title: Development of Monte Carlo based real-time treatment planning system with fast calculation algorithm for boron neutron capture therapy.
abstract: OBJECTIVE
  We simulated the effect of patient displacement on organ doses in boron neutron capture therapy (BNCT). In addition, we developed a faster calculation algorithm (NCT high-speed) to simulate irradiation more efficiently.
  
  
  METHODS
  We simulated dose evaluation for the standard irradiation position (reference position) using a head phantom. Cases were assumed where the patient body is shifted in lateral directions compared to the reference position, as well as in the direction away from the irradiation aperture. For three groups of neutron (thermal, epithermal, and fast), flux distribution using NCT high-speed with a voxelized homogeneous phantom was calculated. The three groups of neutron fluxes were calculated for the same conditions with Monte Carlo code. These calculated results were compared.
  
  
  RESULTS
  In the evaluations of body movements, there were no significant differences even with shifting up to 9mm in the lateral directions. However, the dose decreased by about 10% with shifts of 9mm in a direction away from the irradiation aperture. When comparing both calculations in the phantom surface up to 3cm, the maximum differences between the fluxes calculated by NCT high-speed with those calculated by Monte Carlo code for thermal neutrons and epithermal neutrons were 10% and 18%, respectively. The time required for NCT high-speed code was about 1/10th compared to Monte Carlo calculation.
  
  
  CONCLUSIONS
  In the evaluation, the longitudinal displacement has a considerable effect on the organ doses. We also achieved faster calculation of depth distribution of thermal neutron flux using NCT high-speed calculation code.
authors.affiliation: Faculty of Medicine, University of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki 305-8575, Japan. Electronic address: k-takada@md.tsukuba.ac.jp.
authors.forename: Kenta
authors.initials: K
authors.lastname: Takada
authors.affiliation: Faculty of Medicine, University of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki 305-8575, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kumada
authors.affiliation: NAIS Co., Inc., 416, Muramatsu, Tokai-mura, Naka-gun, Ibaraki 319-1112, Japan.
authors.forename: Peng Hong
authors.initials: PH
authors.lastname: Liem
authors.affiliation: Faculty of Medicine, University of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki 305-8575, Japan.
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Sakurai
authors.affiliation: Faculty of Medicine, University of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki 305-8575, Japan.
authors.forename: Takeji
authors.initials: T
authors.lastname: Sakae
mesh_terms: D000465:Algorithms; D016754:Boron Neutron Capture Therapy; D004058:Diffusion; D006801:Humans; D009010:Monte Carlo Method; D009068:Movement; D009502:Neutrons; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D013696:Temperature; D013997:Time Factors; D035501:Uncertainty
keywords: BNCT; Fast calculation; PHITS; Real-time dose evaluation