[ DOI: 10.7508/ijrr.2015.01.002 ]
Volume 13, No 1
International Journal of Radiation Research, January 2015
Optimization study for BNCT facility based on a DT
neutron generator
J.G. Fantidis1*, A. Antoniadis2
1DepartmentofElectricalEngineering,TechnologicalEducationInstituteofEasternMacedoniaandThrace,Saint
Loucas,Kavala,Greece
2CardiovascularDivision,BrighamandWomen'sHospital,HarvardMedicalSchool,Boston,USA
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ABSTRACT
►
Original article
*Correspondingauthor:
Dr.J.G.Fantidis,
Fax:+302510462315
E-mail:[email protected]
Revised: April 2014
Accepted: Sept. 2014
Int. J. Radiat. Res., January 2015;
13(1): 13-24
DOI: 10.7508/ijrr.2015.01.002
Background: A Boron Neutron Capture Therapy (BNCT) facility, based on a DT
neutron generator, with the final goal to find out a poten al, alterna ve,
solu on to exis ng BNCT treatment facili es which are based on nuclear
reactors is examined. Materials and Methods: With the aim of the MCNP4B
Monte Carlo code different beam-shaping assembly (BSA) configura ons
were considered. Lead was selected as reflector material while CF2, D2O,
Fluental, PbF4, PbF2, BiF3, BiF5, MgF2, Al2O3, AlF3, TiF3, BeD2, CaF2 and 7LiF were
examined as spectrum shi3ers. In order to improve the quality of the beam
tanium, nickel-60, iron and tanium alloy (Ti6Al14V) were simulated as fast
neutrons filters while lead and bismuth were considered as gamma filters.
Results: An extensive set of calcula ons performed with MCNP4B Monte
Carlo code have shown that the combina on of 7LiF which accommodates a
conic part made of D2O, then followed by a TiF3 layer is the op mum
moderator design. The use of three different materials for further reduc on
of fast neutrons, thermal neutrons and gamma rays is necessary. 60Ni, Cd and
Bi were chosen respec vely for these purposes. The epithermal neutron flux
obtained at the beam exit window turned out to be 3.94×109 n cm-2 s-1 while
fulfilling all the recommended IAEA in-air Figure Of Merit (FOM) criteria. The
assessment of the dose profiles in head phantom and the in-phantom FOM
are also presented. Conclusion: The proposed assembly configura on may
provide an a>rac ve op on for centers wishing to install a BNCT facility.
Keywords: BNCT, DT neutron generator, epithermal neutron, MCNP.
INTRODUCTION
havehighLinearEnergyTransfer(LET),andan
associatedhighRelativeBiologicalEffectiveness
(RBE). Themean free path is about7 μmand 4
BoronNeutronCaptureTherapy(BNCT)isan
μm for α particle and for 7Li, respectively.
effective and promising treatment of tumor
Considering that the mean cellular diameter is
types which are resistant to conventional
almost in the same order of magnitude, the
therapies.BNCTisabinarytreatmentmodality,
10
BNCT technique may therefore be effective in
irst a B compound is delivered to the patient
selectivetumorcelldestruction(1,2).
and differently accumulates in cancer cells
Duetotheirpoortissuepenetration,thermal
versus healthy tissue; then, when a high boron
neutrons
are only applicable to the direct
concentration ratio between tumor and healthy
treatment
of
tumors which are located near the
tissue is reached, the patient is irradiated with
10
7
tissue surface. Epithermal neutrons with an
neutrons inducing the B(n,α) Li reaction. The
energyrangebetween1eVand10keVaremore
alphaparticleemittedandthe 7Linucleicreated
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[ DOI: 10.7508/ijrr.2015.01.002 ]
Fantidis and Antoniadis / Optimization study for BNCT facility based on a DT neutron generator
(4,5,9-12).
penetrating and able to reach deep-seated
Themaingoalofthisstudywastooptimizea
tumors.AtypicalexampleisglioblastomamultiBNCTfacilitybasedonaDTneutrongenerator-
formaquiteaggressivetypeofbraincancer,by
whichyields1014ns-1-intermsofbeamshaping
farthemostcommonandmalignantoftheglial
assembly (BSA) design (moderator, gamma ray,
tumors. The application of the BNCT technique
fast and thermal neutron ilters) and calculate
inclinicaltrialsrequiresaneutronbeamhaving
the dose in a simulated head phantom. The
a high enough lux level and, mainly, a proper
facility was designed using the Monte Carlo
spectrum shape. In order to reduce the irradiaMCNP version 4B, transport code which is
tiontime,thedesirableminimumbeamintensity
suitableforgammaandneutroncalculations(13).
9
-2
-1
should be 1×10 cm s . In order to limit the
treatmenttimetoreasonablelevels(i.e.1hour)
the requested epithermal neutron lux level
MATERIALSANDMETHODS
shouldbeatleast109s-1,andalsowellcollimated to avoid excessive dose to adjacent healthy
Neutronsource
tissues(3-5).
DT tubes are based upon deuteron beams
A number of candidate neutron sources for
bombardingatritiatedtargetwiththeresultant
BNCT technique can be considered. Neutrons
yield of fusion neutrons. The neutron spectrum
may be generated by nuclear reactors,
from the DT neutron generator, which was deaccelerator-driven systems or generators based
rivedbyFantidisetal. (14),hasbeenusedforthe
on either spontaneous ission of transuranic
purposesofthispaper.Inordertominimizethe
heavy materials, or exploiting speci ic nuclear
treatmenttimeinBNCTtheepithermalneutron
reactionsinducedbyradioactivesources.Radio252
241
lux has to be suf iciently high (≈109n cm-2s-1).
isotopesources,suchas Cfand Am/Beare
AccordingtoRasoulietal. (11)a ission-converter
commonly used for detector calibrations
-based sphere made by natural uranium
because of low yield and energy up to 10 MeV.
surroundingtheDTsourcetargetcouldbeused
Nuclearreactorsprovidehigh-intensityneutron
as neutron multiplier and energy degrader
beamsbutareveryexpensiveandconsiderably
device in order to increase the number of
sizeable to be used in hospital settings.
neutrons via ission reaction. Based on results
Additionally, safety and authorization concerns
prevent their installation in urban hospitals. from the MCNP4B calculations, the ratio of
neutrons yielded (mainly by ission reactions)
Accelerator-driven systems, based on linacs,
per source neutron (N/N0), available over the
cyclotrons,ortandemvandeGraffmayinstead
surface of such a sphere, is peaked for 14 cm
be properly used to yield and tailoran epitherradius( igure1).Theseresultsaresimilartothe
malneutronbeamforthispurpose.Theircostis
generally lower compared to even smallprevious studies by Martin and Abrahantes(12)
andRasoulietal.(11).
researchreactors,althoughtheyneedaseriesof
ancillarysystemswhichmayoccupylargespace
(6-8).
TheMCNPfacilitymodeling
Different beam-shaping assembly (BSA)
DT neutron generators, based on the fusion
3
4
con
igurations were considered, in order to
reaction H(d,n) He,maybeanattractivechoice
ful ill the parameters required (table 1) (15).
as they warrant high safety, smaller size and
Basedontheliterature,lead(Pb)wasselectedas
high social acceptability. Furthermore, these
re lector material (8,9). Because of the high
neutron sources require low energy deuteron
(14.1MeV)meanenergyneutronsyieldedbyDT
beam (100–400 keV) which is available with
reactions,aspectrumshiftersystemisneededin
smaller,simpler, electrostatic-type accelerators.
order to slow neutrons down to the required
Lastbutnotleasttheyofferanon/offswitching
epithermal energy range (1 eV to 10 keV). In
of the emitted neutrons and are less costly. A
number of studies on the use of DT neutron order to achieve such a goal, the "ideal"
generators for BNCT were recently publishedspectrum shifter should provide the following
Int. J. Radiat. Res., Vol. 13 No. 1, January 2015
14
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[ DOI: 10.7508/ijrr.2015.01.002 ]
Fantidis and Antoniadis / Optimization study for BNCT facility based on a DT neutron generator
Neutrons, once being moderated pass
nuclearproperties:alowdownscatteringcross
through ilters,inordertoimprovethequalityof
section at the epithermal energy range, high
neutron beam. An ideal neutron ilter must
removal cross section at higher energies and
absorb only the unwanted fast and thermal
limited radiative (n, γ) captures. In addition, it
neutrons without producing gamma rays.
should not produce large quantities of gammaUnfortunately such nuclear properties are not
raysbyinelasticscattering.Inordertoproduce
ful illedbyexistingmaterials,eitherinelemental
anepithermalbeam,themostsuitablematerials
orcompoundforms.Abalancedcompromisehas
to moderate neutrons with different combinatherefore to be taken. For such a reason, the
tions and thickness were therefore investigated
selection has been limited to four different
by Monte Carlo simulations. Fourteen different
materialsabletoimprovethespectrumshapeof
materials namely, Te lon (CF2), heavy water
the neutron beam: Titanium (Ti), Nickel-60
(D2O), Fluental, PbF4, PbF2, BiF3, BiF5, MgF2,
7
(60Ni), Iron (Fe) and titanium alloy (Ti6Al14V).
Al2O3, AlF3, TiF3, BeD2, CaF2 and LiF were
They have proven to be effective as neutron
considered.
iltering materials aiming to improve the
Figure 1. Number of neutrons per neutron source for different thicknesses of natural uranium as a neutron
mul plier.
Table 1. Recommended values in the beam exit window.
BNCT beam port parameters
-2 -1
Φepithermal (n cm s )
~109
Φepithermal/Φfast
>20
Φepithermal/Φthermal
>100
2
15
Recommended value
Ḋfast/Φepithermal (Gy cm )
<2 × 10-13
Ḋγ/Φepithermal (Gy cm2)
<2 × 10-13
Fast energy group (Φfast)
E>10 keV
Epithermal energy group (Φepithermal)
1 eV ≤ E ≤ 10 keV
Thermal energy group (Φthermal)
E<1 eV
Int. J. Radiat. Res., Vol. 13 No. 1, January 2015
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[ DOI: 10.7508/ijrr.2015.01.002 ]
Fantidis and Antoniadis / Optimization study for BNCT facility based on a DT neutron generator
epithermal to fast neutron ratio in the BNCT
differentthickness,werethereforeinvestigated.
neutron beam. High Z materials, such as lead
Figure 2 shows the Φepithermal for the studied
(Pb) and Bismuth (Bi) are instead suitable in
materialsasafunctionofthemoderators'thickorder to remove the gamma component.
ness.In igure3theΦepithermal/ΦfastratioofspecMoreover,inordertoincreasetheepithermalto
trum shifter candidate materials versus their
thermalratiomaterialshavingahighabsorption
thickness,isplotted.Accordingtotheresultsthe
cross section in thermal range are needed. An
BeD2andtheD2OgivethehigherΦepithermalshort
absorber material, lithiated poliethylene (polymoderatorslength,althoughthe luxlevelquickly drops off with increasing thickness. Taking
Li),isatlastincludedasdelimitedtogetacolliinto account plots in igures 2 and 3, it may be
mated neutron beam. The inal part of the BSA
designincludesadelimiterwiththeintentionto
concludedthat19cmthicknessof 7LiFprovides
minimize the dose rate outside of the tumor
the optimal balance between Φepithermal and
cells.Itshouldbenotedthattheunitisdesigned
Φepithermal/Φfastratiocorrespondingly.
intheformofcoaxialcylindersandtheneutron
With the aim to ind out the best solution a
huge number of con igurations have been
distribution is symmetrical due to the symmetconsideredandthesimulationsshowthat19cm
ricalgeometryconsidered.
of 7LiF housing at the beam axis an additional,
truncated cone volume illed with D2O is the
RESULTS
optimumchoice.Thetruncatedconemoderator
has a length of 6 cm and radii 6 and 1 cm with
Awidesetofcomputationalstudieswascarthe larger radius close to the source. The conic
ried out using the MCNP4B Monte Carlo code.
part increases the Φepithermal and the Φthermal and
reducestheΦfast.Particularlytheintroductionof
The neutron lux and the dose rate were calculated at the exit of the facility across the 12 cm
the D2O increases the Φepithermal more than 7%
(3.04×1010ncm-2s-1vs.2.84×1010ncm-2s-1)and
diameter window using the F2, Fm2 tallies and
the DE, DF cards. An accuracy of less than 1%
improves the Φepithermal/Φfast and the Φepithermal/
was achieved in all cases. Fourteen different
Φthermal by 9.89% and 0.87% respectively. However, both the Φepithermal/Φfast and the Φepithermal/
spectrum shifter materials to slow neutrons
down to epithermal energy ranges, having Φthermal ratios have values (2.89 and 10.49
Figure 2. Φepithermal for different thicknesses of moderators.
Int. J. Radiat. Res., Vol. 13 No. 1, January 2015
16
TiF3seemtobehoweverabetterchoicebecause
correspondingly)belowfromtherecommended
of superior values for Φepithermal/Φfast and the
limits. For these reasons a second moderator
Φepithermal/Φthermal BSA modeling parameters.
shouldbeused.
Indeed if TiF3 is selected as spectrum shifter
Figures 4, 5 and 6 show the Φepithermal,
instead of Fluental the BSA shows to have
Φepithermal/Φfast and the Φepithermal/Φthermal ratios
for a number of materials which have beencomparable values for the Φepithermal, a better
performancefortheΦepithermal/Φfastratioandby
selectedassecondspectrumshifterversustheir
far higher valuesfor theΦepithermal/Φthermal ratio.
thicknesses, whilst 19 cm 7LiF incorporating a
Therefore results revealed that the optimum
D2O conic part has previously been selected as
thicknessfortheTiF3spectrumshifteris19cm.
the irst part of the moderator. Even though
FluentalisabletoprovidealargerΦepithermal,the
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[ DOI: 10.7508/ijrr.2015.01.002 ]
Fantidis and Antoniadis / Optimization study for BNCT facility based on a DT neutron generator
Figure 3. The Φepithermal/Φfast ra o for different thicknesses of moderators.
Figure 4. Φepithermal for different
thicknesses of the second
moderator where 19 cm 7LiF
which incorporates a cone
made of D2O are selected as the
first part of the moderator.
17
Int. J. Radiat. Res., Vol. 13 No. 1, January 2015
[ DOI: 10.7508/ijrr.2015.01.002 ]
Fantidis and Antoniadis / Optimization study for BNCT facility based on a DT neutron generator
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Figure 5. The Φepithermal/Φfast
ra o for different thicknesses of
the second moderator where
19 cm 7LiF which incorporates a
cone made of D2O are selected
as the first part of the
moderator.
Figure 6. The Φepithermal/Φthermal
ra o for different thicknesses of
the second moderator where
19 cm 7LiF which incorporates a
cone made of D2O are selected
as the first part of the
moderator.
The BSA con iguration thus selected allows
forimprovingthequalityoftheinairFOMbeam
parameters, but the DNfast/Φepithermal (4.57×10-13
Gy cm2) and the DNγ/Φepithermal (4.01×10-12 Gy
cm2)ratiosturnsouttobeabovethe ixedlevels. The value of the DNfast/Φepithermal shows that
theproperselectionsforafastneutron ilteris
required in order to optimize the BSA design.
Therefore4differentmaterials(Fe,Ti6Al14V,Ti,
60Ni) were examined as fast neutron ilters. In
Int. J. Radiat. Res., Vol. 13 No. 1, January 2015
igure 7 plots of the calculated DNfast/Φepithermal
ratio for different thickness of the investigated
ilters, shows that 60Ni is a better choice. Howeverthebeamspectraowingtothefastneutron
ilters show ( igure 8) that the presence of the
Ti ensures higher Φepithermal with slightly lower
valuesfortheDNfast/Φepithermalratio.Motivatedby
these results all the BNCT in-air FOM parameters have been calculated and the results are
summarizedintable2.Fromsuchresultsitmay
18
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[ DOI: 10.7508/ijrr.2015.01.002 ]
Fantidis and Antoniadis / Optimization study for BNCT facility based on a DT neutron generator
benotedthattheTi iltercomparedwiththe60Ni
provideshigherΦepithermalandhasslightlyhigher
value for the Φepithermal/Φthermal ratio. However
the inalchoiceforthefastneutron ilteris 60Ni
(withthickness5cm)becausenotonlypresents
comparable values for the Φepithermal, Φepithermal/
Filter
Table 2. The relevant with BNCT parameters for 5cm thickness of the inves gated fast neutrons filters.
Φepithermal
Φepithermal/Φfast Φepithermal/Φthermal Ḋfast/Φepithermal
Ḋγ/Φepithermal
Fe
Ti6Al14V
Ti
60
Φthermal, Φepithermal/Φfast and DNfast/Φepithermal but
also shows a basically lower level for the DNγ/
Φepithermal ratio. This fact is very important
becauserequirealessthickgamma ilterwithan
improvement on the Φepitermal level as well,
comparedwithTior60Ni.
Ni
IAEA criteria
(×109n cm-2s-1)
4.31
5.55
7.52
33.07
46.02
72.61
6.71
>1
78.94
>20
96.30
23.11
34.54
(×10–13 Gy cm2)
2.60
2.65
2.14
(×10-13 Gy cm2)
2.11
2.27
2.88
31.94
>100
1.96
<2
1.06
<2
Figure 7. The Ḋfast/Φepi ra o for
different thicknesses of fast
neutrons filters.
Figure 8. The neutron spectra
for 5cm thickness of the
inves gated fast neutrons
filters.
19
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Fantidis and Antoniadis / Optimization study for BNCT facility based on a DT neutron generator
The Φepithermal/Φthermal ratio can be further
raised up above the recommended level by using a thin layer of thermal neutron absorber.
Just0.15cmofCadmium(Cd)isindeedenough
to absorb a large fraction of thermal neutrons
withanegligiblepartofepithermalones.Onthe
contrary Cadmium has the drawback of a high
energygammaraysyielduponneutroncapture
but this problem may be overcome if the Cd
thermalneutron ilterplacedbeforeofagamma
shield (16). Gamma rays can be attenuated by
using appropriate high-Z materials such as the
BiorPb.Biiscommonlyused,sinceitprovides
photonattenuationcomparabletothatfromPb,
while limiting the absorption for the neutron
beam. Results of comparative calculations are
summarized in table 3. Therefore 5.5 cm thickness Bi gamma shielding, completed by 2 cm
thickness delimiter made of poly-Li is the last
partoftheBSAstudywhichisshownin igure9.
Neutron spectra of the proposed facility, calculated in three con igurations, without ilters,
with5cm60Nifastneutron ilterandforthe inal
BSA con iguration are shown in igure 10. The
pro ile of the Φepithermal in front of the BSA is
shownin igure11.
In this study the Snyder’s head phantom,
whichwasderivedbytheMCNPsample iles,is
simulated using MCNP4B code. This phantom
consists of three ellipsoids for scalp, skull bone
and brain. The dimensions and the chemical
composition for an adult proceed from ICRU46
Table 3. The BNCT parameters for different gamma ray filters.
Configura7on
Φepithermal
Ḋfast/Φepithermal
Ḋγ/Φepithermal
Φepithermal/Φfast
Φepithermal/Φthermal
3.94
52.29
107.95
0.179
1.27
3.53
56.70
139.18
0.241
1.90
>1
>20
>100
<2
<2
(×109n cm-2s-1)
(×10–13 Gy cm2) (×10-13 Gy cm2)
7
LiF, D2O, TiF3 moderators
+ 60Ni fast neutron filter +
Cd thermal neutron filter +
5.5cm Bi
7
LiF, D2O, TiF3 moderators
+ 60Ni fast neutron filter +
Cd thermal neutron filter +
4.5 cm Pb
IAEA criteria
Figure 9. Geometric configura on of the BNCT system -not in scale.
Int. J. Radiat. Res., Vol. 13 No. 1, January 2015
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[ DOI: 10.7508/ijrr.2015.01.002 ]
Fantidis and Antoniadis / Optimization study for BNCT facility based on a DT neutron generator
Figure 10. The neutron spectra
at the exit of the facility with
and without filters.
Figure 11. The profile of the
Φepithermal in front of the
suggested BSA modeling.
(17).
The spatial distribution of the Φthermal,
wBis1.3forboronintissueand3.8forboronin
Φepithermal and Φfast in the head phantom along
the tumor. In the tumor, a 10B concentration of
the beam axis for Z direction are illustrated in
40 ppm was assumed and a 4:1 ratio of 10B in
igure 12. According to the results the Φepithermal
tumor to healthy brain was also assumed (9).
and Φfast have the maximum values at the scalp
Figure13showsthecalculateddoseratesinthe
andthe luxleveldropsoffwithincreasingthicktumor and healthy tissues at different depth in
theheadphantom.
ness.ThemaximumΦthermaloccursatadepthof
1.5–2.6cm.
The total absorbed tissue doses (DT) are
DISCUSSION
obtained by combining the four individual dose
components, namely gamma ray dose (Dγ), fast
neutron dose (Dfast), nitrogen dose (DN), boron
Inordertoevaluatetheproposedfacilitythe
dose (DB), weighted by their RBE (relative bioresults are compared with other published
logicaleffectiveness)factors,usingtheequation:
studies which are based on DT or DD neutron
DT=wγ×Dγ+wfast×Dfast+wN×DN+DB×wB
generator(table4).Theseresults(unacceptable
wherewγis1,wNandwfastaretakenas3.2while
values are in italic letters) indicate that only 2
21
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[ DOI: 10.7508/ijrr.2015.01.002 ]
Fantidis and Antoniadis / Optimization study for BNCT facility based on a DT neutron generator
facilities satisfy all the recommended by IAEA
criteria; the excellent extensive research from
Rasouli etal. (11) and the study are presented
which optimizes the previous BSA con igurations. As shown in table 4 the proposed facility
compared with the study from Rasouli etal.
improves the Φepithermal/Φfast ratio by a factor of
∼2.2. At the same time reduces the DNfast/
Φepithermal and the DNγ/Φepithermal by 3.7 and 1.6
times respectively while decreasing the
Table 4. Comparison of the proposed facility with some published works (based on DT or DD neutron generator).
Facility
IAEA criteria
Proposed facility
Rasouli and Masoudi
(2012) (10)
Rasouli et al. (2012) (11)
Cerullo et al., 2004 best
configura on (4)
Cerullo et al., 2002 final
configura on (23)
Montagnini et al.
(2002) (24)
Fan dis et al. (2013) (18)
Neutron yield
Φepithermal
(×1014 n s-1) (×109n cm-2s-1)
>109
1
3.94
Φepithermal/
Φfast
>20
52.29
Φepithermal/
Φthermal
>100
107.95
Ḋfast/Φepithermal Ḋγ/Φepithermal
(×10–13 Gy cm2) (×10-13 Gy cm2)
<2
<2
0.179
1.27
0.05
1.04
20.21
-
0.67
5.79
1.45
4.43
23.75
121.2
0.59
1.98
4
2.51
14.4
114.5
3.45
0.21
1
0.66
23.2
133
3.19
1.1
0.187
0.29
19.8
16.6
6.3
7.3
0.001
0.00117
20.81
128.81
0.00011
0.00023
Figure 12. Distribu on of
Φthermal, Φepithermal and Φfast in
the human head phantom.
Figure 13. Comparison of depth
dose profile between tumor
and normal ssue.
Int. J. Radiat. Res., Vol. 13 No. 1, January 2015
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Fantidis and Antoniadis / Optimization study for BNCT facility based on a DT neutron generator
which can reach relevant deeply into the brain
Φepithermal/Φthermal ratio by only ∼10.9%. The
(AD has value about 6 cm). The TT parameter
comparisonbetweentheproposedfacilitywitha
which indicates the treatment time has a very
similar facility which proposed by Fantidis etal.
(18)andbasedonDDneutrongeneratorindicates
attractive value (less than 20 min indicating a
reasonable treatment time) as a result of the
thattheuseofDTneutrongeneratorisbyfarthe
relativelyhighfepithermalvalue.
best solution owing to the fact that DT neutron
source provides signi icant higher Φepithermal values. Considering that DT neutron generators
14
-1
having10 ns neutronoutputmaybefeasible
CONCLUSION
theproposedfacilitymightbetakenintoaccount
BNCT is a potentially very useful cancer
asanalternativeforclinicswhichcannotafford
treatment modality; however only a few
tobuildandmaintainasmallnuclearreactor.
facilitiesareavailableforclinicaltrials,sinceall
Thetherapeuticef icacyofneutronbeamfor
these facilities are currently based on a nuclear
the proposed BNCT facility were calculated
reactor source. In order to ind an alternative
through its FOM, i.e. Dose Rate (ADDR),
source for BNCT applications a DT neutron
Treatment Time (TT), Advantage Depth (AD),
generator has been considered, using the
Advantage Ratio (AR) and Therapeutic Depth
MCNP4B Monte Carlo code. The proposed
(TD). ADDR is de ined as the maximum delivfacility is optimized in terms of the moderator
ereddoseratetohealthytissue.Bearinginmind
andbeam iltering. 7LiFincorporatingatruncatthatthemaximumallowabledosetothehealthy
ed-cone-shaped made of D2O and TiF3 were
tissueis12.5Gy(19),theTTcanbeestimated.AD
chosen
as the moderator materials. The use of
indicatesthedepthintissueatwhichthedoseto
60
Niasfastneutron ilter,Cdasthermalneutron
the tumor equals the maximum dose to the
ilterandBiasgamma ilterhasledtoimproving
healthytissue.ARistheintegraldosethatwould
the qualityof the beamfor BNCT.The resulting
be delivered to tumor tissue, uniformly
doseoftheradiationemittedfromthefacilityis
distributed within the brain, divided by the
evaluatedde iningtheFOMinphantom.Accordintegral dose delivered to normal tissue, while
ingtotheresultsobtained,theproposedfacility
TD de ines the depth at which the tumor dose
meetsalltherecommendedbyIAEAparameters
falls below twice the maximum dose to healthy
and constitutes an attractive alternative to the
brain(11,20-22).
nuclearreactors.
The in-phantom parameters of the proposed
facilityandfromsomepreviouspublishedstudCon lictofinterest:Declarednone
iesarelistedintable5andshowaneutronbeam
Table 5. In-phantom parameters evaluated for the proposed designed BSA and some other facili es.
Facility
ADDR (cGy/min) TT (min) AD (cm)
Proposed facility
THOR
(25)
FiR 1
(25)
R2-0
(25)
Kononov et al., 2004
FCB MIT
RA-6
(27)
(28)
Rasouli et al.
(11)
Rasouli and Masoudi
23
(26)
(10)
TD (cm)
AR
63.29
19.75
5.94
4.34
2.86
50
25
8.9
5.6
-
45
30
9
5.8
-
67
20
9.7
5.6
-
100
12.5
9.1
-
-
55
22.72
9.9
-
5.7
16.25
76.92
6.8
-
2.8
41.3
30.2
9.4
7
-
50.35
24.8
8
5.89
4.26
Int. J. Radiat. Res., Vol. 13 No. 1, January 2015
Downloaded from ijrr.com at 16:04 +0430 on Saturday June 17th 2017
[ DOI: 10.7508/ijrr.2015.01.002 ]
Fantidis and Antoniadis / Optimization study for BNCT facility based on a DT neutron generator
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