Present status and validation of HIBRAC Lembit Sihver a, b , Davide Mancusi a, * a Nuclear Engineering, Applied Physics, Chalmers University of Technology, Gothenburg, Sweden b Department of Mathematics, Computer Science and Physics, Roanoke College, Salem, VA, USA article info Article history: Received 8 January 2008 Received in revised form 21 November 2008 Accepted 26 November 2008 PACS: 87.53.Pb 87.53.Vb Keywords: Radiotherapy Heavy ions Transport codes: deterministic abstract This paper describes in detail the latest version of HIBRAC, a computer code to calculate one-dimensional deterministic particle transport, designed for application in treatment-planning systems when using highly energetic ions for radiotherapy. HIBRAC can calculate dose, dose-average LET (Linear Energy Transfer), track-average LET, fluence and energy distributions as a function of the penetration depth of light ion beams in any solid and fluid target material. The validity of the code is verified against measured dose and fluence distributions. The code shows good agreement for all the systems studied. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction In order to estimate the biological effect of highly energetic ions, accurate knowledge of the physics of their interaction with matter is necessary. This knowledge is especially important in radio- therapy, where the main purpose is to maximise the conformation of the delivered dose to the prescribed target volume while at the same time minimising the amount of damage sustained by the healthy tissue and other surrounding critical structures. The dose delivery of ions as a function of the penetration depth culminates in a steep maximum (the Bragg peak) and falls off rather quickly at larger depths. Compared to conventional proton beams, ions exhibit sharper physical dose distributions (since lateral and range straggling decreases quadratically with atomic number) and have a more favourable relative biological effectiveness (RBE) coefficient, allowing treatment of radio-resistant tumours with a high repair capacity against photon beams, even in hypoxic conditions (Amaldi and Kraft, 2005, and references therein); on the other hand, proton beams exhibit usually a sharper dose fall-off after the Bragg peak (BP) since they are not affected by projectile fragmentation. In fact, nuclear reactions between ions and matter produce highly ener- getic secondary fragments that reach well beyond the BP and that yield a complex beam composition. Increased interest on the use of ions for radiotherapy in the eighties resulted in the construction of the HIMAC (Heavy Ion Medical Accelerator in Chiba, Kawachi et al., 1989; Sato et al., 1992; Hirao et al., 1992; Kanai et al., 1992) at the National Institute for Radiological Sciences (NIRS) in Chiba, Japan, and the HIBMC (Hyogo Ion Beam Medical Centre, Kagawa et al., 2002) in Hyogo, Japan. The Gesellschaft fu ¨ r Schwerionenforschung (GSI) ion-physics research facility in Darmstadt, Germany, initiated clinical treatments also with carbon ions in 1997 (Kraft, 1990; Kraft et al., 1991; Kraft et al., 1995; Kraft, 2000) and a clinical facility is presently under construction in Heidelberg. Institute of Modern Physics (IMP) in Lanzhou, China, started treating skin cancer in November 2006 and plan to start treating also deep seated tumours during 2008. Light ions (Z < 10) achieve the best compromise between therapeutical effectiveness and preservation of the healthy tissue (Amaldi and Kraft, 2005), and in fact carbon has dominated the clinical appli- cations at HIMAC, HIBMC and GSI. Even a light ion like carbon, however, is affected by projectile fragmentation at the energies necessary for therapy. Since different fragments have different biological efficiencies and different dose distributions, it is crucial that the beam composition be known at all depths in order to estimate reliably the total biological efficiency of the beam. This problem is resolved by using a physical beam model which can calculate fluence distributions for all ion species in both the tumour and the healthy tissue. Traditionally, the physical beam model is a fast one-dimensional deterministic transport code; however, the scientific community has recently begun to regard three-dimensional Monte-Carlo * Corresponding author. Present address: Fundamental Interactions in Physics and Astrophysics, University of Lie `ge, 4000 Lie ` ge, Belgium. E-mail address: d.mancusi@ulg.ac.be (D. Mancusi). Contents lists available at ScienceDirect Radiation Measurements journal homepage: www.elsevier.com/locate/radmeas 1350-4487/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.radmeas.2008.11.004 Radiation Measurements 44 (2009) 38–46