G. Bartesaghi, 11° ICATPP, Como, 5-9 October 2009 MONTE CARLO SIMULATIONS ON NEUTRON MONTE CARLO SIMULATIONS ON NEUTRON TRANSPORT AND ABSORBED DOSE IN TISSUE- TRANSPORT AND ABSORBED DOSE IN TISSUE- EQUIVALENT PHANTOMS EXPOSED TO HIGH- EQUIVALENT PHANTOMS EXPOSED TO HIGH- FLUX EPITHERMAL NEUTRON BEAMS FLUX EPITHERMAL NEUTRON BEAMS G. Bartesaghi, G. Gambarini, A. Negri Department of Physics of the University of Milan and INFN, Milan, Italy J. Burian, L. Viererbl Department of Reactor Physics, Nuclear Research Institute Rez, Czech Republic
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G. Bartesaghi, 11° ICATPP, Como, 5-9 October 2009 MONTE CARLO SIMULATIONS ON NEUTRON TRANSPORT AND ABSORBED DOSE IN TISSUE-EQUIVALENT PHANTOMS EXPOSED.
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G. Bartesaghi, 11° ICATPP, Como, 5-9 October 2009
MONTE CARLO SIMULATIONS ON MONTE CARLO SIMULATIONS ON NEUTRON TRANSPORT AND NEUTRON TRANSPORT AND ABSORBED DOSE IN TISSUE-ABSORBED DOSE IN TISSUE-
EQUIVALENT PHANTOMS EXPOSED TO EQUIVALENT PHANTOMS EXPOSED TO HIGH-FLUX EPITHERMAL NEUTRON HIGH-FLUX EPITHERMAL NEUTRON
BEAMSBEAMSG. Bartesaghi, G. Gambarini, A. Negri
Department of Physics of the University of Milan and INFN, Milan, Italy
J. Burian, L. Viererbl
Department of Reactor Physics, Nuclear Research Institute Rez, Czech Republic
Emission of low range, high LET ions:Emission of low range, high LET ions:44HeHe2+2+ (1.47 MeV) (1.47 MeV) 77LiLi3+3+ (0.84 MeV) (0.84 MeV)
with a range in tissue about one cell with a range in tissue about one cell diameter.diameter.
G. Bartesaghi, 11° ICATPP, Como, 5-9 October 2009
Dosimetry in BNCTDosimetry in BNCTWhat has to be What has to be
measured?measured? DDtottot
IIII DDBB ++ DDpp
++ DDnn
++
DD
““therapeutic dose”, from therapeutic dose”, from 1010B(n,B(n,))77Li Li = 3837 b = 3837 b
from from 1414N(n,p)N(n,p)1414C EC Epp= 630 keV= 630 keV = 1.9 b = 1.9 b
due to epithermal and fast neutron due to epithermal and fast neutron scattering mainly on H nuclei scattering mainly on H nuclei
from from 11H(n,H(n,γγ))22H EH Eγγ = 2.2 MeV = 2.2 MeV = 0.33 b = 0.33 b and reactor backgroundand reactor background
High complexity: four components, each with different LET and High complexity: four components, each with different LET and different RBE !!!different RBE !!!
G. Bartesaghi, 11° ICATPP, Como, 5-9 October 2009
Three distinct modules are necessary:
- dosimetry with an appropriate phantomdosimetry with an appropriate phantom
- Monte Carlo based treatment planning Monte Carlo based treatment planning (TP)(TP)
very good tissue equivalencevery good tissue equivalence thin layers (up to 3mm thick):thin layers (up to 3mm thick):
Fricke Gel dosimeters in form of Fricke Gel dosimeters in form of layerslayers
• not affecting the in-phantom neutron not affecting the in-phantom neutron transporttransport• it is possible to modify the gel it is possible to modify the gel composition in order to achieve dose composition in order to achieve dose components separationcomponents separation
Standard GelStandard Gel -rays and fast neutrons (recoil-protons)-rays and fast neutrons (recoil-protons)
Standard-Gel added with Standard-Gel added with 1010B (40 ppm)B (40 ppm) -rays, fast neutrons, -rays, fast neutrons, and and 77Li particlesLi particles
Gel like Standard-Gel made with heavy water Gel like Standard-Gel made with heavy water -rays and fast neutrons (recoil-deuterons)-rays and fast neutrons (recoil-deuterons)
G. Bartesaghi, 11° ICATPP, Como, 5-9 October 2009
Boron doseBorated gelStandard gel
Boron dose
Dose images Dose images (15x12 cm(15x12 cm22) in ) in the standard the standard water phantomwater phantom
G. Bartesaghi, 11° ICATPP, Como, 5-9 October 2009
2 4 6 8 10 12 14
0
1x108
2x108
3x108
4x108
-8
-4
048
Flu
x (c
m-2
s-1)
Wid
th (c
m)
Depth (cm)
2 4 6 8 10 1214
0
1x108
2x108
3x108
4x108
-8
-40
48
Wid
th (c
m)
Flu
x (c
m-2
s-1)
Depth (cm)
2 4 6 8 10 1214
0
1x107
2x107
3x107
4x107
-8
-40
48
Flu
x (c
m-2
s-1)
Wid
th (c
m)
Depth (cm)
Thermal neutron fluxThermal neutron flux
Epithermal neutron Epithermal neutron fluxflux
Fast neutron fluxFast neutron flux
Standard Standard phantomphantom
G. Bartesaghi, 11° ICATPP, Como, 5-9 October 2009
2 4 6 8 10 1214
0
1x107
2x107
3x107
4x107
-8
-40
48
Flu
x (c
m-2
s-1)
Wid
th (c
m)
Depth (cm)
Thermal neutron fluxThermal neutron flux
Epithermal neutron Epithermal neutron fluxflux
Fast neutron fluxFast neutron flux
Cylindrical Cylindrical phantomphantom
2 4 6 8 10 12 14
0
1x108
2x108
3x108
4x108
-8
-4
048
Flu
x (c
m-2
s-1)
Wid
th (c
m)
Depth (cm)
2 4 6 8 10 1214
0
1x108
2x108
3x108
4x108
-8
-40
48
Flu
x (c
m-2
s-1)
Wid
th (c
m)
Depth (cm)
G. Bartesaghi, 11° ICATPP, Como, 5-9 October 2009
-8 -6 -4 -2 0 2 4 6 8 100
2
4
6
8
10
12
14Standardphantom
Dos
e R
ate
(Gy/
h)
Width (cm)
Gel data MC data
Cylindricalphantom
Boron dose distributionBoron dose distribution
Transverse profiles at 3 cm depth
G. Bartesaghi, 11° ICATPP, Como, 5-9 October 2009
Boron dose distributionBoron dose distribution
Transverse profiles at in the cylindrical phantom at different depths
-8 -6 -4 -2 0 2 4 6 80
2
4
6
8
10
12
14
5.75 cm
2.75 cmD
ose
Rat
e (G
y/h)
Width (cm)
Gel data MC data
8.75 cm
Cylindrical phantom
G. Bartesaghi, 11° ICATPP, Como, 5-9 October 2009
Boron dose distributionBoron dose distribution
In-depth on-axis profiles
in the two phantoms
0 2 4 6 8 10 12 140
2
4
6
8
10
12
14
Gel data MC
Dos
e ra
te (
Gy/
h)
Depth (cm)
Standard phantom
0 2 4 6 8 10 12 140
2
4
6
8
10
12
14Cylindrical phantom
Gel data MC data
Dos
e ra
te (
Gy/
h)
Depth (cm)
G. Bartesaghi, 11° ICATPP, Como, 5-9 October 2009
0 2 4 6 8 10 120,10
0,15
0,20
0,25
0,30
0,35
0,40
0,45
(O
D)
Depth (cm)
Standard gel Heavy water gel
Fast neutron and gamma doses separationFast neutron and gamma doses separation
Central profile in the Central profile in the standard water phanton.standard water phanton.
Gamma dose (gel) Gamma dose (TLD) Fast neutrons dose (gel) Fast neutrons dose (IC)
Central profile in the standard water Central profile in the standard water phantom.phantom.
(1) Binns et al., Med Phys, 32 (12), 2005
G. Bartesaghi, 11° ICATPP, Como, 5-9 October 2009
ConclusionsConclusions
• Neutron transport, boron dose and Neutron transport, boron dose and neutron dose in tissue-equivalent neutron dose in tissue-equivalent phantoms have been calculatedphantoms have been calculated
• Boron and fast neutron doses have been Boron and fast neutron doses have been measured by means of Fricke gel layersmeasured by means of Fricke gel layers
• The good agreement confirms the The good agreement confirms the accuracy of the source model used for TPaccuracy of the source model used for TP