SUMMARY

A boron neutron capture enhanced fast neutron therapy assembly has been designed for the Fermilab Neutron Therapy Facility (NTF). This assembly uses tungsten filter and collimator near the patient’s head with graphite reflector surrounding the head to increase significantly a dose due to boron neutron capture reactions. The assembly was designed using Monte Carlo radiation transport code, MCNP version 5 and for standard 20x20 cm2 treatment beam. The maximum boron dose enhancement of the design can be as high as 31% for 100-ppm 10B at a depth of 5 cm and a dose delivery rate of 11 cGy/min using the standard 20x20 cm2 treatment beam. To validate the design, a simplified BNCEFNT assembly was built using available materials. Measurements of the dose enhancement of the simplified assembly in a water-filled head phantom were performed using a pair of tissue equivalent ion chambers. The measurements agree very well with the calculations and thus validated the design. The increased doses to other organs due to the use of the BNCEFNT assembly were calculated using MCNP5 and a MIRD phantom. The activities of the activation products in the assembly were calculated using MCNP code.Ambient dose rate due to these activation products were computed.