed OER values across a singlefield extended target irradiation (line) and correspondingexperimental data (points).References[1] M. Kramer and M. Durante, Eur. Phys. J. D. 60 (2010) 195.[2] S. M. Bentzen and V. Gregoire, Semin Radiat Oncol 21, 101(2011).[3] E. Scifoni, M. Kra¨mer and M. Durante, GSI Sci. Rep. 2011(2012) 521.[4] M. Kra¨mer, E. Scifoni, C. Wa¨lzlein and M. Durante, J. Phys.Conf. Ser. 373 (2012) 012017.[5] E. Scifoni, W. Tinganelli, W. Kraft-Weyrather, M. Durante,A. Maier and M. Kra¨mer, Phys. Med. Biol., submitted.[6] C. Schicker et al., Pat Ep 09002 402 (2009), 7.GSI SCIENTIFIC REPORT 2012 HEALTH-43467

Experimental verification of TRiP-OER

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Experimental verification of TRiP-OER

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