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Evaluation of nuclear reaction cross-sections and fragment yields in carbon beams using the SHIELD-HIT Monte Carlo code. Comparison with experiments
Stockholm University, Faculty of Science, Department of Physics.
Stockholm University, Faculty of Science, Department of Physics.
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2012 (English)In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 57, no 13, 4369-4385 p.Article in journal (Refereed) Published
Abstract [en]

In light ion therapy, the knowledge of the spectra of both primary and secondary particles in the target volume is needed in order to accurately describe the treatment. The transport of ions in matter is complex and comprises both atomic and nuclear processes involving primary and secondary ions produced in the cascade of events. One of the critical issues in the simulation of ion transport is the modeling of inelastic nuclear reaction processes, in which projectile nuclei interact with target nuclei and give rise to nuclear fragments. In the Monte Carlo code SHIELD-HIT, inelastic nuclear reactions are described by the Many Stage Dynamical Model (MSDM), which includes models for the different stages of the interaction process. In this work, the capability of SHIELD-HIT to simulate the nuclear fragmentation of carbon ions in tissue-like materials was studied. The value of the parameter., which determines the so-called freeze-out volume in the Fermi break-up stage of the nuclear interaction process, was adjusted in order to achieve better agreement with experimental data. In this paper, results are shown both with the default value k = 1 and the modified value k = 10 which resulted in the best overall agreement. Comparisons with published experimental data were made in terms of total and partial charge-changing cross-sections generated by the MSDM, as well as integral and differential fragment yields simulated by SHIELD-HIT in intermediate and thick water targets irradiated with a beam of 400 MeV u(-1) C-12 ions. Better agreement with the experimental data was in general obtained with the modified parameter value (k = 10), both on the level of partial charge-changing cross-sections and fragment yields.

Place, publisher, year, edition, pages
2012. Vol. 57, no 13, 4369-4385 p.
National Category
Radiology, Nuclear Medicine and Medical Imaging
Research subject
Medical Radiation Physics
Identifiers
URN: urn:nbn:se:su:diva-80430DOI: 10.1088/0031-9155/57/13/4369ISI: 000305803600019OAI: oai:DiVA.org:su-80430DiVA: diva2:556150
Note

AuthorCount:6;

Available from: 2012-09-24 Created: 2012-09-19 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Secondary absorbed dose distributions and radiation quality in light ion therapy
Open this publication in new window or tab >>Secondary absorbed dose distributions and radiation quality in light ion therapy
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Radiotherapy with light ions offers the possibility of achieving a dose distribution which is highly conformed to the target volume while sparing normal tissues. For ions heavier than protons, an additional advantage is the increased Relative Biological Effectiveness (RBE) as compared to conventional photon and electron beams. During light ion therapy, nuclear fragments are produced in nuclear inelastic collisions of the projectile and the atomic nuclei in the material. In a cascade of events, the nuclear fragments in turn produce secondaries during their transport. The organs of the patient are thus exposed to a complex secondary radiation field and secondary doses can be delivered to normal tissues both close to and relatively far from the treated volume. In this thesis, secondary doses were evaluated in anthropomorphic phantoms which were developed for simulations with the Monte Carlo code SHIELD-HIT. Simulations of lung tumor, prostate and brain tumor irradiation with 1H, 4He, 7Li, 12C and 16O ion beams in the energy range 80-400 MeV/u were performed with SHIELD-HIT. The simulated organ absorbed doses were in the range 10-6-10-1 mGy per treatment Gy. In general, the organ absorbed doses decreased with increasing distance from the target volume and increased with increasing atomic number of the primary ions.

The produced nuclear fragments also influences the radiation quality in the target volume and thus the biological effectiveness of the beam. The dose-mean lineal energy, <yD>, was studied in a 290 MeV/u 12C beam by simulating the energy distributions of both primary and secondary ions and weighting their relative dose fractions with the corresponding energy-dependent <yD> which were obtained by ion-track simulations with PITS99 coupled with the electron transport code KURBUC. <yD> were evaluated in the target volume for object diameters 10-100 nm and were used in estimations of clinically useful weighting factors.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2011. 54 p.
Keyword
secondary doses, light ion therapy, radiation quality, Monte Carlo simulation
National Category
Physical Sciences
Research subject
Medical Radiation Physics
Identifiers
urn:nbn:se:su:diva-64302 (URN)978-91-7447-412-1 (ISBN)
Public defence
2011-12-20, Föreläsningssalen, Cancercentrum Karolinska, R8:00, Karolinska universitetssjukhuset, Solna, 13:00 (English)
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Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Submitted.

Available from: 2011-11-28 Created: 2011-11-16 Last updated: 2016-01-18Bibliographically approved

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