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Neutron source monitor

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					Study of a DD compact neutron generator
                for BNCT


                    Elisabetta Durisi
                      Lorenzo Visca




     durisi@to.infn.it,   visca@to.infn.it   - April 18th, 2005   1
                                 Collaborations
The research activity is performed in the mainframe of:
  "Terapie oncologiche innovative basate sulla cattura di neutroni (NCT) con
 nuove tipologie di sorgenti di neutroni e di molecole-target a base di Boro e
                                  Gadolinio"
supported by Azienda Ospedaliera San Giovanni Battista A.S. (dipartimento
Oncologia) and included in the Oncology Program financed by Compagnia di
San Paolo.

• Lawrence Berkeley National Laboratory (Accelrator & Fusion division)
• Experimental Physics Department, University of Turin
• S. Giovanni Battista Hospital Torino, Italy – Molinette Hospital Torino, Italy
• INFN section of Turin, Italy
• ENEA (Frascati - Bologna)
• EUROSEA, Turin
• Nuclear Energy Department, Polytechnic of Milan
• Chemistry Department, University of Turin


                durisi@to.infn.it,   visca@to.infn.it    - April 18th, 2005        2
                           Neutron Sources
                                                            Within patient’s body
            fast                   epithermal                        slow
          neutrons                  neutrons                       neutrons
                                                                               Cell-killing
Neutron              Moderator                         Tissue                 10B-Capture
sources               Material                       (moderator)               in Tumour

   Epithermal neutron (0.4 eV - 10 keV) beams are available
    from existing nuclear reactors.
    Charged-particle  accelerators,    compact        neutron
    generators and hospital radiotherapy facilities for BNCT
    (PHONES, INFN project) are now under development.

   Epithermal neutrons lose energy in the patient body and
    become capturable slow neutrons while proceeding to the
    tumour.

             durisi@to.infn.it,   visca@to.infn.it      - April 18th, 2005                    3
             DD compact neutron generator developed
             by LBNL - accelerator and fusion division
                      45 cm                                           • A 13.56 MHz radio
                                             High Voltage Shield
                                                                        frequency (RF) discharge
                                              Target Water              is used to produce
                                              Manifold
                                                                        deuterium ions.
                                              Al2O3 High
                                              Voltage Insulator       • The ion beam is
                                              Target Cylinder
                                                                        accelerated to energy of
gas in
                                               Secondary Electron
                                                                        120 kV.
                                               Filter Electrode
                                                                      • The beam impinges on a
     60 cm




                                         Ion Source
                                                      RF-Induction      titanium coated
                                               RF-Induction Antenna
                                                      Antenna           aluminum target where
Vacuum                                                                  neutrons are generated
Chamber
                                                                        through D-D fusion
                                                                        reaction:
 RF-Antenna Guide                              Vacuum Pump
                                                                       D+D  3He + n (2.45 MeV)
                    durisi@to.infn.it,    visca@to.infn.it          - April 18th, 2005             5
Water cooling                          HV power supply
(2 lines: 1- Low conductance water     120 kV – 300 mA
             for target
          2- standard water for void
             system, RF system,        HV relay
             HV power supply system.



Turbo pumping
system
Roughing pump                                       Pressure gauge
(up to 2 10-3 mbar)                                 controllers
Turbo pump
(<10-10 mbar)




RF power supply and matching
network (freq. 13.56 MHz, max.
transfer power 5000 W)                              Deuterium
                                                    gas flow
                                                    system
                                   Installation
December 2004                                                              High voltage
                                                                           flange and
The compact neutron generator                                              target
                                                                           assembly
has been installed in the former
irradiation room of the
synchrotron laboratory at the                                              Al3O2
Physics Institute                                                          insulator
TEST:
• low neutron flux,                                                        Vacuum
GOAL:                                                                      pumping
                                                                           chamber
• maximum neutron flux for
  BNCT application,
• final moderator design.
  Minimum neutron yield (from
 agreement with LBNL) > 1011 s-1

              durisi@to.infn.it,   visca@to.infn.it   - April 18th, 2005               7
         GOAL - Final moderator design:
         Beam Shaping Assembly (BSA)

Neutrons produced from DD fusion reaction (2.45 MeV) need to
        be moderated to lower energies for use in BNCT:
1. maintaining adequate beam flux,
2. minimizing undesired dose to the patient’s body and other
   non-tumour locations.

             The major components of BSA are:


                                              Gamma
MODERATOR          REFLECTOR                                      DELIMITER
                                             shielding


           durisi@to.infn.it,   visca@to.infn.it   - April 18th, 2005         8
    Assessment of a “good” BSA and
comparison between different configurations

                   Evaluation of
                FIGURES OF MERIT




                                     IN-PHANTOM FIGURES OF
FREE BEAM                            MERIT: calculation of depth
PARAMETERS                           dose profiles in healthy and
                                           tumour tissue




     durisi@to.infn.it,   visca@to.infn.it   - April 18th, 2005     9
                     BSA with MCNP: EXAMPLE
              Lithiated polyethylene= 5 cm                           Copper Plasma chamber
                                             Air                        + water cooling
                                                    RF antenna:
                          AlF3                     quartz outside,
                                                    water inside
                                  Al
                                                                                        Teflon
                          MgF2                                                          = 1 cm


                                                                                Al2O3
                           AlF3
                                                       Target: Al, water
                                                     cooling inside target
      Lead + Antimony                                   and Fe outside
                            Bismuth                                          Extraction grid +
x                                                   z                        water pipes


     y                                  y
    Epithermal column: 19 cm MgF2 + 6.5 cm Al + 10 cm MgF2 + 5
              Al + 5 air; beam exit window 20x20 cm2
     Distance: center of the source-beam exit window = 80 cm
                durisi@to.infn.it,     visca@to.infn.it        - April 18th, 2005                10
                           Free beam parameters

Neutron yield 1011 n/s- 120 kV, 300 mA                  Neutron yield 5 1012 n/s-160 kV, 1 A

Fepith [cm-2 s-1]                         2.41E6              1.2E8                1E8-1E9

Jepith [cm-2 s-1]                         1.46E6              7.3E7

Df / Fepith [Gy cm2]                     1.87 E-12           1.87 E-12             < 2E-13

Dg /Fepith [Gy cm2]                      3.42 E-13           3.42 E-13             < 2E-13

Jepith/Fepith                             0.607               0.607                >= 0.7




                    Recommended values for brain tumour
                        treatment IAEA-TECDOC-1223

                    durisi@to.infn.it,    visca@to.infn.it    - April 18th, 2005             11
                                       Neutron spectra (Neutron yield 1011 n/s)

                                                 Neutron Spectra at the beam exit window
                          8,00E+04

                                           Config: MgF2+Al+MgF2+Al
                          7,00E+04


                          6,00E+04
neutron flux [cm-2 s-1]




                          5,00E+04


                          4,00E+04


                          3,00E+04


                          2,00E+04


                          1,00E+04


                          0,00E+00
                                1,00E-09   1,00E-08   1,00E-07   1,00E-06   1,00E-05   1,00E-04   1,00E-03   1,00E-02   1,00E-01 1,00E+00 1,00E+01
                                                                            Neutron energy [MeV]



                                           durisi@to.infn.it,               visca@to.infn.it                 - April 18th, 2005                      12
              In phantom figures of merit
  Biological dose = DW = wg Dg + wn (DH + DN) + wB DB

• Gamma dose “Dg”, combination of the doses deriving from
  the beam and the photons induced by 1H(n,g)2H capture
  reaction with the hydrogen in tissue.

• Hydrogen dose “DH” or fast neutron dose due to proton-
  recoil reactions at the higher neutron energies (> 1 keV) in
  the tissue.

• Thermal neutron dose “DN”, due to the thermal neutron
  capture mainly by nitrogen nuclei 14N(n,p)14C.

• Boron dose “DB” , due to neutron capture reaction with
  boron.
           durisi@to.infn.it,   visca@to.infn.it   - April 18th, 2005   13
      Material       RBE for g        RBE for n       10B   (ppm)      10B   CBE
                       (wg)             (wn)                               (wB)
       Skin                1               3.2              15             2.5


    Soft tissue            1               3.2              10             2.5


      Healthy              1               3.2              10             1.3
    liver tissue
      Tumour               1               3.2              60             3.8
    liver tissue

                   Values used in all the simulations
These are the weighting factors commonly used for brain tumour

              durisi@to.infn.it,   visca@to.infn.it   - April 18th, 2005           14
The Anthropomorphic
   phantom ADAM

           durisi@to.infn.it,   visca@to.infn.it   - April 18th, 2005   15
                 BSA with MCNP: EXAMPLE
                                                        ICRU reference phantom
                                                       implemented in MCNP by
                                                           ENEA – Bologna
                                                                    SPINE    KIDNEYS




                                                               PANCREAS

                                                                                 SPLEEN


                                            ARM BONES                 STOMACH
                                                                                       RIB CAGE
                                                                 BLADDER               SURFACE

x                                                                             SKIN ON TRUNK
                                                     Liver segmentation
    y

        Cross section of the Anthropomorphic phantom ADAM


             durisi@to.infn.it,   visca@to.infn.it      - April 18th, 2005                    16
                                       Total dose rate in healthy and tumour tissue
                                                               10B                                  boron healthy tissue
                                                                     15 ppm in skin
                        4,50E-03                                                                    gamma
                                               Liver           10B   10 ppm in healthy liver        tot healthy tissue
                        4,00E-03                               10B                                  boron tumour tissue
                                                                     60 ppm in tumour liver
Dose rate [Gy-eq/min]




                                                                                                    tot tumour tissue
                        3,50E-03

                        3,00E-03

                        2,50E-03
                                       Skin
                        2,00E-03
                                         Soft tissue
                        1,50E-03

                        1,00E-03

                        5,00E-04

                        0,00E+00
                                   0       2           4         6             8           10           12                 14

                                                            Depth in trunk [cm]

                                       durisi@to.infn.it,   visca@to.infn.it          - April 18th, 2005                        17
                 In phantom figures of merit

Advantage Depth [cm]               8.33

Advantage Depth Dose              1.16E-3               Neutron yield = 1011 n/s
Rate [Gy-eq/min]
Treatment Time [h]                143,65              Dose limit healthy tissue:
                                                              10 Gy-eq;
Terapeutic Depth [cm]              6.13
                                                      TT = 10/1.16E-3 = 143.65 h
Peak Therapeutic Ratio             3.60



             If the neutron yield is equal to 5 1012 n/s,
             ADDR = 5.8 E-2                           TT = 2.87 h


             durisi@to.infn.it,    visca@to.infn.it      - April 18th, 2005        18

				
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