Californium-252 as a Neutron Source for BNCT

Abstract

Californium-252 sources are used in several cancer institutions for clinical interstitial or intracavitary neutron brachytherapy. The dose deposited from the fast neutron and gamma irradiation components from a Cf-252 source is the main therapeutic agent for these treatment techniques. The symmetrical, isotropic nature of the dose distribution and the relatively small number of available source positions for the case of high dose rate intracavitary brachytherapy make it difficult to obtain good conformality of irregularly shaped targets. Furthermore, the rapid dose fall-off from a brachytherapy source often compromises the dose to the areas of potential tumour micro-invasion. Administration of Gd-157 pellets (seeds or needles) to the planned position alter the primary absorbed dose distribution of the high dose rate Cf-252 source to best conform the irregularly shaped tumour and sufficiently irradiate areas of micro-invasion. The thermal neutron fluence from a Cf-252 source is often used as an external source for neutron induced brachytherapy.