Eleventh World Congress on Neutron Capture TherapyTuesday, October 12, 2004 - PMParallel Session 4 - N u c l ea r E n g i n e e r i n g a n d P hy s i c s4:15 PM -Characteristics of the new THOR epithermal neutronbeam for BNCT. C.J. Tung a, *, Y.L. Wang a , F.Y. Hsu b , S.L. Chang a ,Y-W.H. Liu ca Department of Nuclear Science, National Tsing Hua University, Hsinchu 300, Taiwan,b Department of Radiological Technology, Yuanpei University of Science andTechnology, Hsinchu, Taiwan, c Department of Engineering and System Science,National Tsing Hua University, Hsinchu, TaiwanA characterization of the new Tsing Hua Open-pool Reactor (THOR) epithermal neutronbeam and an evaluation of its boron neutron capture therapy (BNCT) performancewere studied using Monte Carlo calculations and the treatment planning system (TPS).The beam facility is currently under construction and expected in completion in March2004. It will be used for a full spectrum study in BNCT leading to possible clinical trials.This report discusses the characteristics of the new THOR beam in air, a referencehead phantom, and a patient treated in the Harvard-MIT clinical trial.The epithermal neutron flux for 1 MW THOR power calculated using TORT and MCNP4C codes is 1.7 x 109 n cm-2 s-1 in air at the beam exit, accompanied by photon andfast neutron absorbed dose rates of 0.21 and 0.47 mGy s-1, respectively. The depthprofiles for the individual dose components in a modified Synder head phantom werecalculated using the MCNP 4C code for clinical boron concentrations. These profileswere then used to determine the figures of merit, or the advantage parameters. With10B concentrations in normal tissue and tumor of 11.4 and 40 ppm, the calculatedadvantage depth dose rate is 0.53 RBE-Gy min-1 at the advantage depth of 85 mm,giving an advantage ratio of 4.8. Applying the same irradiation geometry and prescriptiondose as those adopted in the Harvard-MIT clinical trial, i.e. three fields with a totalof 12.9 RBE-Gy maximum biologically weighted normal tissue dose, the dose patternsfor a patient were derived from the NCTPlan TPS using the new THOR beam andcompared with results of the MITR-II M67 beam. The THOR beam yielded a tumordose ranging from 33.4 to 72.7 RBE-Gy (or 0.91 to 1.98 RBE-Gy min-1 in dose rate)as compared to 16.5 to 38.0 RBE-Gy (or 0.047 to 0.109 RBE-Gy min-1) for the MITR-IIM67 beam. Corresponding brain tissue dose extends from 0.39 to 12.9 RBE-Gy for theTHOR beam as compared to 0.39 to 10.8 RBE-Gy for the MITR-II M67 beam. The totalirradiation time of all three fields for the THOR beam is 36.7 minutes.The in air characteristics of the new THOR beam meet most of the criteria set by theInternational Atomic Energy Agency for desired neutron beam parameters for BNCT.The phantom characteristics of this beam provide advantage parameters showing thateven the deepest seated brain tumors can be treated with the required therapeuticdoses to the tumor and normal tissues. Further, the application of the NCTPlan TPSrevealed that the new THOR beam yielded a much larger dose to the tumor and somewhatlarger dose to the tissue than the MITR-II M67 beam. The present study confirmsthe suitability of the new THOR beam for possible BNCT clinical trials.4:35 PM -Depth-dose evaluation for osteosarcoma and prostatecancer treatments using an epithermal neutron beam.Tetsuo Matsumoto, Hiroshi Nakata and Kazuo AkutsuAtomic Energy Research Lab., Musashi Institute of Technology, Ozenji 971, Asao-ku,Kawasaki-shi, 2150013 JapanFor boron neutron capture therapy (BNCT) to enjoy the same recognition as conventionalradiotherapy, it should be applied to treat not only brain tumors but also variouscancers. An epithermal neutron beam could be now expected to apply for a deep andwidespread tumor. We reported the depth-dose distributions for liver, lung and pancreascancer treatments by BNCT at last symposiums1, 2. The present communicationcovers calculation of depth-dose distributions using an epithermal neutron beamfor possible treatment of both osteosarcoma and prostatic cancers. The osteosarcomais generally attacked in the growth, and is a metastasis cancer having strong radiationresidence. The prostatic cancer is attacked in the older, but is recently increasing inJapan.The osteosarcoma (3x3x3 cm3) is modeled around the knee (8x8x15.5 cm3) includingFemur, Patella and Medical meniscus. The prostatic cancer (1x1x1 cm3) is modeledinside the prostate (3x3x3 cm3) around the generative organs. Rectum (6x4x8 cm3),Bladder (8x10x5 cm3) and Testicle (1x1.5x5 cm3) are also included in the model.The calculations were performed by the three-dimensional continuous-energy MonteCarlo code MCNP. The epithermal neutron beam from a TRIGA-II reactor was usedas a primary neutron source for the depth-dose calculation. The 10B concentrationsin the tumor and normal tissue were assumed at 30 ppm and 3 ppm, respectively. Thephysical dose without considering RBE value was calculated for the estimation of thedepth-dose distributions by MCNP.The calculations showed that the average physical dose in the osteosarcoma was 16Gy/h and the dose ratio of tumor to normal tissue was 4.8 when attaining an epithermalneutron flux of 1.5x109 ncm-2s-1. The average physical dose in the prostatic cancerwas 14 Gy/h and the dose ratio of tumor to normal tissue was about 2.2. The doseevaluation suggests that BNCT could be applied for both osteosarcoma and prostaticcancer treatments.1. Tetsuo Matsumoto: 2001. Depth-dose evaluation for liver cancer treatment by BNCTand GdNCT using an epithermal neutron beam. Frontiers in Neutron Capture Therapy,edited by Hawthorne, pp.1351-1356, New York2. Tetsuo Matsumoto and Fuji Fukushima: 2000. Depth-dose evaluation for lung andpancreas cancer treatment by BNCT using an epithermal neutron beam. Program &Abstracts in 9th international Symposium on Neutron Capture Therapy for Cancer,pp.133-134, Osaka, Japan4:55 PM -In-phantom imaging of all dose components in boronneutron capture therapy by means of gel dosimeters.G. Gambarini a,b, *, V. Colli a,b , S. Gay a,b , C. Petrovich c , L. Pirola a , G. Rosi da Dipartimento di Fisica, Universita degli studi di Milano, via Celoria 16, 20133 Milano,Italy, b INFN, National Institute of Nuclear Physics, Bologna, Italy, c FIS-NUC, ENEA,Bologna, Italy, d FIS-ION, ENEA, Casaccia, Rome, ItalyThe experimental method for in-phantom imaging and profiling the absorbed dose inNCT, separating the contributions of the various secondary radiation components, hasbeen improved. The method is based on suitably designed gel dosimeters in form oflayers (thickness 1-3 mm) and the discrimination of dose components is achieved bymeans of pixel-to-pixel manipulations of images obtained with gel-dosimeters havingdifferent isotopic composition. Gel dosimeters are aqueous systems and their compositionscan be conveniently adjusted so that in neutron fields the absorbed dose dueto each secondary radiation is really almost the same as that absorbed by tissue. Inthe studied dosimeter (Fricke-XylenolOrange infused gel), ionising radiation causeschanges of the optical absorption of visible light. From the optical transmittance images,detected using a CCD camera, dose images are obtained. The method for separatingdose contributions is that of introducing, in the phantom of interest, coupledlayers of gel dosimeters both having good tissue-equivalence for neutron secondariesbut with a composition differing for the content of one isotope whose reactions withneutrons give production of charged particles.In gel with standard composition, the absorbed dose in neutron fields is the sum ofthe gamma dose due to background and to the reactions 1H(n,gamma)2H and thefast neutron dose, mainly due to recoil protons. In a gel with identical composition butadded with 10B, the absorbed dose is the sum of the mentioned contributions plusthe therapy dose. If nitrogen is added, in the same way, the dose due to the protonsemitted in the reaction 14N(n,p)14C contributes to the total. By means of suitablemanipulations of images, the various dose contributions can be obtained. Gammaand recoil-proton contributions can be separated too, by elaborating the absorbeddoses in standard gel and in gel made with heavy water. Proper software has beendeveloped for the pixel-to-pixel manipulation of images. The software has been implemented,in order to operate all the algorithms that are necessary for obtaining, fromthe GL images of couples of gel dosimeters having different compositions, the imagesof the various dose components. Manipulation algorithms include parameters like thecalibration coefficients of the specific gel dosimeters and the dependence of their sensitivityon the radiation LET.Large dose images are obtainable with this method, because the layer geometry ofdosimeters avoids sensible variation of neutron transport due to the isotopic compositionof gel. It is important to observe that the peculiarity of the method is not in the kindof used gel dosimeter or of imaging technique (that is optical or magnetic resonanceanalysis). Fricke-XylenolOrange-infused gels have been chosen because it is particularlysimple to prepare gel matrixes with different isotopic composition and moreoverthe used chemical compounds and the resulting gel are not toxic for the operator. However,whichever kind of gel dosimeter and analysis would be adequate, provided thatthe dosimeters do not change neutron transport, and this is true for layer geometry.5:15 PM -Experimental and computational validation of BDTPSusing a heterogeneous boron phantom. G.G. Daquino a, *, N.Cerullo b , M. Mazzini b , R.L. Moss c , L. Muzi ba CERN, PH/SFT, J00200, CH-1211, Geneva 23, Switzerland, b DIMNP, Universityof Pisa, Via Diotisalvi 2, 56126 Pisa, Italy, c JRC, European Commission, PO Box 2,Westerduinweg 3, Petten, The NetherlandsIntroduction: The idea to couple the Treatment Planning System (TPS) to the informationon the real boron distribution in the patient acquired by Positron Emission Tomography(PET) is the main added value of the new methodology set-up at DIMNP of Universityof Pisa, in collaboration with the JRC of Petten (NL). Building on the CARONTEexperience (Cerullo et al., 1998), this methodology has been implemented in a new34
Eleventh World Congress on Neutron Capture TherapyTuesday, October 12, 2004 - PMParallel Session 4 - N u c l ea r E n g i n e e r i n g a n d P hy s i c sTPS named BDTPS (Boron Distribution Treatment Planning System).Materials and methods: BDTPS is an integrated system, which makes use of theMCNP code (Briesmeister, 2000). Besides the “standard” features included in all treatmentplanning systems, BDTPS implements a software architecture based on threestrictly dependent models, named the 3D, the Monte Carlo (MC) and the Boron (B)models. The 3D model is constructed through a stack of CT images of the patient’sorgan and serves as reference for the automatic reconstruction of the MC model. TheB model is built on the basis of a co-registered stack of PET images.The test and validation of BDTPS required the use of an ad hoc phantom namedHEBOM (HEterogeneous BOron phantoM). HEBOM’s structure, comprising severalPMMA slabs, was conceived to host both the instrumentation for neutron fluence anddose measurement and 64 vials, which were filled with solutions containing boron indifferent concentrations to mimic a highly heterogeneous distribution of this element.P/N diodes were used for measuring the thermal neutron fluence, while paired Ar/Mgand TE/TE ionization chambers measured the fast neutron fluence and the gammadose. The experimental validation was integrated with computational tests made usingboth SERA and MCNP-4C3.Discussion: Some discrepancies appeared in the comparison between the BDTPS andSERA results, but reasonable agreement was found between the results of BDTPSand the analytical model in all HEBOM layers and for all the measured parameters (borondose, thermal neutron flux, proton recoil dose, total gamma dose). This highlightedin particular the difficulty for a “standard” TPS to follow the boron dose distribution witha heterogeneous boron distribution in the tissues.Conclusions: This work demonstrated the correct operation of BDTPS by means ofmeasurements and reference calculations. BDTPS version 1.0 is currently the onlyintegrated TPS package able to evaluate the boron dose on the basis of the realmacroscopic boron distribution acquired through PET scanning. Hopefully, this newtool will be applied and further validated in the Italian BNCT research project (Cerulloet al., 2002).35
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