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Analytical model for light ion pencil beam dose distributions: multiple scattering of primary and secondary ions
Stockholm University, Faculty of Science, Medical Radiation Physics (together with KI).
Stockholm University, Faculty of Science, Medical Radiation Physics (together with KI).
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2008 (English)In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 53, no 13, 3477-3491 p.Article in journal (Refereed) Published
Abstract [en]

An analytical algorithm based on the generalized Fermi–Eyges theory, amended for multiple Coulomb scattering and energy loss straggling, is used for calculation of the dose distribution of light ion beams in water. Pencil beam energy deposition distributions are derived for light ions by weighting a Monte Carlo (MC) calculated planar integral dose distribution with analytically calculated multiple scattering and range straggling distributions. The planar integral dose distributions are calculated using the MC code SHIELD-HIT07, in which multiple scattering and energy loss straggling processes are excluded. The contribution from nuclear reactions is included in the MC calculations. Multiple scattering processes are calculated separately for primary and secondary ions and parameters of the initial angular and radial spreads, and the covariance of these are derived by a least-square parameterization of the SHIELD-HIT07 data. The results from this analytical algorithm are compared to pencil beam dose distributions obtained from SHIELD-HIT07, where all processes are included, as well as to experimental data. The presented analytical approach allows for the accurate calculation of the spatial energy deposition distributions of ions of atomic numbers Z = 1 − 8.

Place, publisher, year, edition, pages
2008. Vol. 53, no 13, 3477-3491 p.
Keyword [en]
Medical physics, Biological physics
National Category
Physical Sciences
URN: urn:nbn:se:su:diva-25125DOI: 10.1088/0031-9155/53/13/005OAI: diva2:198967
Available from: 2008-05-14 Created: 2008-05-13 Last updated: 2011-02-17Bibliographically approved
In thesis
1. Absorbed dose and biological effect in light ion therapy
Open this publication in new window or tab >>Absorbed dose and biological effect in light ion therapy
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Radiation therapy with light ions improves treatment outcome for a number of tumor types. The advantageous dose distributions of light ion beams en-able exceptional target conformity, which assures high dose delivery to the tumor while minimizing the dose to surrounding normal tissues. The demand of high target conformity necessitates development of accurate methods to calculate absorbed dose distributions. This is especially important for heavy charged particle irradiation, where the patient is exposed to a complex radia-tion field of primary and secondary ions.

The presented approach combines accurate Monte Carlo calculations using the SHIELD-HIT07 code with a fast analytical pencil beam model, to pro-vide dose distributions of light ions. The developed model allows for ana-lytical descriptions of multiple scattering and energy loss straggling proc-esses of both primary ions and fragments, transported in tissue equivalent media. By applied parameterization of the radial spread of fragments, im-proved description of radial dose distributions at every depth is obtained. The model provides a fast and accurate tool of practical value in clinical work.

Compared to conventional radiation modalities, an enhanced tissue response is seen after light ion irradiation and biological optimization calls for accu-rate model description and prediction of the biological effects of ion expo-sure. In a joint study, the performance of some radiobiological models is compared for facilitating the development towards more robust and precise models. Specifically, cell survival after exposure to various ion species is modeled by a fast analytical cellular track structure approach in conjunction with a simple track-segment model of ion beam transport. Although the stud-ies show that descriptions of complex biological effects of ion beams, as given by simple radiobiological models, are approximate, the models may yet be useful in analyzing clinical results and designing new strategies for ion therapy.

Place, publisher, year, edition, pages
Stockholm: Medicinsk strålningsfysik (tills m KI), 2008. 67 p.
Light ion therapy, absorbed dose calculation, analytical pencil beam model, Monte Carlo, radiobiological modeling
National Category
Radiology, Nuclear Medicine and Medical Imaging
Research subject
Medical Radiation Physics
urn:nbn:se:su:diva-7756 (URN)978-91-7155-671-4 (ISBN)
Public defence
2008-06-05, föreläsningssalen, Radiumhemmet, Karolinska universitetssjukhuset, Solna, 09:15
Available from: 2008-05-14 Created: 2008-05-13 Last updated: 2013-08-12Bibliographically approved

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Gudowska, Irena
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ReferencesLink to record
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