Dosimetry of 252Cf sources for neutron radiotherapy with and without augmentation by boron neutron capture therapy

Interstitial and intracavity 252Cf sources have been used to treat a number of tumor types with encouraging results. In particular these tumors include a variety of cervical, head-and-neck, and oral-cavity cancers and possible malignant gliomas. As a neutron source, 252Cf offers certain theoretical advantages over photon therapy (i.e., in treating tumors with significant hypoxic or necrotic components). With the recent availability of 10B-labeled tumor-seeking compounds, the usefulness of 252Cf may be further improved by augmenting the 252Cf dose to the tumor with an additional dose due to the fission (following thermal neutron capture) of 10B located in the tumor itself. While the high mean neutron energy permits 252Cf to deliver a high-LET, low-OER dose to the tumor on a macroscopic scale, thermalization of neutrons followed by 10B capture may augment this dose at the cellular level if adequate loading of tumor cells with 10B is possible. This paper presents results of a Monte Carlo simulation study investigating the dosimetric characteristics of linear 252Cf sources both with and without the quantitative increase in tumor dose possible with the addition of 10B. Results are displayed in the form of "along and away" tables and dose profiles in a water phantom. Comparisons of Monte Carlo results with experimental and analytical dosimetry data available in the literature are also presented.