Dosimetry in boron neutron capture therapy

Boron neutron capture therapy is based on the irradiation of charged particles in the tumour cells. The dose in the tumour is equal to the total energy from the 10B(n,α)7 Li reaction, which is proportional to the product of the neutron fluence and the 10B concentration in the tumour. Dosimetry for medical therapy implies the monitoring of the neutron fluence and the measurement of 10B concentrations. The neutron fluence was determined by miniaturized silicon detectors covered with 6LiF. The detectors are manufactured in our laboratory and have been successfully utilized for clinical purposes. The 10B concentrations have, up to now, been measured by chemical analysis. Another measuring system is being studied for practical application. In this system the 0.48 MeV prompt gamma rays emitted from 7Li nuclei are detected by Ge(Li) gamma detectors. Errors are 3% for 30 ppm of 10B and 30% for 1 ppm of 10B when the sample volume is 0.28 cm3 and the counting time is 1000 seconds. Some clinical results of the boron neutron capture therapy are also described. (author)