Collimator DESIGN OPTIMIZATION AND CANCER THERAPY dosimetry soft tissue sarcomas THE NECK AND HEAD WITH BORON NEUTRON CAPTURE THERAPY FOR Cyclotron 30 MEV NEUTRON SOURCE PROGRAM USING MONTE CARLO N PARTICLE X
ABSTRACT: Boron neutron capture therapy (BNCT) has been proposed as a cancer treatment when other therapy methods are not possible. One major concern is whether a Neutron Beam Shaping Assembly (NBSA) could be designed such that it is suitable for each patient depending on tumor depth, size and kind of cancer. So, it is needed to study the optimization of collimator design for BNCT based cyclotron 30 MeV and its dosimetry simulation in head and neck soft tissue sarcoma using Monte Carlo N Particle X program. This study involves two main objectives for BNCT system. First goal includes optimization of cyclotron based BNCT collimator. Second goal is to calculate the neutron flux and dosimetry system of Boron Neutron Capture Therapy (BNCT) in head and neck soft tissue sarcoma (STS). A series of simulations has been carried out using a Monte Carlo N Particle-X program to find out the final composition and configuration of a collimator to moderate the fast neutron flux which is generated from the thick beryllium target. The final configuration for collimator design included 39 cm aluminium as moderator, 8,2 cm lithium fluoride as fast neutron filter and 0,5 cm boron carbide as thermal neutron filter. Bismuth, lead, and lead fluoride were chosen as the aperture, reflector, and gamma shielding, respectively. Epithermal neutron flux in the suggested design were 2,83E9 n/cm^2s, while other IAEA parameters for BNCT collimator design had been satisfied. In the next step, dosimetry evaluation for head and neck soft tissue sarcoma was simulated by MCNPX program. Simulations were carried out by varying the concentration of boron compounds in ORNL neck phantom model to obtained the optimal dosimetry results. MCNPX calculation showed that the optimal depth for thermal neutron was 4,8 cm in tissue phantom with the maximum dose rate was in GTV on each boron concentration variation. The irradiated time needed for this therapy for each variables were less than an hour.
