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A Monte Carlo track structure simulation code for the full-slowing-down carbon projectiles of energies 1 keV u-1–10 MeV u-1 in water
Karolinska Institutet, Institutionen för onkologi-patologi .
Karolinska Institutet, Institutionen för onkologi-patologi .
2013 (English)In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 58, no 3, 673-702 p.Article in journal (Refereed) Published
Abstract [en]

The paper presents a new Monte Carlo track structure code (KURBUC_carbon) for simulations of full slowing down carbon projectiles C0–C6+ of energies 1 keV/u–10 MeV/u in water vapour. The code facilitates investigation of spatial resolution effect for scoring track parameters under the Bragg peak of carbon ion beam. Interactions of carbon projectiles and secondary electrons were followed event-by-event down to 1 keV/u cutoff for primary ions, and down to 10 eV for electrons. Electronic interactions and nuclear elastic scattering were taken into account, including charge exchange reactions and double electronic interactions for the carbon projectiles. The reliability of the code was tested for radial dose, range, and W-value. The calculated results were compared with the published experimental data, and other model calculations. The results obtained showed good agreement in most cases where comparisons could be made. Depth dose profiles for 1-10 MeV/u C6+ were used to form an SOBP of 0.35 mm width in water. At all depths of the SOBP, the energy distributions of the carbon projectiles varied appreciably with the change in the scoring volume. The corresponding variation was nearly negligible for the track average LET, except at the distal end of the SOBP. By varying the scoring slab thickness from 1 to 100 µm, the maximum track average LET decreased by ~30%. The Monte Carlo track structure simulation in the full slowing down mode is a powerful tool for investigation of biophysical properties of radiation tracks under the Bragg peak and SOBP of carbon ion beam. For estimation of radiation effectiveness under the Bragg peak the new Monte Carlo track structure code provides yet another accurate and effective dosimetry tool at a single cell level. This is because radiobiology within tissue elements can only be understood with dosimetry at cellular and subcellular level.

Place, publisher, year, edition, pages
2013. Vol. 58, no 3, 673-702 p.
Keyword [en]
Track structure, Monte Carlo simulations, carbon ions, Bragg peak, SOBP, dosimetry, LET, CTMC
National Category
Physical Sciences Other Computer and Information Science
Research subject
Medical Radiation Physics
Identifiers
URN: urn:nbn:se:su:diva-81453DOI: 10.1088/0031-9155/58/3/673OAI: oai:DiVA.org:su-81453DiVA: diva2:561738
Available from: 2012-10-21 Created: 2012-10-21 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Development of Monte Carlo track structure simulations for protons and carbon ions in water
Open this publication in new window or tab >>Development of Monte Carlo track structure simulations for protons and carbon ions in water
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The goal of radiation therapy is to eradicate tumour cells while minimising radiation dose to healthy tissues. Ions including protons and carbon ions have gained increasing interest for cancer treatment. Advantages of ion beam therapy are conformal dose distribution, and for ions heavier than protons increased biological effectiveness in cell killing, compared to conventional radiation therapy using photons. Despite these advantages, fundamental problems in ion beam therapy include accuracy of dose determination at the cellular level, and characterisation of the radiation quality at the microscopic scale. Due to the high density of interactions along ion tracks, inhomogeneity of dose and track parameters at the cellular level is one of the major concerns for ion beam therapy.

The aim of the thesis is to develop computational tools for dosimetry of ion tracks at the molecular level. Event-by-event Monte Carlo track structure (MCTS) simulations were developed for full-slowing-down tracks of protons and carbon ions in water representing cellular environment. In Paper I, the extension of the MCTS code KURBUC_proton was carried out to energies up to 300 MeV, covering the entire proton energy range used in radiation therapy. Physical properties and microdosimetry of proton tracks were investigated and benchmarked with the experimental data. Papers II-V describe the development of the MCTS code for full-slowing-down tracks of carbon ions. In Papers II-IV, the classical trajectory Monte Carlo (CTMC) model was developed for the calculation of interaction cross sections for low and intermediate energy carbon projectiles of all charge states (C0 to C6+) in water. In Paper V, the calculated cross sections were implemented in a new MCTS code KURBUC_carbon simulating carbon ions of energies 1-104 keV/u in water. This development allows the investigation of track parameters in the Bragg peak region of carbon ion beams.

Publication of the thesis and the published papers make contribution to the physics of ion interactions in matter, and provide a new and complete database of electronic interaction cross sections for low and intermediate energy carbon projectiles of all charge states in water. The MCTS codes for protons and carbon ions provide new tools for biophysical study, including microdosimetry, of ion tracks at cellular and subcellular levels, in particular in the Bragg peak region of these ions.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2012. 107 p.
Keyword
Radiation track structure, Monte Carlo simulations, interaction cross sections, classical trajectory Monte Carlo (CTMC) method, microdosimetry, ion beams
National Category
Physical Sciences
Research subject
Medical Radiation Physics
Identifiers
urn:nbn:se:su:diva-81461 (URN)978-91-7447-591-3 (ISBN)
Public defence
2012-11-30, Rondrum 1, Building A6, Floor 1 (A6:01), Nuclear Medicine Department, Karolinska University Hospital, Solna, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Submitted. Paper 5: Submitted.

 

Available from: 2012-11-08 Created: 2012-10-21 Last updated: 2017-11-22Bibliographically approved

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