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16 th ICNCT June 14-19, 2014 Helsinki, Finland Design and simulation of an optimized photoconverter for e-linac based neutron source for BNCT research.

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Presentation on theme: "16 th ICNCT June 14-19, 2014 Helsinki, Finland Design and simulation of an optimized photoconverter for e-linac based neutron source for BNCT research."— Presentation transcript:

1 16 th ICNCT June 14-19, 2014 Helsinki, Finland Design and simulation of an optimized photoconverter for e-linac based neutron source for BNCT research E.Durisi 1,2, A.Zanini 2, G.Giannini 3,4,G.Vivaldo 1, K.Alikaniotis 1, V.Monti 1, O.Borla 5, F.Bragato 3 1 Dipartimento di Fisica, Università di Torino, Via P. Giuria 1, Torino, Itay 2 Istituto Nazionale di Fisica Nucleare Sez. di Torino, Via P. Giuria 1, Torino, Italy 3 Università di Trieste, Via Valerio 2, Trieste, Italy 4 Istituto Nazionale di Fisica Nucleare Sez. di Trieste, Via Valerio 2, Trieste, Italy 5 Politecnico di Torino, Corso Duca degli Abruzzi 24, Torino, Italy

2 16 th ICNCT June 14-19, 2014 Helsinki, Finland Outline Goal of PSIHO project Summary of the previous results Project of a dedicated facility: linear accelerator and photoconverter Results in terms of free beam parameters and in-phantom dose evaluations Conclusions

3 16 th ICNCT June 14-19, 2014 Helsinki, Finland GOAL of the project Design a neutron source for research in BNCT coupling high energy linear accelerator 18MV - 25MV with a suitable photoconverter PSIHO project is devoted to design and manufacture an in-hospital BNCT facility FUTURE PSIHO: Photoneutron Source In HOspital INFN project (section of Torino and Trieste)

4 16 th ICNCT June 14-19, 2014 Helsinki, Finland Photoneutron production in LINAC Electrons ~20 MeV Linac Target X-ray emission by Bremsstrahlung Neutrons are produced by ( γ,n) reaction (photodisintegration) mainly on high Z material when E  > threshold energy reaction (W: 7.42MeV, Fe: 10.9MeV, Pb: 7.41 MeV) Varian 2300 CD 18MV MCNP Neutron plane Field 10x10 cm 2 Mean neutron energy 700keV

5 16 th ICNCT June 14-19, 2014 Helsinki, Finland Photoconverter design The study of the photoconverter materials and geometries has been carried in order to: increase the photoneutron production; maximize the therapeutic neutron component of the beam (E < 10 keV); minimize the fast neutron component and  undesired dose. The main components of the photonconverter are: Final configuration Core Increase ( ,n) production (High Z elements: Pb, W) Moderator: Slow down neutron energy up to thermal/epithermal range, minimizing fast neutron component (Graphite, D 2 O, Polyethylene) Gamma shielding minimize gamma (Pb e Bi) Lead Graphite 60 cm Polyethylene, B 4 C, Lead Neutron reflector increase neutron flux (Graphite, Pb)

6 16 th ICNCT June 14-19, 2014 Helsinki, Finland PhoNeS “Bianco”prototype First in-hospital neutron source for BNCT trials Phones+Elekta precise 25MV  th = cm -2 s -1 ± 20% Summary of the previous results Transportable PhoNeS prototype closed cavity configuration Cavity: 20 x 20 x 5 cm 3 Thermal neutron field of suitable intensity and energy spectral distribution for BNCT research and experiments on cells and biological samples Irradiation time ~ 3hrs  ~ cm -2 GRAPHITE LEAD D2OD2O POLYETHYLENE Thermal neutrons (85%) (1.04±0.02) 10 7 cm -2 s -1 Epithermal neutrons (11%) (1.39±0.07)10 6 cm -2 s -1 Fast neutrons (4%) (4.8±0.3) 10 5 cm -2 s -1

7 16 th ICNCT June 14-19, 2014 Helsinki, Finland INFN Project of a dedicated facility for BNCT reasearch -Installation of LINAC Elekta Precise 18 MV (no longer in use in radiotherapy department) in the Physics Department of the University of Torino -modification of LINAC accelerator -construction of an optimized photoconverter -test

8 16 th ICNCT June 14-19, 2014 Helsinki, Finland A dedicated facility for BNCT reasearch Monte Carlo approach to optimize the photoconverter geometry - MCNP4B─GN (NEA-1733) - MCNP 5 - GEANT 4 Investigate possible modification of: - linac working parameters - linac accelerator head components

9 16 th ICNCT June 14-19, 2014 Helsinki, Finland Dedicated linear accelerator for BNCT research Elekta Precise 18MV Photon mode25 MV18 MV15 MV10 MV6 MV18 MV modified Dose rate (MU/min)400 Electron energy (MeV) T (  s) I (mA) (Hz) Power (W) K (x10 14 e - s -1 ) Elekta manufacturer provided Elekta Precise 18 MV modified: I = 50 mA;  = 200 Hz; T = 2.8  s Electrons rate = 1/1.602x x I x x T = e- s -1  Conversion factor cm 2 /e - cm 2 /s depends on LINAC duty cycle  MCNP : Average neutron fluence rate cross a surface (cm 2 /e - )

10 16 th ICNCT June 14-19, 2014 Helsinki, Finland Effect of the flattening filter on the photon beam inetensity Modification of Elekta Precise 18MV with FF Total fluence rate (3.727±0.005)10 11 cm -2 s -1 without FF Total fluence rate (8.967 ± 0.015)10 11 cm -2 s -1 Photon fluence rate increases ~2 times (from cm -2 s -1 to cm -2 s -1 )

11 16 th ICNCT June 14-19, 2014 Helsinki, Finland New PhoNes - open cavity configuration Lead Polyethylene Heavy water Graphyte Borate polyethylene Fluence rateWith FFWithout FF cm -2 s -1 % Hyperthermal1.51E+07±0.02E E+07±0.02E+0775 Fast4.83E+06±0.07E E+06±0.11E+0625

12 16 th ICNCT June 14-19, 2014 Helsinki, Finland Comparison MCNP5 - MCNP4B_GN MCNP4B-GN photoneutron production on high Z elements is implemented: - ( ,n) and ( ,2n) are included - evaporative and direct models are used. photoneutron production on low Z elements is implemented: - only ( ,n) reaction and direct model. MCNP5 cross section - endfbVII -mcplib04 -el03 MCNP 5 Photoneutron production on high and few low Z elements is implemented. - evaporative (Giant Dipole Resonance) and direct models (Quasi Deuteron) are used MCNP-GN cross section - endfbVI -mcplib02 -el1

13 16 th ICNCT June 14-19, 2014 Helsinki, Finland New PhoNes - closed cavity configuration Lead Polyethylene Heavy water Graphyte Borate polyethylene Fluence rateWith FFWithout FF cm -2 s -1 % Hyperthermal3.14E+07±0.03E E+07±0.05E+0781 Fast7.10E+06±0.11E E+07±0.02E+0719

14 16 th ICNCT June 14-19, 2014 Helsinki, Finland IAEA PhoNeS Bianco Without FF New PhoNes Closed cavity With FF New PhoNes Closed cavity Without FF  th+epith cm -2 s -1 > (5,17±0.05)10 7 (3.14±0.03) 10 7 (5.86±0.05)10 7 D  /  th+epi Gy cm 2 < (1.35±0.02) (3.41±0.08) (5.07±0.09) D f /  th+epi Gy cm 2 < (1.00±0.04) (2.99±0.11) (3.2±0.1) Calculated free beam parameters

15 16 th ICNCT June 14-19, 2014 Helsinki, Finland In phantom dose evaluations The anthropomorphic phantom “Jimmy” was designed and realized by INFN Sez. Torino, in collaboration with JRC Varese. Materials: polyethylene and plexiglas, with inserted human bone in correspondence of column. Cavities are placed in correspondence of critical organs and are suitable to allocate passive dosemeters such as bubble detectors, TLDs... Cross section of phantom realized with MCNP Organs composition from ICRU report 46 (International Commission on Radiation Measurements and Units, 1992) x y z

16 16 th ICNCT June 14-19, 2014 Helsinki, Finland In phantom dose evaluations The phantom is placed in front of the cavity. A left lung treatment is investigated. 3 irradiations are considered (A-P, P-A, LAT). The biological dose is calculated in all the organs. LAT P-A RBE  (w  ) RBE n (wn) 10 B (ppm) CBE (w B ) Left lung tumour 13,2763,8 Left lung healhty 13,2191,3 Other organs 13,2191,3 Biological dose = D W = w  D  + w n (D H + D N ) + w B D B

17 16 th ICNCT June 14-19, 2014 Helsinki, Finland In phantom dose evaluations LAT Treatment planning for left lung tumour with crossed photon beams. ELEKTA 6 MV (0°- 180°-270°)

18 16 th ICNCT June 14-19, 2014 Helsinki, Finland In phantom dose evaluations LAT

19 16 th ICNCT June 14-19, 2014 Helsinki, Finland The study of a new facility based on a linear accelerator devoted to BNCT research and a new photoconverter was carried out. A dedicated facility allows to modify LINAC working parameters and the accelerator head components in order to increase the photon production. Simulations demonstrated that without flattening filter the photon fluence rate useful for ( ,n) reaction increases of a factor 2. Different photoconverters were simulated. The configuration with closed cavity, suitable for the irradiation of biological samples, provides a neutron fluence rate (E < 10 keV) of (5.86±0.05)10 7 cm -2 s -1 The irradiation time is therefore reduced to ~ 30 min to get neutrons cm -2. The gamma dose is still high and needs to be further reduced as well as the fast neutron one. A preliminary evaluation of biological dose distribution in phantom was realized simulating a treatment to left lung with 3 crossed beams. Conclusions

20 16 th ICNCT June 14-19, 2014 Helsinki, Finland 20 Università degli Studi di Torino Università degli Studi di Trieste Università dell’ Insubria di Como Università degli Studi di Pavia ASO Ordine Mauriziano (Torino) AOU San Luigi – Orbassano (Torino) AOU San Giovanni Battista (Torino) ASO Sant’Anna (Como) Ospedale Maggiore (Trieste) ST. JOHANNS HOSPITAL Salisburgo (AUSTRIA) GIO’ MARCO s.p.a. MOGLIANO VENETO (Treviso) The project was financially supported by: Italian National Institute of Nuclear Physics Italian Ministery of Industry, Research and University CRT fundation Acknowledgments

21 16 th ICNCT June 14-19, 2014 Helsinki, Finland LAT Thank you!


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