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Secondary doses delivered to an anthropomorphic male phantom under prostate irradiation with proton and carbon ion beams
Stockholm University, Faculty of Science, Department of Physics.
Stockholm University, Faculty of Science, Department of Physics.
2010 (English)In: Radiation Measurements, ISSN 1350-4487, E-ISSN 1879-0925, Vol. 45, no 10, 1410-1413 p.Article in journal (Refereed) Published
Abstract [en]

Secondary radiation exposure of patients undergoing radiation therapy with light ions is of great concern due to possible tissue damage and risk of induction of secondary cancers. Secondary particles such as neutrons, protons and heavier ions are produced when the primary ions interact through nuclear inelastic reactions with the beam-line components, and with the tissues of the patient. Evaluations of secondary doses delivered to an anthropomorphic male phantom under prostate irradiation with (1)H and (12)C ion beams with energies 172 MeV and 330 MeV/u, respectively, have been performed with the Monte Carlo code SHIELD-HIT. Fluences of secondary particles with atomic mass A = 1-7 and energies up to 200-600 MeV/u are observed in organs even at larger distances (40-50 cm) from the irradiated volume. The secondary absorbed doses in selected organs are discussed taking into account the dose contribution from secondary neutrons, and the contribution from charged fragments that are not the products of neutron interactions. For (12)C ion irradiation, a substantial contribution to the absorbed organ dose is due to charged fragments. This contribution decreases from 81% in the organs close to the irradiated volume to 35-40% in the organs at larger distances.

Place, publisher, year, edition, pages
2010. Vol. 45, no 10, 1410-1413 p.
Keyword [en]
Secondary doses, Ion radiotherapy, Monte Carlo simulations
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:su:diva-66219DOI: 10.1016/j.radmeas.2010.05.020ISI: 000286349000078OAI: oai:DiVA.org:su-66219DiVA: diva2:467695
Note
authorCount :2Available from: 2011-12-19 Created: 2011-12-19 Last updated: 2017-12-08Bibliographically 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)
Opponent
Supervisors
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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