Durante, M.

Eichhorn, A.

Krämer, M.

La Tessa, C.

Parodi, K.

Scifoni, E.

GSI Repository

Comparison between different dose calculation algorithms available in TRiP98and between the beam model of HIT and GSIA. Eichhorn1,2, C. La Tessa1,3, E. Scifoni1, M. Kra¨mer2, K. Parodi5,4, and M. Durante1,21GSI, Darmstadt, Germany; 2TU Darmstadt, Germany; 3BNL, New York, USA; 4Heidelberg University Hospital,Heidelberg, Germany; 5LMU Mu¨nchen, GermanyLast year the dose profiles behind thick bone-like targetsand interfaces between bone-like material and water in theentrance channel were studied [1]. The experiment wasperformed at the ’Heidelberger Ion-Beam Therapy Center’(HIT) and the experimental results were compared withdifferent simulations of the Treatment Planning System(TPS), TRiP98 [3]. The aim of the experiment was to val-idate TRiP98 for cases with thick inhomogeneous materialin the beam entrance channel.TRiP98 dose calculation algorithmsTRiP98 was developed at GSI for the radiotherapy pi-lot project and is constantly updated and used as a re-search prototype. The program performs physical and bio-logical dose calculations and optimizations, amongst othertasks. The aim of the optimization process is to deliver theprescribed dose as homogeneously as possible in the tu-mor volume and, simultaneously, to reduce the dose in thehealthy tissue and especially in the Organs At Risk (OAR).The calculation of the physical dose distribution canbe performed by three different implemented algorithms,which can be used for treatment planning. The classicalone (CL) uses a fast interpolation technique between the4 beam raster points neighbouring a CT voxel [2]. It of-fers very fast overview calculations but is less precise at theedges of the dose distribuition. A more advanced algorithmis all-points (AP). In contrast to the CL algorithm all pointsin the neighborhood are considered and the actual Gaussianshape of each beam spot is considered. AP is more precisethan the CL algorithm, but also more time consuming. Thelatest and most precise one is multiple scattering (MS) [4].For the MS algorithm the dose calculation is identical withthe AP one, but the beam broadening with increasing depthis taken into account by adding a second Gaussian with aFWHM reflecting multiple coulomb scattering and nuclearangular distributions. AP and MS can be enhanced by ac-counting for the divergence of the beam as it exits the beampipe (APDB and MSDB).ResultsThe treatment plans for the experiment at HIT wereoptimized with the APDB algorithm, since base data forthe more advanced MSDB algorithm was not available atthis time. Hence small deviation between the measureddata and the treatment planning were found. Recalcula-tions with MSDB was performed with a HIT-specific pencilbeam data base as soon as it became available [5]. Differ-ences between the calculations with MSDB and APDB forthe HIT-specific base data are shown in figure 1.0204060801000 50 100 150 200 250x [mm]Depth [mm]00.511.52x [mm]0 20 40-20-40Dose [Gy]00.511.522.5TumorBoneFigure 1: Comparision between the two different algo-rithms apdb and msdb of the HIT beam model and the mea-sured data.Therefore a precise recalculation of data measured atHIT is now possible with TRiP98.In addition it is shown in [6], that the differences in thebeam models of GSI and HIT are negligible and play noimportant role for recalculations.References[1] A.Eichhorn et al., ’Carbon beam dosimetry in bony tissueinhomogeneities: TRiP98 validation with experimental mea-surements’, GSI Scientific Report 2012 p. 460, (2013)[2] M. Kra¨mer et al., ’Treatment planning for heavy-ion radio-therapy:physical beam model and dose optimization’, Phys.Med. Biol., vol. 45(11), (2000)[3] M. Kra¨mer et al., ’Ion beam transport calculations and treat-ment plans in particle therapy’, Eur. Phys. J. D 60(95), (2010)[4] G. Iancu et al., ’Analysis of the multiple scattering implemen-tation in TRiP’, GSI Scientific Report 2006 p. 362, (2007)[5] K. Parodi et al., ’Monte Carlo-based parametrization of thelateral dose spread for clinical treatment planning of scannedproton and carbon ions beams’, J. Radiat. Res. vol. 54, (2013)[6] A. Eichhorn, ’Investigation of dose profile inhomogeneities atthe interface between water and bone-like materials follow-ing irradiaiton with therapeutic carbon ions’, Masterthesis,TU Darmstadt, Germany (2013)GSI SCIENTIFIC REPORT 2013 BIOPHYSICS-29doi:10.15120/GR-2014-1-BIOPHYSICS-29 231

Comparison between different dose calculation algorithms available in TRiP98 and between the beam model of HIT and GSI

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Comparison between different dose calculation algorithms available in TRiP98 and between the beam model of HIT and GSI

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