Abstract
Purpose: In ion beam therapy electronic stopping power data enter in different disciplines, e.g., dose planning, dosimetry, and radiobiology. However, relevant stopping power data are only known within an accuracy of 2%-10%. We started the software library project libdEdx to unify data from several well-known stopping power sources into one ready-to-use package being 1) freely available and 2) easy accessible via a web-based front end.Methods: Currently, stopping power data from PSTAR, ASTAR, MSTAR and ICRU49+73 are implemented along with a version of the Bethe formula. The library is programmed in the language C to provide broad portability and high performance. A clean API provides full access to the underlying functions and thread safety in multi-threaded applications. The possibility to define arbitrary materials complements the list of predefined ICRU materials. Furthermore, we introduced a collection of tools, e.g., inverse stopping power look-up as well as CSDA range calculation and its inverse.Results: On a standard desktop PC libdEdx calculates 22 million look-ups/sec. A web GUI (available at http://dedx.au.dk) provides easy access to libdEdx and download of stopping data and graphs. For compounds, we observe that stopping power data are robust for variations in the mean excitation potential of the constituents as long as the total mean excitation potential is fixated.Conclusion: We released libdEdx (version number 1.2.1: http://sf.net/projects/libdedx/) with a web-based GUI. Future development will focus on implementing further stopping powers sources (e.g., for electrons and nuclear stopping) and relativistic effects.
Highlights
The energy loss of charged particles has extensively been researched for almost a century
Penetration ranges can be derived in the continuous slowing down approximation (CSDA), but uncertainties in the mean excitation potential lead to range uncertainties [1]
E.g., for ionization chamber dosimetry, in the evaluation of beam quality correction factors, where the dose in the ionization chamber wall material is translated to dose-to-water using stopping power ratios, as described in dosimetry protocols such as IAEA TRS-398 [2]
Summary
The energy loss of charged particles has extensively been researched for almost a century. Medical physics rely on electronic stopping powers in several ways. Dose is reported as dose-to-water while Monte Carlo particle transport codes calculate the dose deposited in the simulated medium, which might be different from water. The translation is done by calculating the stopping power ratio of the two media in the corresponding fluence spectrum. Radiobiology models that describe the response of in vitro cell cultures exposed to ion or neutron radiation rely on stopping powers [6, 7] in similar ways as numerous detector response models [8,9,10,11] do
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