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Physical and biophysical properties of proton tracks of energies 1 keV to 300 MeV in water
Karolinska Institutet, Institutionen för onkologi-patologi .
Kyushu University, School of Health Science.
University of Ioannina, Medical Physics Lab.
Karolinska Institutet, Institutionen för onkologi-patologi .
2011 (English)In: International Journal of Radiation Biology, ISSN 0955-3002, E-ISSN 1362-3095, Vol. 87, no 2, 141-160 p.Article in journal (Refereed) Published
Abstract [en]

Materials and methods: aEuro integral We present model calculations for cross sections and methods for simulations of full-slowing-down proton tracks. Protons and electrons were followed interaction-by-interaction to cut-off energies, considering elastic scattering, ionisation, excitation, and charge-transfer. Results: aEuro integral Model calculations are presented for singly differential and total cross sections, and path lengths and stopping powers as a measure of the code evaluation. Depth-dose distributions for 160 MeV protons are compared with experimental data. Frequencies of energy loss by electron interactions increase from similar to 3%% for 10 keV to similar to 77%% for 300 MeV protons, and electrons deposit aEuroS > 70%% of the dose in 160 MeV tracks. From microdosimetry calculations, 1 MeV protons were found to be more effective than 5--300 MeV in energy depositions greater than 25, 50, and 500 eV in cylinders of diameters and lengths 2, 10, and 100 nm, respectively. For lower-energy depositions, higher-energy protons are more effective. Decreasing the target size leads to the reduction of frequency- and dose-mean lineal energies for protons < 1 MeV, and conversely for higher-energy protons. Conclusions: aEuro integral Descriptions of proton tracks at molecular levels facilitate investigations of track properties, energy loss, and microdosimetric parameters for radiation biophysics, radiation therapy, and space radiation research.

Place, publisher, year, edition, pages
2011. Vol. 87, no 2, 141-160 p.
Keyword [en]
Monte Carlo simulation, track structure, proton, cross sections, microdosimetry
National Category
Physical Sciences
Research subject
Medical Radiation Physics
Identifiers
URN: urn:nbn:se:su:diva-81449DOI: 10.3109/09553002.2010.518204ISI: 000287087100003OAI: oai:DiVA.org:su-81449DiVA: diva2:561734
Available from: 2012-10-21 Created: 2012-10-21 Last updated: 2017-12-07
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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