Applications of Californium-252 and the Californium User Facility for Neutron Capture Therapy Research

Abstract

Neutrons for neutron capture therapy (NCT) are potentially available from three sources: nuclear reactors, accelerators, and 252Cf radioisotope sources. A small number of reactors are currently or will soon become available for NCT. The costs of building and operating a reactor are too large to justify NCT-only usage. Accelerators which can provide effective NCT treatments are nearing realization, but the potential cost, except for boron neutron capture synovectomy, is sobering. The epithermal flux from available 252Cf neutron sources is too low for conventional NCT, but 252Cf can potentially provide a valuable contribution in several ways: (1) provide a neutron flux for testing NCT pharmaceuticals such as boron-containing compounds in vitro; (2) provide a neutron flux for skin and near-surface neutron therapy; (3) provide a neutron driver for a subcritical multiplying assembly (SMA) for epithermal beam generation; and (4) provide miniature sources for neutron brachytherapy (i.e., inserting the source inside the body into the tumor location), which can be used in conjunction with NCT pharmaceuticals. Although an appropriately designed SMA could provide a hospital-based neutron source for NCT at a limited number of sites, neutron brachytherapy represents the greatest medical potential of 252Cf in bringing relatively low-cost neutron therapy to a large number of clinical locations.