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

G. Bartesaghi, 11° ICATPP, Como, 5-9 October 2009

OutlineOutline

• Boron Neutron Capture Therapy (BNCT): Boron Neutron Capture Therapy (BNCT): a brief introductiona brief introduction

• Dosimetry and treatment planning in BNCTDosimetry and treatment planning in BNCT

• NRI-Rez BNCT facilityNRI-Rez BNCT facility

• Materials & Method: Materials & Method:

•MC simulations: source and phantoms MC simulations: source and phantoms descriptiondescription

• Fricke gel dosimetersFricke gel dosimeters

• Results and conclusionsResults and conclusions

G. Bartesaghi, 11° ICATPP, Como, 5-9 October 2009

10B 1n 11B* 7Li 4He

Gamma(477 keV)

1010B (n,B (n,))77LiLi (( = 3837 b) = 3837 b)

NeutronsNeutrons from nuclear from nuclear reactorsreactors

Boron Boron selectively selectively accumulated in accumulated in tumor cellstumor cells

Boron Neutron Capture Boron Neutron Capture TherapyTherapy

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)

- 1010B concentration on-line monitoringB concentration on-line monitoring

TP software should be capable to display

isodose curves, superimposed to the anatomical images

Reactor geometry

Patient anatomical images Boron

concentration

Treatment planning in Treatment planning in BNCTBNCT

G. Bartesaghi, 11° ICATPP, Como, 5-9 October 2009

BNCT facility at NRI – Rez (Prague)BNCT facility at NRI – Rez (Prague)

LVR-15 reactor

Epithermal column

Epithermal neutron flux:

7∙108 cm-2 s-1

Nuclear reactor power:

9 MW

G. Bartesaghi, 11° ICATPP, Como, 5-9 October 2009

Thermal neutrons: < 0.4 eVThermal neutrons: < 0.4 eV

Epithermal neutrons: 0.4 eV < EEpithermal neutrons: 0.4 eV < Enn < 10 keV < 10 keV

Fast neutrons: > 10 keVFast neutrons: > 10 keV

G. Bartesaghi, 11° ICATPP, Como, 5-9 October 2009

Treatment room

Control room

G. Bartesaghi, 11° ICATPP, Como, 5-9 October 2009

Fixation mask

12 cm diameter

collimator

G. Bartesaghi, 11° ICATPP, Como, 5-9 October 2009

Radiation transport and interactions in tissue-equivalent Radiation transport and interactions in tissue-equivalent phantomsphantoms

MC MC calculationscalculations

- Neutron transport and Neutron transport and thermalizationthermalization- Boron doseBoron dose

- Neutron doseNeutron dose

MCNP5 MCNP5 codecode

Source plane Source plane technique technique (used with (used with MacNCTPLAN):MacNCTPLAN):- energy distributionenergy distribution

- radial distributionradial distribution

- divergence distributiondivergence distribution

G. Bartesaghi, 11° ICATPP, Como, 5-9 October 2009

Tissue equivalent phantomsTissue equivalent phantoms

Standard water Standard water phantomphantom

50x50x25 cm50x50x25 cm33

Cylindrical water-Cylindrical water-equivalent phantomequivalent phantom

d: 16cm, h: 14cmd: 16cm, h: 14cm

G. Bartesaghi, 11° ICATPP, Como, 5-9 October 2009

Phantoms reproduced in Phantoms reproduced in MCNP5MCNP5

-Neutron flux on the central planeNeutron flux on the central plane

- Boron dose in 0.5 cmBoron dose in 0.5 cm33 cells cells

- Neutron dose along the beam axis- Neutron dose along the beam axis

G. Bartesaghi, 11° ICATPP, Como, 5-9 October 2009

Fricke solution + Xylenol Orange = Fricke solution + Xylenol Orange = radiochromicradiochromic

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.

0 2 4 6 8 10 12 14

0,65

0,66

0,67

0,68

0,69

0,70

Dd /

Dp

Depth (cm)

(OD)(OD)stst = = αα11DDγγ + + αα22DDnpnp

(OD)(OD)hw hw = = αα33DDγγ + + αα44DDndndf = Df = Dndnd/D/Dnp np

= = 0.66±0.010.66±0.01

from Monte from Monte CarloCarlo

G. Bartesaghi, 11° ICATPP, Como, 5-9 October 2009

0 2 4 6 8 10 12 14

0

1

2

3

4

5

6

7

8

9

Dos

e ra

te (

Gy/

h)

Depth (cm)

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