uu.seUppsala University Publications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Energy deposition clustering as a functional radiation quality descriptor for modelling relative biological effectiveness
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Medical Radiation Science. (Anders Ahnesjö)
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Medical Radiation Science.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Medical Radiation Science.
2016 (English)In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 43, no 12, 6322-6335 p.Article in journal (Refereed) Published
Abstract [en]

Purpose: To explore the use of the frequency of the energy deposition (ED) clusters of different sizes (cluster order, CO) as a surrogate (instead of, e.g., LET) classification of the physical characteristics of ionizing radiation at a nanometer scale, to construct a framework for the calculation of relative biological effectiveness (RBE) with cell survival as endpoint.

Methods: The frequency of cluster order f(CO) is calculated by sorting the ED sites generated with the Monte Carlo track structure code LIonTrack into clusters based on a single parameter called the cluster distance d(C) being the maximum allowed distance between two neighboring EDs belonging to a cluster. Published cell survival data parameterized with the linear-quadratic (LQ) model for V79 cells exposed to 15 different radiation qualities (including brachytherapy sources, proton, and carbon ions) were used as input to a fitting procedure, designed to determine a weighting function w(CO) that describes the capacity of a cluster of a certain CO to damage the cell's sensitive volume. The proposed framework uses both f(CO) and w(CO) to construct surrogate based functions for the LQ parameters a and beta from which RBE values can be derived.

Results: The results demonstrate that radiation quality independent weights w(CO) exist for both the a and beta parameters. This enables the calculation of a values that correlate to their experimental counterparts within experimental uncertainties (relative residual of 15% for d(C) = 2.5 nm). The combination of both a and beta surrogate based functions, despite the higher relative residuals for beta values, yielded an RBE function that correlated to experimentally derived RBE values (relative residual of 16.5% for d(C) = 2.5 nm) for all radiation qualities included in this work.

Conclusions: The f(CO) cluster characterization of ionizing radiation at a nanometer scale can effectively be used to calculate particle and energy dependent a and beta values to predict RBE values with potential applications to, e.g., treatment planning systems in radiotherapy. (C) 2016 American Association of Physicists in Medicine.

Place, publisher, year, edition, pages
2016. Vol. 43, no 12, 6322-6335 p.
Keyword [en]
RBE, Monte Carlo track structure, linear-quadratic model, energy deposition clusters
National Category
Cancer and Oncology
Research subject
Medical Radiophysics
Identifiers
URN: urn:nbn:se:uu:diva-279240DOI: 10.1118/1.4966033ISI: 000390237200012OAI: oai:DiVA.org:uu-279240DiVA: diva2:907719
Funder
Swedish National Infrastructure for Computing (SNIC), p2011144Swedish Radiation Safety Authority
Available from: 2016-02-29 Created: 2016-02-29 Last updated: 2017-11-30Bibliographically approved
In thesis
1. Micro/nanometric Scale Study of Energy Deposition and its Impact on the Biological Response for Ionizing Radiation: Brachytherapy radionuclides, proton and carbon ion beams
Open this publication in new window or tab >>Micro/nanometric Scale Study of Energy Deposition and its Impact on the Biological Response for Ionizing Radiation: Brachytherapy radionuclides, proton and carbon ion beams
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Research in radiotherapy for cancer treatment focuses on finding methods that can improve the compromise between tumour cell inactivation versus damage to the surrounding healthy tissue. As new radiation modalities such as proton therapy become accessible for everyday clinical practice, a better understanding of the variation in biological response of the tumour and healthy tissues would improve treatment planning to achieve optimal outcome. The development of radiobiological models capable of accurate predictions of biological effectiveness is needed.

Existing radiation quality descriptors such as absorbed dose and LET are insufficient to explain variation in biological effectiveness for different treatment modalities. The stochastic nature of ionizing radiation creates discrete patterns of energy deposition (ED) sites which can now be analysed through sophisticated computer simulations (e.g. Monte Carlo track structure codes). This opens the possibility to develop a nanometre characterization of radiation quality based on the spatial cluster patterns of ED.

The aim of this thesis is to investigate the track structure (ED spatial pattern) properties of several radiation qualities at a micro- and nanometric scale while exploring their influence in biological response through correlations with published experimental data. This work uses track structure data simulated for a set of 15 different radiation qualities: 4 commonly used brachytherapy sources, 6 different proton energies, 4 different carbon ion energies, and 60Co photons used as reference radiation for quantification of biological effectiveness.

At a micrometre level, the behaviour of the microdosimetric spread in energy deposition for target sizes of the order of cell nuclei was analysed. The degree of the influence it had in the biological response was found to be negligible for photon sources but for protons and carbon ions the impact increased with decreasing particle energy suggesting it may be a confounding factor in biological response.

Finally, this thesis outlines a framework for modelling the relative biological effectiveness based on the frequency distribution of cluster order as a surrogate for the nanometre classification for the physical properties of radiation quality. The results indicate that this frequency is a valuable descriptor of ionizing radiation. The positive correlation across the different types of ionizing radiation encourages further development of the framework by incorporating the behavior of the microdosimetric spread and expanding tests to other experimental datasets.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 53 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1188
Keyword
Ionizing radiation, Monte Carlo track structure code, Microdosimetric spread, Energy deposition clustering, RBE
National Category
Cancer and Oncology
Research subject
Medical Radiophysics
Identifiers
urn:nbn:se:uu:diva-279385 (URN)978-91-554-9495-7 (ISBN)
Public defence
2016-04-22, Skoogssalen, Akademiska Sjukhuset, Ing. 78-79, Uppsala, 09:30 (English)
Opponent
Supervisors
Available from: 2016-04-01 Created: 2016-03-01 Last updated: 2016-04-05

Open Access in DiVA

No full text

Other links

Publisher's full text

Authority records BETA

Villegas, FernandaAhnesjö, Anders

Search in DiVA

By author/editor
Villegas, FernandaTilly, NinaAhnesjö, Anders
By organisation
Medical Radiation Science
In the same journal
Medical physics (Lancaster)
Cancer and Oncology

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 417 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf