Relative biological effectiveness in a proton spread-out Bragg peak formed by pencil beam scanning mode.
In recent years, there is an increased interest in using scanning modes in proton therapy, due to the more conformal dose distributions, thanks to the spot-weighted dose delivery. The dose rate in each spot is however much higher than the dose rate when using passive irradiation modes, which could affect the cell response. The purpose of this work was to investigate how the relative biological effectiveness changes along the spread-out Bragg peak created by protons delivered by the pencil beam scanning mode. Cell survival and micronuclei formation were investigated in four positions along the spread-out Bragg peak for various doses. Monte Carlo simulations were used to estimate the dose-averaged linear energy transfer values in the irradiation positions. The cell survival was found to decrease the deeper the sample was placed in the spread-out Bragg peak, which corresponds to the higher linear energy transfer values found using Monte Carlo simulations. The micronuclei frequencies indicate more complex cell injuries at that distal position compared to the proximal part of the spread-out Bragg peak. The relative biological effectiveness determined in this study varies significantly and systematically from 1.1, which is recommended value by the International Commission on Radiation Units, in all the studied positions. In the distal position of spread-out Bragg peak the relative biological effectiveness values were found to be 2.05 ± 0.44, 1.85 ± 0.42, 1.53 ± 0.38 for survival levels 90, 50 and 10%, respectively.
Nuclear Physics Institute of the Czech Academy of Sciences, Řež 130, 25068, Řež, Czech Republic. anna.michaelidesova@odz.ujf.cas.cz.|Proton Therapy Center Czech, Budínova 2437/1a, 18000, Prague, Czech Republic. anna.michaelidesova@odz.ujf.cas.cz.|Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University, Břehová 7, 11519, Prague, Czech Republic. anna.michaelidesova@odz.ujf.cas.cz.
Anna
http://orcid.org/0000-0002-9478-869X
A
Michaelidesová
Nuclear Physics Institute of the Czech Academy of Sciences, Řež 130, 25068, Řež, Czech Republic.
Jana
J
Vachelová
Atominstitut, Technische Universität Wien, Stadionallee 2, 1020, Vienna, Austria.
Monika
M
Puchalska
Nuclear Physics Institute of the Czech Academy of Sciences, Řež 130, 25068, Řež, Czech Republic.
Kateřina Pachnerová
KP
Brabcová
Proton Therapy Center Czech, Budínova 2437/1a, 18000, Prague, Czech Republic.
Vladimír
V
Vondráček
Atominstitut, Technische Universität Wien, Stadionallee 2, 1020, Vienna, Austria.|EBG, MedAustron, Marie-Curie-Straße 5, 2700, Wiener Neustadt, Vienna, Austria.
Lembit
L
Sihver
Nuclear Physics Institute of the Czech Academy of Sciences, Řež 130, 25068, Řež, Czech Republic.|Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University, Břehová 7, 11519, Prague, Czech Republic.
Marie
M
Davídková
D002470:Cell Survival / Q000528:radiation effects; D003198:Computer Simulation; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D007231:Infant, Newborn; D018499:Linear Energy Transfer; D015162:Micronucleus Tests; D011522:Protons; D011874:Radiometry; D012062:Relative Biological Effectiveness
D011522:Protons
Clonogennic assay; Micronuclei assay; Monte Carlo simulations; Proton therapy; Relative biological effectiveness; Scanning beam