Dosimetry and fluence measurements with a new irradiation arrangement for neutron capture therapy of tumours in mice.

Incorporation of 10B in human tumours treated with fast neutrons would increase the local dose in the tumour. In tissue the neutrons are thermalized mainly causing the neutron capture reaction 10B (n,a) 7Li. The dose enhancement can be calculated using the thermal neutron fluence measured by activation of gold foils in a phantom. At a phantom depth of 5 cm a dose enhancement of (0.056 +/- 0.0028)% for each microgram of 10B per gram of tissue was determined in the tumour. A therapeutic gain by this dose enhancement in fast neutron therapy should be examined for a solid tumour in a mouse. The feasibility for neutron capture therapy of tumours in mice depends on the distribution of the tumour dose and on the effective shielding of the bodies of the mice. Therefore, a special holding device for simultaneous irradiation of four tumours was developed. The dose distribution in the tumours and in the surrounding bodies of mice was measured with TLD-300 in a special mouse phantom.