Neutron induced brachytherapy: a combination of neutron capture therapy and brachytherapy

Brachytherapy is a widely used radiation therapy modality while neutron capture therapy is being intensely studied. These methods provide some advantages, but also have limitations that might be ameliorated by combining them. A technique that uses stable solid seeds or needles of Gd which are irradiated in vivo with neutrons has been evaluated. Monte Carlo calculations show that 5000 cGy of prompt gamma dose can be delivered to a treatment volume of 40 cm3 with a three-plane implant of 9-Gd needles. The tumor to normal tissue advantage of this method is as good as brachytherapy using 60Co seeds. Measurements of prompt gamma dose with films and TLD-700s in a lucite phantom verify the Monte Carlo evaluation. Dose measurements of a Gd needle in air also show that Gd is promising for this form of brachytherapy.