An international journal published by K. N. Toosi University of Technology

Document Type : Research Article


1 Department of Medical Radiation Engineering‎, ‎Science and Research Branch‎, ‎Islamic Azad University‎, ‎Tehran‎, ‎Iran

2 Iran University of Medical Sciences‎, ‎Medical Physics Department‎, ‎Tehran‎, ‎Iran

3 Radiation Application Research School‎, ‎Nuclear Science & Technology Research Institute‎, ‎PO Box 31485-498‎, ‎Karaj‎, ‎Iran


‎Collision of protons with background gas and beamline wall in proton therapy causes the creation of secondary particles‎, ‎e.g. neutrons‎, ‎which results in more difficulties in curing the tumors‎. ‎In the present simulation-based study‎, ‎the optimum diameter of proton beamline was determined to minimize the production of secondary particles in the presence of electric field with the magnitude of 50 kV/m‎, ‎perpendicular equal magnetic fields of 0.7 T‎, ‎and background gas of argon under Bounce boundary conditions via finite element method‎. ‎The results showed that the optimum diameter of the beamline for minimization of the secondary particles in the spot scanning proton therapy in the aforementioned conditions was 7 mm‎. ‎Also‎, ‎the values of drift velocities of protons were plotted in different time steps of 10 ns to 50 ns for the optimized size of the beamline‎. ‎Due to few interactions of forwarding particles with background gas‎, ‎the results showed that the forwarding particles in the propagation direction have greater velocities than those of rear particles‎. ‎The results can be used in spot scanning proton therapy for curing the localized cancers‎.


  • Spot scanning proton therapy was simulated via the finite element method‎.
  • ‎The optimum diameter of proton beamline was determined to minimize the production of secondary particles‎.
  • The forward particles exhibited greater velocities than those of rear particles‎.


Chang, J. Y., Jabbour, S. K., De Ruysscher, D., et al. (2016). Consensus statement on proton therapy in early-stage and locally advanced non–small cell lung cancer. International Journal of Radiation Oncology* Biology* Physics, 95(1):505–516.
COMSOL (1994). Guide, comsol multiphysics users. Inc. 2006.-708 p.
COMSOL (2013). Comsol multiphysics user guide (version 4.3 a). COMSOL, AB, pages 39–40.
Deasy, J. (1994). ICRU Report 49, stopping powers and ranges for protons and alpha particles. Medical Physics, 21(5):709–710.
Elnahal, S. M., Kerstiens, J., Helsper, R. S., et al. (2013). Proton beam therapy and accountable care: the challenges ahead. International Journal of Radiation Oncology* Biology* Physics, 85(4):e165–e172.
Gottschalk, B. (2006). Neutron dose in scattered and scanned proton beams: In regard to Eric J. Hall (Int J Radiat Oncol Biol Phys 2006; 65: 1–7). International Journal of Radiation Oncology* Biology* Physics, 66(5):1594.
Grevillot, L., Bertrand, D., Dessy, F., et al. (2011). A Monte Carlo pencil beam scanning model for proton treatment plan simulation using GATE/GEANT4. Physics in Medicine and Biology, 56(16):5203.
Haberer, T., Becher, W., Schardt, D., et al. (1993). Magnetic scanning system for heavy ion therapy. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 330(1-2):296–305.
Hall, E. J. (2006). Intensity-modulated radiation therapy, protons, and the risk of second cancers. International Journal of Radiation Oncology* Biology* Physics, 65(1):1–7.
Ho, E. S., Barrett, S. A., and Mullaney, L. M. (2017). A review of dosimetric and toxicity modeling of proton versus photon craniospinal irradiation for pediatrics medulloblastoma. Acta Oncologica, 56(8):1031–1042.
Hyer, D. E., Hill, P. M.,Wang, D., et al. (2014). Effects of spot size and spot spacing on lateral penumbra reduction when using a dynamic collimation system for spot scanning proton therapy. Physics in Medicine and Biology, 59(22):N187.
Jansen, E. P., Dewit, L. G., van Herk, M., et al. (2000). Target volumes in radiotherapy for high-grade malignant glioma of the brain. Radiotherapy and Oncology, 56(2):151–156.
Jia, S. B., Hadizadeh, M. H., Mowlavi, A. A., et al. (2014). Evaluation of energy deposition and secondary particle production in proton therapy of brain using a slab head phantom. Reports of Practical Oncology and Radiotherapy, 19(6):376–384.
Jiang, H., Wang, B., Xu, X. G., et al. (2005). Simulation of organ-specific patient effective dose due to secondary neutrons in proton radiation treatment. Physics in Medicine and Biology, 50(18):4337.
Kraft, G. (2000). Tumor therapy with heavy charged particles. Progress in Particle and Nuclear Physics, 45:S473–S544.
Lin, R., Hug, E. B., Schaefer, R. A., et al. (2000). Conformal proton radiation therapy of the posterior fossa: a study comparing protons with three-dimensional planned photons in limiting dose to auditory structures. International Journal of Radiation Oncology* Biology* Physics, 48(4):1219–1226.
Lomax, A. J., B¨ohringer, T., Bolsi, A., et al. (2004). Treatment planning and verification of proton therapy using spot scanning: Initial experiences. Medical Physics, 31(11):3150–3157.
Lomax, A. J., Bortfeld, T., Goitein, G., et al. (1999). A treatment planning inter-comparison of proton and intensity modulated photon radiotherapy. Radiotherapy and Oncology, 51(3):257–271.
Malekie, S. and Ziaie, F. (2017). A two-dimensional simulation to predict the electrical behavior of carbon nanotube/polymer composites. Journal of Polymer Engineering, 37(2):205–210.
McDonald, M. W. and Fitzek, M. M. (2010). Proton therapy. Current problems in cancer, 34(4):257.
Newhauser, W. D. and Zhang, R. (2015). The physics of proton therapy. Physics in Medicine and Biology, 60(8):R155.
Owen, H., Holder, D., Alonso, J., et al. (2014). Technologies for delivery of proton and ion beams for radiotherapy. International Journal of Modern Physics A, 29(14):1441002.
Pedroni, E., Bacher, R., Blattmann, H., et al. (1995). The 200-MeV proton therapy project at the Paul Scherrer Institute: Conceptual design and practical realization. Medical Physics, 22(1):37–53.
Poenisch, F., Gillin, M., Sahoo, N., et al. (2016). SU-F-T-165: Daily QA analysis for spot scanning beamline. Medical Physics, 43(6Part15):3499–3500.
Reddy, J. N. (2005). An introduction to the finite element method. 3rd Edition, volume 2. McGraw-Hill New York.
Ricardi, U., Dabaja, B., and Hodgson, D. (2017). Proton therapy in mediastinal Hodgkin lymphoma: moving from dosimetric prediction to clinical evidence.
Schlegel, W., Bortfeld, T., Grosu, A.-L., et al. (2008). New Technologies in Radiation Oncology. Journal of Nuclear Medicine, 49(4):683–684.
Schneider, U., Agosteo, S., Pedroni, E., et al. (2002). Secondary neutron dose during proton therapy using spot scanning. International Journal of Radiation Oncology*Biology*Physics, 53(1):244–251.
Smith, B., Gelover, E., Moignier, A., et al. (2016). A treatment plan comparison between dynamic collimation and a fixed aperture during spot scanning proton therapy for brain treatment. Medical Physics, 43(8Part1):4693–4699.
Søbstad, J. M. (2017). Monte Carlo based comparison of constant vs. variable RBE for proton therapy patients. Master’s thesis, The University of Bergen.
Timmermann, B., Schuck, A., Niggli, F., et al. (2007). Spotscanning proton therapy for malignant soft tissue tumors in childhood: First experiences at the Paul Scherrer Institute. International Journal of Radiation Oncology* Biology*Physics, 67(2):497–504.
van de Water, T. A., Lomax, A. J., Bijl, H. P., et al. (2012). Using a reduced spot size for intensity-modulated proton therapy potentially improves salivary gland-sparing in oropharyngeal cancer. International Journal of Radiation Oncology*Biology* Physics, 82(2):e313–e319.
Weber, D. C., Rutz, H. P., Pedroni, E. S., et al. (2005). Results of spot-scanning proton radiation therapy for chordoma and chondrosarcoma of the skull base: the Paul Scherrer Institut experience. International Journal of Radiation Oncology*Biology* Physics, 63(2):401–409.
Yao, W., Merchant, T. E., and Farr, J. B. (2016). A correction scheme for a simplified analytical random walk model algorithm of proton dose calculation in distal Bragg peak regions. Physics in Medicine and Biology, 61(20):7397.