Abstract ID: 122 Verification of dose estimation for Monte-Carlo based treatment planning system for boron neutron capture therapy

Abstracts / Physica Medica 42 (2017) 1–50

CT are expected to improve the accuracy of quantitative imaging for radiotherapy.

References 1. 2. 3. 4.

De Man B. IEEE Trans 2000;20(10). Cai C. Med Phys 2013;40(11). Ali ESM, Rogers DWO. Phys Med Biol 2011;57(1). Zhao W. Phys Med Biol 2014;60(1).

http://dx.doi.org/10.1016/j.ejmp.2017.09.062

Abstract ID: 116 Comparison of beam output factors in MCNP6 and Geant4 based IAEA phase-space files Raquel Ivon Sanchez-Estrada a,*, Enrique Betancourt Garcia a, Arturo Delfin Loya b, Edmundo del Valle Gallegos b a School of Physics and Mathematics, Nuclear Engineering Department, Mexico City, Mexico b National Institute for Nuclear Research, Nuclear Systems Department, Mexico City, Mexico ⇑ Presenting author.

Monte Carlo (MC) dose calculation algorithms demand an accurate characterization of the radiation beam. At present, three MCbased beam models are commonly used for dose calculation; namely, full MC simulation, virtual source model, and phase space (phsp) files. The first two require detailed information of the LINAC head: information that is not always available from vendors. Therefore, properly validated phase-space data for external beam radiotherapy, available from the IAEA Nuclear Data Services section, remains a valuable alternative for MC beam simulation. The aim of this work is to compare the beam output factors obtained by MCbased phsp simulations in MCNP6 and Geant4. The simulations were performed with the photon mode energies of 6, 10, and 25 MV on the ELEKTA Precise. The simulations are divided into two steps: (1) the development of a method for directly reading the phase-space files provided by the IAEA in MCNP6, and (2) the determination of cutoff values, variation reduction techniques, and field size. Patientspecific beam line devices (blocks, jaws, wedges, etc.) were not simulated. The comparison of the output factors as percentage depth dose (PDD), lateral dose profiles, and dose distributions for different field sizes were computed using Geant4 and MCNP6. Both calculations generate matching PDD for a range of open-field sizes within the statistical uncertainties. Variation in lateral dose profiles varies up to 5% in the 25 MV energy mode. Comparison of dose distributions for an open 10  10 field by the gamma evaluation test returns a value of 0.93. Despite the lack of a user-friendly MCNP6 interface, this work shows that MCNP6 is suitable for beam simulation based IAEA-phsp. http://dx.doi.org/10.1016/j.ejmp.2017.09.063

Abstract ID: 118 Internal dosimetry of 68Ga-DOTATATE using Monte Carlo GATE simulation for XCAT phantom Mersede Mokri a, Mohmmad Reza Ay b, Sima Taghizade c, Marzieh Ebrahimi a, Parham Geramifar a a

Research Center For Nuclear Medicine, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran b Medical Physics and Biomedical Engineering Department, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran c Research Center for Science and Technology in Medicine, RCSTM, Tehran, Iran

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Introduction. Widespread use of FDG PET/CT imaging leads to improvement in non-FDG- avid somatostatin receptor imaging of tumor tissue. These synthetic somatostatin analogs can be labeled with b-emitting radionuclides, such as 68Ga[1], but estimating the absorbed dose in critical organs is important. The aim of this research is to calculate absorbed dose in all organs especially pituitary gland and thymus in 68 Ga-DOTATATE dosimetry. Materials and Methods. Two total body male and female XCAT phantoms with 128128 matrix size and 600 slices containing 1 mCi activity of 68Ga was simulated. GATE Monte-Carlo code was employed for dosimetry calculations. Based on MIRD schema, we reported s-values of self-absorption and cross-irradiation in spleen, bladder, kidneys and liver, as well as cross-irradiation in pituitary gland and thymus. Results. We reported the S-value for spleen, the most critical organ in 68Ga-DOTATATE to be 13.7e 004 mGy/MBq-s and 15.6e 004 mGy/MBq-s in male and female phantom respectively. The highest amount of cross-irradiation in spleen is from kidney with the amount of 0.097e 004 mGy/MBq-s. The amount of self-absorption is in Bladder with 42.1e 004 mGy/MBq-s and 50e 004 mGy/MBqs in male and female phantom respectively. The absorbed dose in thymus from spleen is 2.3710e 006 mGy/MBq-s in male and 3.1138e 006 mGy/MBq-s in female. Absorbed dose of pituitary gland from spleen is 0.53e 007 mGy/MBq-s. Conclusion. We performed internal dosimetry using XCAT phantoms and GATE Monte-Carlo code for 68Ga. Our results could be helpful in estimating absorbed dose in critical organs specially those not being considered in conventional methods.

References 1. Skoura E et al. The impact of 68Ga-DOTATATE PET/CT imaging on management of patients with neuroendocrine tumors: experience from a national referral center in the United Kingdom. J Nucl Med 2016;57(1):34–40. http://dx.doi.org/10.1016/j.ejmp.2017.09.064

Abstract ID: 122 Verification of dose estimation for Monte-Carlo based treatment planning system for boron neutron capture therapy Hiroaki Kumada a,*, Kenta Takada b, Teruhito Aihara a, Akira Matsumura a, Hideyuki Sakurai a, Takeji Sakae a a

University of Tsukuba, Faculty of Medicine, Tsukuba, Japan University of Tsukuba Hospital, Proton Medical Research Center, Tsukuba, Japan ⇑ Presenting author. b

University of Tsukuba is developing a treatment device for accelerator-based for boron neutron capture therapy (BNCT). In the project, not only the treatment device (neutron source) but also several peripheral devices requiring in BNCT treatment [1]. As part of the development, a Monte-Carlo based treatment planning system (Developing code: Tsukuba-Plan) applicable to BNCT is also being developed. Regarding Monte-Carlo dose calculation engine, the Tsukuba-Plan has employed PHITS as the multi-purpose Monte Carlo Particle and Heavy Ion Transport code System. PHITS allows to calculate behaviors for several radiations such as neutrons, photons, protons and heavy-ions [2]. Therefore the Tsukuba-Plan with PHITS enables to perform dose estimation for not only BNCT but also particle radiotherapy and X-ray therapy. A prototype of the Tsukuba plan has been completed. At present, we are carrying out several verifications for the Tsukuba-Plan.

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Abstracts / Physica Medica 42 (2017) 1–50

To verify dose estimation accuracy of the system, some experiments with a water phantom were simulated by using the Tsukuba-Plan, and the calculation results were compared with experimental data. In the experiments, gold foils and TLDs were set in the phantom, and then the phantom was set to in front of the beam aperture of the neutron source for BNCT device. Neutron beam was irradiated to the phantom, finally two-dimensional distributions for thermal neutron flux and gamma-ray dose in the phantom were measured. On the other hand, regarding simulation of the experiments with the Tsukuba-Plan, CT images of the water phantom were loaded to Tsukuba-Plan, and the irradiation conditions were represented. And calculations of two-dimensional distributions for both of thermal neutron flux and gamma-ray dose in the phantom were determined by using PHITS. The calculation results obtained from the Tsukuba-Plan were compared with the experimental values. The calculation values were in good agreement with the experimental values within statistical errors and experimental errors. The verification results demonstrated that Tsukuba-Plan enables to perform dose estimation for BNCT. Clinical group of University of Tsukuba plans to perform clinical trial for BNCT by using the neutron source for BNCT treatment device in the near future. Tsukuba-Plan will be applied to the clinical trials in practical use.

References

Regarding proton therapy, we have constructed 155 MeV and 200 MeV proton beam source and a geometry struction data for the proton therapy device installed in our Hospital. Verification for calculation accuracy for proton irradiation were performed. Phantom experiments performed using the proton therapy device in advance were represented by the Tsukuba-Plan. The proton dose distributions in the phantom were determined, and the calculations were compared with the experimental values. Calculations for both of proton therapy and X-ray therapy were in good agreement with experimental values, respectively. The results demonstrated that the Tsukuba-Plan enables to estimate accurately doses for proton irradiation and X-ray irradiations. To put TsukubaPlan to practical use for proton therapy and X-ray therapy, TsukubaPlan is improved further and several verifications are performed. This work was supported by JSPS KAKENHI Grant Nos. JP16K15343.

References 1. Kumada H, Matsumura A. Project for the development of the linac based NCT facility in University of Tsukuba in University of Tsukuba. Appl Radiat Isot 2014;88:211–5. 2. Iwase H, Niita K, Nakamura T. Development of general-purpose particle and heavy ion transport Monte Carlo code. J Nucl Sci Technol 2002;39:1142–51. http://dx.doi.org/10.1016/j.ejmp.2017.09.066

1. Kumada H, Matsumura A. Project for the development of the linac based NCT facility in University of Tsukuba. Appl Radiat Isot 2014;88:211–5. 2. Iwase H, Niita K, Nakamura T. Development of general-purpose particle and heavy ion transport Monte Carlo code. J Nucl Sci Technol 2002;39:1142–51. http://dx.doi.org/10.1016/j.ejmp.2017.09.065

Abstract ID: 124 Application expansion of the Monte-Carlo based treatment planning system for BNCT to particle radiotherapy and X-ray therapy Hiroaki Kumada a,*, Kenta Takada b, Teruhito Aihara a, Akira Matsumura a, Hideyuki Sakurai a, Takeji Sakae a

Abstract ID: 125 Fundamental study for practical application of radiotherapy treatment planning system capable of evaluating neutron dose generated by various radiotherapy beams Kenta Takada a,b,*, Hiroaki Kumada a,b, Junichi Kouketsu a, Syouya Tobita c, Toshiyuki Terunuma a,b, Hideyuki Sakurai a,b, Takeji Sakae a,b a University of Tsukuba Hospital, Proton Beam Therapy Center, Tsukuba, Japan b University of Tsukuba, Faculty of Medicine, Tsukuba, Japan c University of Tsukuba, Graduate School of Comprehensive Human Sciences, Tsukuba, Japan ⇑ Presenting author.

a

University of Tsukuba, Faculty of Medicine, Tsukuba, Japan University of Tsukuba Hospital, Proton Medical Research Center, Tsukuba, Japan ⇑ Presenting author. b

University of Tsukuba is developing an accelerator-based treatment device for boron neutron capture therapy (BNCT). As part of the development, a Monte-Carlo based treatment planning system (developing code: Tsukuba-Plan) is being developed [1]. The Tsukuba-plan has employed PHITS as the Monte-Carlo transport calculation code [2]. PHITS can calculate neutron, photon as well as proton and heavy-ions including carbon-ions. Therefore, Tsukuba-Plan with PHITS enables to perform dose estimations for not only BNCT but also particle radiotherapy and X-ray therapy. In BNCT protocols for malignant brain tumor, X-ray therapy is added after BNCT to enhance the treatment effect. And in the future, proton therapy will be also applied in stead of the X-ray therapy in order to improve therapeutic dose distribution. Therefore, the treatment planning system is required dose estimation for the combined multi-modality therapy. Based on this background, the aim of this study is to expand application field of the Tsukuba-plan to conventional external radiotherapies. University of Tsukuba Hospital has X-ray therapy, proton therapy and BNCT. Thus, first, we have expanded Tsukuba-plan to proton therapy and X-ray therapy.

There are many papers focused on secondary neutrons by calculation or measurement in high-energy radiotherapy fields [1,2]. Monte Carlo calculation is easy to acquire the three-dimensional spatial distribution of the neutrons and is considered to be particularly useful tool for evaluating the ‘‘on-axis” of the primary radiotherapy beam. In this study, calculations were performed for practical application of treatment planning that can take threedimensional neutron dose into account by combining with new treatment planning system ‘‘Tsukuba-Plan” currently developed by University of Tsukuba. The incident radiotherapy beams were Xrays and ‘‘passive” particle beams (proton beam, carbon-ion beam). Particle and Heavy Ion Transport code System (PHITS) [3] was used as Monte Carlo code. We constructed calculation geometries that reproduces the actual beam delivery systems of these radiotherapy fields as precisely as possible, and confirmed consistency by comparing with measured percentage depth absorbed dose. The neutron doses and energy spectrums of ‘‘on-axis” and ‘‘off-axis” in homogeneous water phantom were calculated by irradiating each primary beams. Calculated neutron doses were compared with some published literatures. As next step, we used the Tsukuba-Plan to obtain the three-dimensional neutron dose distributions in human-shaped phantom in case of irradiating clinical beams with patient-specific devices such as bolus and collimators. We achieved a relative com-