Journal List > Prog Med Phys > v.27(3) > 1098548

TOOLS
Lee, Lee, Chung, Han, Chung, and Kim: Secondary Neutron Dose Measurement for Proton Line Scanning Therapy
Original Article

Progress in Medical Physics 2016;27(3):162-168.

Published online: 19 September 2016

DOI: https://doi.org/10.14316/pmp.2016.27.3.162

Secondary Neutron Dose Measurement for Proton Line Scanning Therapy

Chaeyeong Lee∗, Sangmin Lee§, Kwangzoo Chung‡, Youngyih Han‡, Yong Hyun Chung∗, Jin Sung Kim†,

∗Department of Radiological Science, Yonsei University, Wonju, Korea

†Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Korea

‡Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Korea

§Program in Biomedical Radiation Sciences, Department of Transdisciplinary Studies, Graduate School of Convergence Science and Technology, Seoul National University, Seoul, Korea

Correspondence: Jin Sung Kim (jinsung@yuhs.ac) Tel: 82-2-2228-8110, Fax: 82-2-2227-7823

Received 20 September 201623 September 2016       Accepted 24 September 2016

Copyright © 2016 Korean Society of Medical Physics

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Proton therapy is increasingly being actively used in the treatment of cancer. In contrast to photons, protons have the potential advantage of delivering higher doses to the cancerous tissue and lower doses to the surrounding normal tissue. However, a range shifter is needed to degrade the beam energy in order to apply the pencil beam scanning technique to tumors located close to the minimum range. The secondary neutrons are produced in the beam path including within the patient's body as a result of nuclear interactions. Therefore, unintended side effects may possibly occur. The research related to the secondary neutrons generated during proton therapy has been presented in a variety of studies worldwide, since 2007. In this study, we measured the magnitude of the secondary neutron dose depending on the location of the detector and the use of a range shifter at the beam nozzle of the proton scanning mode, which was recently installed. In addition, the production of secondary neutrons was measured and estimated as a function of the distance between the isocenter and detector. The neutron dose was measured using WENDI-II (Wide Energy Neutron Detection Instruments) and a Plastic Water phantom; a Zebra dosimeter and 4-cm-thick range shifter were also employed as a phantom. In conclusion, we need to consider the secondary neutron dose at proton scanning facilities to employ the range shifter reasonably and effectively.

Keywords: Proton therapy, Range shifter, Secondary neutron

REFERENCES

1.Miller DW. A review of proton beam radiation therapy. Medical physics. 22:1943. 1995.
crossref
2.Olsen DR, et al. Proton therapy –A systematic review of clinical effectiveness. Radiother Oncol 83: 123. 2007.
3.Particle Therapy Co-Operative Group. Particle therapy facilities under construction [Internet]. [place un known]: Particle Therapy Co-Operative Group; Available from:. http://www.ptcog.ch/index.php/facilities-under-construction.
4.Shin JS, et al. Analysis of changes in dose distribution due to respiration during IMRT. Radiat Oncol J 29: 206. 2011.
crossref
5.Schneider U., Lomax A., Lombriser N. Comparative risk assessment of secondary cancer incidence after treatment of Hodgkin's disease with photon and proton radiation. Radiat Res. 154(4):): 382–388. 2000.
crossref
6.Paganetti H. Nuclear interactions in proton therapy: Dose and relative biological effect distributions originating from primary and secondary particles. Phys Med Biol. 47:747–764. 2002.
crossref
7.Zacharatou JC., Paganetti H. Risk of developing second cancer from neutron dose in proton therapy as function of field characteristics: organ and patient age. Int J Radiat Oncol Biol Phys. 82:228–35. 2008.
8.Kim JS, et al. Feasibility study of neutron dose for real-time image-guided proton therapy: a Monte Carlo study. JKPS. 67(1):142–146. 2015.
9.Yonai S, et al. Measurement of neutron ambient dose equivalent in passive carbon-ion and proton radiotherapies. Med Phys. 35:4782–4792. 2008.
crossref
10.Hall EJ. Intensity modulated radiation therapy, protons, and the risk of second cancers Int J Radiat Oncol Biol Phys. 65:1–7. 2006.
11.Chung KZ, et al. The first private-hospital based proton therapy center in Korea; Status of the Proton Therapy Center at Samsung Medical Center. Radiat Oncol J. 33(4):1–7. 2015. . DOI: doi: 10.3857/roj.2015.33.4.337.
crossref
12.https://www.thermofisher.com/order/catalog/product/FHT762WENDI2.
13.ICRP. 1977. Recommendations of the ICRP. ICRP Publication 26. Ann. ICRP. 1(3):

Fig. 1
Range shifter.
pmp-27-162f1.tif
Fig. 2
WENDI-II detector.
pmp-27-162f2.tif
Fig. 3
Schematic of first experiment.
pmp-27-162f3.tif
Fig. 4
Schematic of second experiment.
pmp-27-162f4.tif
Fig. 5
Two-dimensional dosage distribution within phantom irradiated by four proton scanning methods to assess neutron dose of range shifter.
pmp-27-162f5.tif
Fig. 6
Measurement of secondary neutron using WENDI-II. Upper left and right: neutron emission measurements taken with a range shifter; lower left: emission measurement taken without a range shifter; lower right: emission measurements taken from a phantom.
pmp-27-162f6.tif
Fig. 7
Secondary neutron dose on the radial axis from isocenter.
pmp-27-162f7.tif
Fig. 8
Secondary neutron dose on the beam axis from the isocenter.
pmp-27-162f8.tif
Fig. 9
Value of secondary neutron/Exp_1.
pmp-27-162f9.tif
Fig. 10.
Value of secondary neutron/Exp_2.
pmp-27-162f10.tif
Table 1.
WENDI-II technical specification.
Measuring range 0.01 μSv/h to 100 mSv/h Cf-252 Gamma-sensitivity 1 to 5 μSv/h at 100 mSv/h, 662 keV
Sensitivity 0.84 cps/(μSv/h) Cf-252 Ambient temperature −30 to ＋50oC
Energy range 25 meV to 5 GeV according to ICRP 74 (1996) Humidity Up to 90% non-condensing
Angular dependence ±20% all directions Atmospheric pressure 500 to 1,500 hPa
Linearity ±20% Height 320 mm (12.6”)
Diameter 230 mm (9”) Weighting range 13.5 kg (29.8 lb)
Table 2.
Secondary neutron dose of a plastic water phantom at varying distance.
Energy (MeV) 230 MeV            
Field size 10×10×10 cm3            
Gantry angle 270o            
Phantom Plastic Water phantom (30×30×24.7 cm3)        
Position A B C D E F G
Detected WENDI-II position Radial: Radial: Radial: Trans axial: Trans axial: Trans axial: Trans axial:
−50 cm −75 cm −100 cm −40 cm −60 cm −90 cm −110 cm
Neutron dose (mSv/Gy) 0.219 0.110 0.076 0.269 0.150 0.094 0.069
Table 3.
Secondary neutron dose of dedicated scanning nozzle using range shifter position 1.
Plan no. 1 2 3 4  
Proton range (cm) 8.5 19.5 21 30  
SOBP (cm) 3 5 8 8  
Detected WENDI-II position   BAX: 100 cm    
Neutron dose (mSv/Gy) 0.033 0.017 0.161 0.377 With 4 cm range shifter
Neutron dose (mSv/Gy) 0.009 0.088 0.219 0.461 Without 4 cm range shifter
Table 4.
Secondary neutron dose of dedicated scanning nozzle using range shifter position 2.
Plan no. 1 2 3 4
Proton range (cm) 8.5 19.5 21 30
SOBP (cm) 3 5 8 8
Detected WENDI-II position   BAX: −25 cm  
    Radial: 30 cm  
Neutron dose (mSv/Gy) 0.028 0.085 0.324 0.456 With 4 cm range shifter
Neutron dose (mSv/Gy) 0.024 0.061 0.269 0.370 Without 4 cm range shifter
TOOLS
Similar articles