scholarly journals Neutron dose and its measurement in proton therapy—current State of Knowledge

2020 ◽  
Vol 93 (1107) ◽  
pp. 20190412 ◽  
Author(s):  
Roger Antoine Hälg ◽  
Uwe Schneider

Proton therapy has shown dosimetric advantages over conventional radiation therapy using photons. Although the integral dose for patients treated with proton therapy is low, concerns were raised about late effects like secondary cancer caused by dose depositions far away from the treated area. This is especially true for neutrons and therefore the stray dose contribution from neutrons in proton therapy is still being investigated. The higher biological effectiveness of neutrons compared to photons is the main cause of these concerns. The gold-standard in neutron dosimetry is measurements, but performing neutron measurements is challenging. Different approaches have been taken to overcome these difficulties, for instance with newly developed neutron detectors. Monte Carlo simulations is another common technique to assess the dose from secondary neutrons. Measurements and simulations are used to develop analytical models for fast neutron dose estimations. This article tries to summarize the developments in the different aspects of neutron dose in proton therapy since 2017. In general, low neutron doses have been reported, especially in active proton therapy. Although the published biological effectiveness of neutrons relative to photons regarding cancer induction is higher, it is unlikely that the neutron dose has a large impact on the second cancer risk of proton therapy patients.

2016 ◽  
Vol 17 (5) ◽  
pp. 366-376 ◽  
Author(s):  
Xin Wang ◽  
Falk Poenisch ◽  
Narayan Sahoo ◽  
Ronald X. Zhu ◽  
MingFwu Lii ◽  
...  

2012 ◽  
Vol 8 (S295) ◽  
pp. 191-199
Author(s):  
Carlton M. Baugh

AbstractMassive galaxies with old stellar populations have been put forwards as a challenge to models in which cosmic structures grow hierarchically through gravitational instability. I will explain how the growth of massive galaxies is helped by features of hierarchical models. I give a brief outline of how the galaxy formation process is modelled in hierarchical cosmologies using semi-analytical models, and illustrate how these models can be refined as our understanding of processes such as star formation improves. I then present a brief survey of the current state of play in the modelling of massive galaxies and list some outstanding challenges.


2019 ◽  
Vol Volume 12 ◽  
pp. 8033-8046 ◽  
Author(s):  
Umberto Ricardi ◽  
Maja V Maraldo ◽  
Mario Levis ◽  
Rahul R Parikh

2020 ◽  
Vol 189 (2) ◽  
pp. 190-197 ◽  
Author(s):  
Serdar Charyyev ◽  
C-K Chris Wang

Abstract New technique is trending in spatially fractionated radiotherapy with protons to utilize the spot scanning together with a physical collimator to obtain minibeams. The primary goal of this study is to quantify ambient neutron dose equivalent (${H}^{\ast }(10)$) due to the secondary neutrons when physical collimator is used to achieve desired minibeams. The ${H}^{\ast }(10)$ per treatment proton dose (D) was assessed using Monte Carlo code TOPAS and measured using WENDI-II detector at different angles (135, 180, 225 and 270 degrees) and distances (11 cm, 58 and 105 cm) from the phantom for two cases: with and without physical collimation. Without collimation $\frac{H^{\ast }(10)}{D}$ varied from 0.0013 to 0.242 mSv/Gy. With collimation $\frac{H^{\ast }(10)}{D}$ varied from 0.017 to 3.23 mSv/Gy. Results show that the secondary neutron dose will increase tenfold when the physical collimator is used. Regardless, it will be low and comparable to the neutron dose produced by conventional passive-scattered proton beams.


2020 ◽  
Author(s):  
Christian Hahn ◽  
Jan Eulitz ◽  
Nils Peters ◽  
Patrick Wohlfahrt ◽  
Wolfgang Enghardt ◽  
...  

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