Neutron capture therapy signal-to-noise ratio distribution for deep seated brain tumors

Boron and Gadolinium Neutron Capture Therapy effects are modelled using COG, a Monte Carlo radiation transport code developed and tested at Lawrence Livermore National Laboratory (LLNL) and MCNP. Calculations were performed to analyze the effect of various gadolinium concentrations on dose distribution and cell-kill effect of the GdNCT modality and to determine the optimum therapeutic conditions for treating the brain cancers. Results showed that a concentration of 100 ppm gadolinium, resulting in a signal-to-noise ratio of 1.53, was most beneficial for a deep seated tumor irradiated with an epithermal beam. A concentration of 1000 ppm, producing a ratio of 1.41, may still be advantageous, as the dose is increased without compromising the tumor to normal tissue dose ratio. The ratio decreases substantially to 1.15 for a concentration of 5000 ppm, suggesting such a high concentration may be deleterious. Calculations were also done for alternate tumor locations. (author)