Leung, K. N.

Verbeke, J. M.

Vujic, J.

UNT Digital Library

INVESTIGATION OF2H(d; n)3He AND3H(d; n)4HeFUSION REACTIONS AS ALTERNATIVE NEUTRONSOURCES FOR BNCT.J.M. Verbekea;b, J. Vujicaand K.N. LeungbaNuclear Engineering Department, University of California, BerkeleybLawrence Berkeley National LaboratoryBerkeley, CA 94720AbstractBeam-shaping assemblies have been designed to moderate high energy neutrons from the fusionreactions2H(d; n)3He (DD) and3H(d;n)4He (DT) for use in Boron Neutron Capture Therapy. Thelow yield of DD is an obstacle for the treatment of Glioblastoma Multiforme. Our analysis shows thatthe high-energy neutrons from DT can be moderated to epithermal energy range without reducingthe neutron ux to a negligible level. With the optimal beam-shaping assembly design for DT, a 1 Adeuteron beam with energy of 120 keV leads to a treatment time of 50 minutes. The dose near thecenter of the brain obtained with this conguration is about 50% higher than the dose from a typicalspectrum produced by the Brookhaven Medical Research Reactor (BMRR), and is comparable to thedose obtained by other accelerator-produced neutron beams.1 INTRODUCTIONThe main goal in this study is to identify some alternative accelerator-based reactions that could result ina simple and inexpensive accelerator and target system while satisfying all of the requirements for boronneutron capture therapy (BNCT).The need for epithermal neutron beams with energy distribution peaking around 10 keV [1, 2]led dierent groups to investigate reactor- and accelerator-based neutron sources. Reactions such as7Li(p; n),9Be(p; n) and9Be(d; n) are currently being investigated as accelerator-based neutron sourcesfor BNCT because the energy of neutrons is of the order of hundreds of keV [2, 3, 4]. The drawback ofthese reactions is the high energy of the protons and deuterons required, which varies usually between2.3 and 4.0 MeV depending on the reaction, requiring a large accelerator and treatment facility.To the best of authors knowledge, the reactions2H(d; n)3He (DD) and3H(d; n)4He (DT) havenot been investigated so far for BNCT, because of the high energy of the neutrons produced, 2.43 and 14.1MeV respectively. Provided these neutrons can be moderated to therapeutically useful regions withoutlarge losses, the high neutron yields for relatively low deuteron beam energy (100-200 keV) is a deniteadvantage over other accelerator-based neutron sources. A 120 keV deuteron beam yields approximately3:71011n=sec=A and 1014n=sec=A for DD and DT respectively [5]. This paper investigates the feasibilityof generating neutrons for BNCT using the DD and DT reactions. It focuses on two points: designing amoderator to decrease neutron energies to epithermal regions and determining the dose distribution in ahead phantom. Monte-Carlo codes are used for both tasks.2 NEUTRON BEAM-SHAPING ASSEMBLY (BSA)In order to obtain a therapeutically useful epithermal neutron beam, the BSA needs to be optimized.The neutron transport through the BSA is simulated using the Monte-Carlo code MCNP [6]. Aftermoderation, a second Monte-Carlo code BNCT RTPE [7] is used to calculate the dose distribution in ahead phantom.The neutron source is characterized as follows. Monoenergetic neutrons are emitted isotropicallyand uniformly from a 5 cm-diameter spotsize on a 40 cm-diameter target. Source neutrons enter acylindrical BSA with a monoenergetic energy distribution. They travel through the cylinder composedof several layers of dierent materials until they reach the other side where the patient is located.An accepted gure-of-merit used to measure the neutron beam quality is the dose equivalent tothe tumor at the centerline of the brain, and it is based on biological criteria. The tumor dose at aFigure 1: Beam-shaping assembly (BSA).depth of 8 cm is used as a gure-of-merit in our study. This dose is limited by Brookhaven NationalLaboratory's (BNL) clinical trial protocol [8] which suggests that the local equivalent dose to the healthytissues must not exceed 12.5 Gy. The treatment time will thus be limited by this value.For the dose computation with BNCT RTPE [7], concentrations of 13g=g of10B in healthytissues and 45:5g=g of10B in tumor are used. The individual dose components (boron dose, gammadose, nitro-dose and fast dose) are combined to yield estimates of total doses per neutron to healthytissue and tumor, using the following equation:Dtotal= CF DB+RBENDN+RBErDr+RBEDwhere the following assumptions are made: the normal tissue and tumor compound factors CFare 1.3 and 3.8, respectively; proton-recoil reactions RBEr: 3.2; nitrogen capture reaction RBEN: 3.2;RBE: 1.0. The10B concentrations, compound factors and RBE factors were taken from values used inBNL's protocol [8].2.1 Optimal BSA and dose distribution for DDThe optimal combination of materials that we came up with for DD was 30 cm of7LiF and 18 cm of40%Al/60%AlF3. The BSA is 25 cm in diameter and surrounded by a thin (0.5 mm) layer of6LiF anda thick 30 cm Al2O3reector. A detailed description of the geometry can be found in Ref. [9]. The10-8 10-7 10-6 10-5 10-4 0.001 0.01 0.1 1. 10.Energy [MeV]0.1.2.3.4.5.6.7.e-4tally/particle.024681012140 2 4 6 8 10 12 14 16Equivalent dose [RBE*Gy]Depth [cm]Total doseBoron doseGamma doseNitro doseFast dose(a) (b)Figure 2: (a) Neutron energy distribution after moderation and (b) total dose to the healthy tissues withthe dierent dose components in the head phantom.neutron spectrum after moderation and the equivalent doses to the healthy tissues (with its components)are shown in Fig. 2. The equivalent tumor dose to the desired depth of 8 cm with this moderation is18 Gy-Eq. The equivalent skin dose is 8.9 Gy-Eq. Accounting for the neutron yield of DD | whichis 8:5  109n=sec=mA for a 400 keV beam [10] | this moderation would lead to a treatment time of840 hours for a 5 mA deuteron beam. Even with a 1 A deuteron beam, the treatment time would bemore than 4 hours. This unacceptably large treatment time could potentially be reduced by using severalbeams, by increasing the beam intensity, or by improving the beam shaping assembly.2.2 Optimal BSA and dose distribution for DTA few simulations for dierent combinations of materials showed that all neutrons above 1 MeV contributenot only to the fast dose at the surface of the brain, but also to the fast dose throughout the head, includingthe point of maximum tissue dose which limits the treatment time. The BSA optimization emphasis wasthus on decreasing the high energy neutron ux to a level as low as possible.The best BSA design we came up with was composed of thick layers of bismuth, iron, 40%Al/60%AlF3,and of thin layers of6LiF and lead. The BSA is surrounded by a 20 cm thick lead reector. The largecross-sections of bismuth and lead for (n,2n) reactions are used benecially to compensate for the neutronlosses by leakage and absorption during the moderation. Iron is used to reduce the fast neutron energiesfrom 14 MeV to around 1 MeV. The mixture 40%Al/60%AlF3is interesting in the sense that the elasticscattering resonances of aluminum supplement exactly the ones of uorine from 27 keV up to the highenergy tail, except for a narrow energy range around 70 keV. This resonance structure will preferentiallyreduce the number of neutrons above 27 keV. Lithium uoride and lead are nally used to reduce thethermal neutron ux and to decrease the photon ux respectively at the end of the moderator.10-7 10-6 10-5 10-4 0.001 0.01 0.1 1. 10. 100.Energy [MeV]0.1.2.3.4.5.6.7.e-4tally/particle.024681012140 2 4 6 8 10 12 14 16Dose [Gy]Depth [cm]total tissue doseboron dosegamma dosenitro dosefast dose(a) (b)Figure 3: (a) Neutron energy distribution after moderation and (b) total dose to the healthy tissues withthe dierent dose components in the head phantom.The neutron spectrum after moderation and the components of the doses to the healthy tissuesare shown in Fig. 3. With this moderation, the equivalent tumor dose in the head phantom at 8 cmdepth is 21.9 Gy-Eq and the equivalent dose to the skin is 9.6 Gy-Eq. With a 120 keV deuteron beam,a 1 A deuteron beam intensity would lead to a treatment time of 50 minutes.2.3 Summary and comparison with other neutron sourcesTable 1 summarizes the main characteristics of the tumor dose distribution for DD, DT and other neutronsources proposed or used for BNCT. The optimized spectrum from the DT neutron source produces about50% higher dose near the center of the brain than the currently used reactor spectrum at BMRR.3 CONCLUSIONSTwo fusion reactions (DD and DT) have been studied as possible neutron sources for BNCT. The lowneutron yield of the DD reaction is an obstacle for its use in this particular therapy. Neutrons from theNeutron source3H(d; n)4He2H(d; n)3He7Li(p; n)7Be7Li(p; n)7Be BMRRModerator Bi=Fe7LiF7LiF Al=AlF3(Al2O3)Al=AlF3Al=AlF3[2] [2] [11]Proton energy [MeV] 0.12 0.4 2.3 2.4 -Proton current [mA] 1000 5000 20 20 (3 MW)Treatment time [min] 50 50 40 54 39Equ. tumor dose (max) [Gy-Eq] 64.8 60.1 64.3 65.1 61.6Equ. tumor dose (5 cm) [Gy-Eq] 51.8 42.9 50.5 51.4 38.6Equ. tumor dose (8 cm) [Gy-Eq] 21.9 18.0 21.4 22.3 14.5Advantage depth [cm] 9.5 9.0 9.5 9.5 8.4Table 1: Comparison of treatment characteristics for dierent neutron sources.DT reaction could be moderated to around 10 keV without reducing the neutron ux to a negligiblelevel. An equivalent tumor dose of 21.9 Gy-Eq could be achieved at a depth of 8 cm in the head pantom,which is about 50% higher than doses obtained by a neutron beam currently used at BMRR for clinicaltrials. For a treatment time of 50 minutes, the deuteron beam requirements are 120 keV and 1 A. Takingadvantage of the small sizes of the ion sources and accelerators, several beams could easily be used inparallel and treatment times could be reduced to a fraction of an hour.4 ACKNOWLEDGEMENTSThis work is partly supported by the US Department of Energy under contract number DE-AC03-76SF00098.References[1] J.C. Yanch, X-L. Zhou, and G.L. Brownell, "A Monte Carlo Investigation of the Dosimetric Properties ofMonoenergetic Neutron Beams for Boron Neutron Capture Therapy", Radiation Research 126, 1-20 1991[2] D.L. Bleuel, R.J. Donahue, B.A. Ludewigt, and J. Vujic, "Designing Accelerator-Based Epithermal NeutronBeams for BNCT", Medical Physics, 25 (9), 1725-1734, 1998.[3] C.K.C. Wang, T.E. Blue, R. Gahbauer, "A Neutronics Study of an Accelerator-Based Neutron IrradiationFacility for BNCT", Nuclear Technology 84, 93-107, 1989[4] Y.C. Yanch, X.L. Zhou, R.E. Shefer, R.A. Klinkowstein, "Accelerator-Based Epithermal Neutron BeamDesign for Neutron Capture Therapy", Med. Phys., 19, 709-721, 1992[5] L.A. Shope, "Theoretical thick target yields for the D-D, D-T, and T-D nuclear reactions using the metaloccluders Ti and Er and energies up to 300 keV", SC-TM-66-247, Sandia Laboratory, Albuquerque, July1966[6] "MCNP-A A General Monte Carlo N-Particle Transport Code, Version 4B", J.F. Briesmeister, Ed., LA-12625-M, Los Alamos National Laboratory, 1997.[7] D. Nigg, "Methods for Radiation Dose Analysis and Treatment Planning in BNCT", Int. J. of Rad. Onc.Bio. Phy. 28, 1121-1134, 1994.[8] A.D. Chanana, "Boron Neutron Capture Therapy of Glioblastoma Multiforme at the Brookhaven MedicalResearch Reactor, A Phase I/II Study, FDA IND #43317, Protocol #4", Medical Department, BrookhavenNational Laboratory, Upton, NY 11973, January 1996[9] J.M. Verbeke, S.V. Costes, D.Bleuel, J. Vujic, and K.N. Leung, "Designing an Epithermal Neutron Beam forBNCT for the Fusion Reactions2H(d;n)3He and3H(d; n)4He", proceedings of the International Conferenceon the Physics of Nuclear Science and Technology, Long Island, NY, October 5-8, 1998[10] High Voltage Engineering Corporation, Burlington, Massachusetts.[11] J.A. Coderre, R. Bergland, J. Capala, M. Chadha, A.J. Chanana, E. Elowitz, D.D. Joel, H.B. Liu, and D.Slatkin, "Boron Neutron Capture Therapy for glioblastoma multiforme using p-boronophenylalanine andepithermal neutrons { Trial design and early clinical results", J. Neuro-Oncol. 33, 93-104 1997.

Investigation of 2H(d,n)3He and 3H(d,n)4He Fusion Reactions asAlternative Neutron Sources for BNCT

Verbeke, J.M.

Leung, K.N.

eScholarship - University of California

Investigation of 2H(d,n)3He and 3H(d,n)4He Fusion Reactions as Alternative Neutron Sources 
for BNCT

https://escholarship.org/uc/item/2fw5x01n

Investigation of 2H(d,n)3He and 3H(d,n)4He Fusion Reactions asAlternative Neutron Sources for BNCT

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