Change search
ReferencesLink to record
Permanent link

Direct link
Relative biological effectiveness of 50-MV X-rays on jejunal crypt survival in vivo
Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation biology.
Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
1992 (English)In: Radiation Research, ISSN 0033-7587, Vol. 132, no 1, 112-114 p.Article in journal (Refereed) Published
Abstract [en]

Earlier in vitro studies of relative biological effectiveness (RBE) of 50-MV X rays show an RBE of approximately 1.1 compared to 4 MV. No difference in RBE has been found for 20-MV X rays or 50-MeV electrons. The higher RBE for 50 MV can be explained to some extent by the small high linear energy transfer contribution from photonuclear reactions at high X-ray energies. To investigate the validity of the results in vitro, a study of the RBE of 50-MV X rays has been performed in vivo using the jejunal crypt microcolony assay in mice. The reference radiation used in this case was 20-MV X rays. The results confirm the earlier in vitro studies. The RBE for 50-MV X rays was estimated to be 1.06, calculated as the ratio between the slopes of the response curves.

Place, publisher, year, edition, pages
Oak Brook, IL 60521 USA: Radiation Research Society , 1992. Vol. 132, no 1, 112-114 p.
National Category
Cancer and Oncology
URN: urn:nbn:se:umu:diva-39967DOI: 10.2307/3578341ISI: A1992JU54700016OAI: diva2:396933
Available from: 2011-02-11 Created: 2011-02-11 Last updated: 2014-12-16Bibliographically approved
In thesis
1. Biological effects of high energy radiation and ultra high dose rates
Open this publication in new window or tab >>Biological effects of high energy radiation and ultra high dose rates
1991 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Recently a powerful electron accelerator, 50 MeV race-track microtron, has been taken into clinical use. This gives the opportunity to treat patients with higher x-ray and electron energies than before. Furthermore, treatments can be performed were the entire fractional dose can be delivered in parts of a second.

The relative biological effectiveness (RBE) of high energy photons (up to 50 MV) was studied in vitro and in vivo. Oxygen enhancement ratio (OER) of 50 MV photons and RBE of 50 MeV electrons were investigated in vitro. Single-fraction experiments, in vitro, using V-79 Chinese hamster fibroblasts showed an RBE for 50 MV x-rays of approximately 1.1 at surviving fraction 0.01, with reference to the response to 4 MV x- rays. No significant difference in OER could be demonstrated. Fractionation experiments were carried out to establish the RBE at the clinically relevant dose level, 2 Gy. The RBE calculated for the 2 Gy/fraction experiments was 1.17. The RBEs for 20 MV x-rays and 50 MeV electrons were equal to one. In order to investigate the validity of these results, the jejunal crypt microcolony assay in mice was used to determine the RBE of 50 MV x-rays. The RBE for 50 MV x-rays in this case was estimated to be 1.06 at crypt surviving fraction 0.1. Photonuclear processes are proposed as one possible explanation to the higher RBE for 50 MV x-rays.

Several studies of biological response to ionizing radiation of high absorbed dose rates have been performed, often with conflicting results. With the aim of investigating whether a difference in effect between irradiation at high dose rates and at conventional dose rates could be verified, pulsed 50 MeV electrons from a clinical accelerator were used for experiments with ultra high dose rates (mean dose rate: 3.8 x 10^ Gy/s) in comparison to conventional (mean dose rate: 9.6 x 10"^ Gy/s). V-79 cells were irradiated in vitro under both oxic and anoxic conditions. No significant difference in relative biological effectiveness (RBE) or oxygen enhancement ratio (OER) was observed for ultra high dose rates compared to conventional dose rates.

A central issue in clinical radiobiological research is the prediction of responses to different radiation qualities. The choice of cell survival and dose response model greatly influences the results. In this context the relationship between theory and model is emphasized. Generally, the interpretations of experimental data are dependent on the model. Cell survival models are systematized with respect to their relations to radiobiological theories of cell kill. The growing knowledge of biological, physical, and chemical mechanisms is reflected in the formulation of new models. This study shows that recent modelling has been more oriented towards the stochastic fluctuations connected to radiation energy deposition. This implies that the traditional cell survival models ought to be complemented by models of stochastic energy deposition processes at the intracellular level.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 1991. 44 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 315
Radiobiology, 50 MV x-rays, 50 MeV electrons, in vitro, in vivo, RBE, OER, ultra high dose-rate, radiobiological models, model selection, models of stochastic processes
National Category
Cancer and Oncology
urn:nbn:se:umu:diva-96889 (URN)91-7174-614-5 (ISBN)
Public defence
1991-11-21, Onkologiska klinikens föreläsningssal, 244, 2 tr., Umeå universitet, Umeå, 09:00

S. 1-44: sammanfattning, s. 47-130: 5 uppsatser

Available from: 2014-12-16 Created: 2014-12-05 Last updated: 2015-04-10Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Zackrisson, BjörnKarlsson, Mikael
By organisation
Radiation biologyRadiation Physics
In the same journal
Radiation Research
Cancer and Oncology

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 47 hits
ReferencesLink to record
Permanent link

Direct link