Transport calculations of depth-dose distributions for gadolinium neutron capture therapy.

Depth-dose distributions were calculated for thermal and epithermal neutron fluence and capture gamma ray dose rates using a two-dimensional neutron-coupled gamma-ray transport code (DOT 3.5) for gadolinium neutron capture therapy. The results show that (i) a capture gamma-ray dose rate of 10 Gy h-1 was obtained with a thermal neutron fluence rate of 1.5 x 10(9) cm-2 s-1 in a simulated tumour containing 5000 PPM gadolinium placed near the surface of a water phantom, (ii) deep-seated tumours may be treated with epithermal neutrons, and (iii) gadolinium neutron capture therapy appears to achieve comparable dose distributions to those of boron neutron capture therapy.