SU-E-T-495: Influence of Reduced Target-To-Nozzle Distance On Secondary Neutron Dose Equivalent in Proton and Carbon Ion Radiotherapy

2015 ◽  
Vol 42 (6Part20) ◽  
pp. 3448-3448
Author(s):  
Y Sheng ◽  
K Shahnazi ◽  
W Wang ◽  
M Moyers ◽  
Y Deng ◽  
...  
Keyword(s):  
Neutron Dose ◽  
Carbon Ion Radiotherapy ◽  
Dose Equivalent ◽  
Secondary Neutron ◽  
Carbon Ion ◽  
Neutron Dose Equivalent

ASSESSMENT OF AMBIENT NEUTRON DOSE EQUIVALENT IN SPATIALLY FRACTIONATED RADIOTHERAPY WITH PROTONS USING PHYSICAL COLLIMATORS

2020 ◽  
Vol 189 (2) ◽  
pp. 190-197 ◽  
Author(s):  
Serdar Charyyev ◽  
C-K Chris Wang
Keyword(s):  
Monte Carlo ◽  
Neutron Dose ◽  
Monte Carlo Code ◽  
Dose Equivalent ◽  
Secondary Neutron ◽  
Fractionated Radiotherapy ◽  
Spot Scanning ◽  
Neutron Dose Equivalent ◽  
Secondary Neutrons ◽  
Proton Dose

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.

Neutron dose evaluation of Elekta Linac at two energies (10 & 18 MV) by MCNP code and comparison with experimental measurements

2014 ◽  
Vol 6 (1) ◽  
pp. 1006-1015
Author(s):  
Negin Shagholi ◽  
Hassan Ali ◽  
Mahdi Sadeghi ◽  
Arjang Shahvar ◽  
Hoda Darestani ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Measurement Data ◽  
Calculated Data ◽  
High Energy ◽  
Neutron Dose ◽  
Dose Assessment ◽  
Photon Flux ◽  
Dose Equivalent ◽  
Monte Carlo Techniques ◽  
Neutron Dose Equivalent

Medical linear accelerators, besides the clinically high energy electron and photon beams, produce other secondary particles such as neutrons which escalate the delivered dose. In this study the neutron dose at 10 and 18MV Elekta linac was obtained by using TLD600 and TLD700 as well as Monte Carlo simulation. For neutron dose assessment in 2020 cm2 field, TLDs were calibrated at first. Gamma calibration was performed with 10 and 18 MV linac and neutron calibration was done with 241Am-Be neutron source. For simulation, MCNPX code was used then calculated neutron dose equivalent was compared with measurement data. Neutron dose equivalent at 18 MV was measured by using TLDs on the phantom surface and depths of 1, 2, 3.3, 4, 5 and 6 cm. Neutron dose at depths of less than 3.3cm was zero and maximized at the depth of 4 cm (44.39 mSvGy-1), whereas calculation resulted  in the maximum of 2.32 mSvGy-1 at the same depth. Neutron dose at 10 MV was measured by using TLDs on the phantom surface and depths of 1, 2, 2.5, 3.3, 4 and 5 cm. No photoneutron dose was observed at depths of less than 3.3cm and the maximum was at 4cm equal to 5.44mSvGy-1, however, the calculated data showed the maximum of 0.077mSvGy-1 at the same depth. The comparison between measured photo neutron dose and calculated data along the beam axis in different depths, shows that the measurement data were much more than the calculated data, so it seems that TLD600 and TLD700 pairs are not suitable dosimeters for neutron dosimetry in linac central axis due to high photon flux, whereas MCNPX Monte Carlo techniques still remain a valuable tool for photonuclear dose studies.

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