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An in vitro study of the radiobiological effects of flattening filter free radiotherapy treatments.
MedLine Citation:
PMID:  23399781     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Flattening filter free (FFF) linear accelerators allow for an increase in instantaneous dose-rate of the x-ray pulses by a factor of 2-6 over the conventional flattened output. As a result, radiobiological investigations are being carried out to determine the effect of these higher dose-rates on cell response. The studies reported thus far have presented conflicting results, highlighting the need for further investigation. To determine the radiobiological impact of the increased dose-rates from FFF exposures a Varian Truebeam medical linear accelerator was used to irradiate two human cancer cell lines in vitro, DU-145 prostate and H460 non-small cell lung, with both flattened and FFF 6 MV beams. The fluence profile of the FFF beam was modified using a custom-designed Nylon compensator to produce a similar dose profile to the flattened beam (6X) at the cell surface but at a higher instantaneous dose-rate. For both cell lines there appeared to be no significant change in cell survival. Curve fitting coefficients for DU145 cells irradiated with constant average dose-rates were 6X: α = 0.09 ± 0.03, β = 0.03 ± 0.01 and 6FFF: α = 0.14 ± 0.13, β = 0.03 ± 0.02 with a significance of p = 0.75. For H460 cells irradiated with the same instantaneous dose-rate but different average dose-rate the fit coefficients were 6FFF (low dose-rate): α = 0.21 ± 0.11, 0.07 ± 0.02 and 6FFF (high dose-rate): α = 0.21 ± 0.16, 0.07 ± 0.03, with p = 0.79. The results indicate that collective damage behaviour does not occur at the instantaneous dose-rates investigated here and that the use of either modality should result in the same clinical outcome, however this will require further validation in vivo.
Authors:
R B King; W B Hyland; A J Cole; K T Butterworth; S J McMahon; K M Redmond; C Trainer; K M Prise; C K McGarry; A R Hounsell
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-2-11
Journal Detail:
Title:  Physics in medicine and biology     Volume:  58     ISSN:  1361-6560     ISO Abbreviation:  Phys Med Biol     Publication Date:  2013 Feb 
Date Detail:
Created Date:  2013-2-12     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0401220     Medline TA:  Phys Med Biol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  N83-N94     Citation Subset:  -    
Affiliation:
Radiotherapy Physics, Northern Ireland Cancer Centre, Belfast Health and Social Care Trust, BT9 7AB, UK.
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