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Proton-Beam Treatment Planning Techniques
Published in W. P. M. Mayles, A. E. Nahum, J.-C. Rosenwald, Handbook of Radiotherapy Physics, 2021
Francesca Albertini, Alessandra Bolsi, Juliane Daartz
Paganetti et al. (2002) analysed published RBE values for in vitro and in vivo endpoints. The values for cell survival in vitro indicated a substantial spread between the diverse cell lines. The average value at the middle of the SOBP over all dose levels was approximately 1.2 in vitro and approximately 1.1 in vivo. Both in vitro and in vivo data indicated a statistically significant increase in RBE at lower doses per fraction, this increase being much smaller in vivo, and a measurable increase in RBE over the final few millimetres of the SOBP, consistent with the increase in LET as the proton energy decreases. The experimental in vivo data indicate that continued use of a generic RBE value of 1.10 (relative to 60Co γ-rays) is reasonable (Raju 1980). This conclusion has been endorsed in ICRU Report 78 (ICRU 2007), where a constant RBE of 1.10 is recommended everywhere, from the surface to the distal part of the SOBP; this recommendation is also endorsed by the Task Group 256 of the American Association of Physicists in Medicine (AAPM 2019) To distinguish between physical and radiobiological-equivalent dose, ICRU recommends using RBE-weighted dose in clinical practice and to specify that the unit is not physical ‘Gy' by appending ‘RBE'.* Then, a physical absorbed dose of 60 Gy will yield an RBE-weighted dose of 66 GyRBE.
Radiotherapy for Pediatric Central Nervous System Tumors – Techniques and Strategies
Published in David A. Walker, Giorgio Perilongo, Roger E. Taylor, Ian F. Pollack, Brain and Spinal Tumors of Childhood, 2020
The relative biological effectiveness (RBE) is the ratio of the amount of a specified biological effect of one type of ionizing radiation relative to photons given the same amount of absorbed energy. Biological effects of interest to the radiation oncologist include cell killing and normal tissue damage. The first investigation of biological effects of protons was performed by Tobias et al. at the Lawrence Berkeley Laboratory, California. Initial results suggested that the RBE of protons in a mouse model was approximately 1.112 Further in vitro and in vivo studies confirmed protons to have a 10% higher RBE compared with photons, i.e., an RBE of 1.1. Hence, to date, in clinical practice the physical dose delivered by protons is higher by a factor of 1.1 to obtain the biologically effective dose in Gy (measured in cobalt-gray equivalents or CBE). Proton radiation doses are now referred to as Gy (RBE).
Modifications of Cellular Radiation Damage
Published in Kedar N. Prasad, Handbook of RADIOBIOLOGY, 2020
Work already published on the different cell types has established the following general principles regarding RBE: The RBE value for the same effect varies from one type of radiation to another.The RBE value for the same effect and the same type of radiation differs if the radiation is delivered at markedly different energy levels, e.g., fast neutrons vs. slow neutrons.The RBE value changes if the criterion of damage is changed.
LDR-adapted liver-derived cytokines have potential to induce atherosclerosis
Published in International Journal of Radiation Biology, 2023
Eunguk Shin, Dahye Kim, You Yeon Choi, HyeSook Youn, Ki Moon Seong, BuHyun Youn
It should be noted that there is a potential difference in biological effectiveness in our in vivo and in vitro experimental data using different types of radiation, gamma ray and X-ray. RBE (Relative Biological Effectiveness) has been used to describe the effectiveness of different types of radiation on the same specified end-point as cancer development or other health effects. Although gamma ray and x-ray are usually regarded as the same type of radiation, low energy photons with a weighting factor (wR) of 1 for simple comparison to other higher LET radiation, the biological effectiveness of lower-energy of low LET radiation may be more than two times greater than for higher-energy of low-LET (ICRP publication 92 and NCRP Report No.181). Also, RBE generally increases with decreasing dose and dose rate (Barendsen 1992; Sørensen et al. 2021). Conventional 200kV x-rays are considered to be about twice as effective at low doses compared to gamma rays in some in vitro studies, including chromosomal aberrations in human lymphocytes, and killing of mouse oocytes (National Research Council Board on Radiation Effects R 1998). Therefore, our mechanistic results in the irradiated cells should be carefully interpreted for the enhanced understanding of physiological response in the radiation-exposed mice, considering dose rate, fractionation and energy quantity of radiation.
Biological effects of passive scattering and spot scanning proton beams at the distal end of the spread-out Bragg peak in single cells and multicell spheroids
Published in International Journal of Radiation Biology, 2021
Kento Nomura, Hiromitsu Iwata, Toshiyuki Toshito, Chihiro Omachi, Junpei Nagayoshi, Koichiro Nakajima, Hiroyuki Ogino, Yuta Shibamoto
Proton beam therapy is characterized by its distinct dose distribution (Hall and Rouge 2015), and proton beams also exert slightly stronger biological effects than X rays, as implied by a generic relative biological effectiveness (RBE) of 1.1 that is clinically adopted in most institutions. However, RBE varies with physical factors, such as the radiation type, dose, fractionation, beam energy, tissue or cell type, biological endpoint, and position in the spread-out Bragg peak (SOBP) (Vitti and Parsons 2019). RBE was recently shown to increase to 1.35 in the distal end region and 1.7 in the distal fall-off region (Paganetti 2014). These increases in biological effects at the distal end (distal end enhancement) of proton beams have been attracting attention (Guan et al. 2015a; Chaudhary et al. 2016; Iwata et al. 2016; Hojo et al. 2017).
Calculation of microdosimetric spectra for protons using Geant4-DNA and a μ-randomness sampling algorithm for the nanometric structures
Published in International Journal of Radiation Biology, 2021
Mojtaba Mokari, Hossein Moeini, Marzieh Soleimani
Ion beams have the potential to create an absorbed dose profile that could match the tumor volume, reducing the dose delivered to the surrounding healthy tissues. Energy depositions of such ionizing radiations appear to be stochastic both in the magnitude of the deposited energy and in the spatial distribution of the hit points along the particle’s path through the matter. Radiation factors that can affect biological structures include the absorbed dose, the number, distribution, and correlation of hit points, as well as the amount of energy deposited at hit points. As living cells are composed mainly of water molecules, radiation interactions would comprise the physical and physico-chemical ones that could have early biological consequences. Such early damage investigations necessitate veracious modeling of the particle tracks in biological media (Nikjoo et al. 2008). The relative biological effectiveness (RBE) concept, introduced as the ratio of the dose from the reference photon field to the dose of a particle type that causes the same amount of biological damage (ICRP 2003), is usually used to take the biological effects of radiation into account.