Graduate Researcher: Autumn Walter

Summary: The relative biological effectiveness (RBE) of a particular radiation quality can provide useful information about the efficacy of a particular radiation type.  However, the current body of work regarding RBE of electronic brachytherapy sources is limited. These miniature x-ray sources have a high dose rate, sharp dose fall off, and operate at energies below 70 kVp.  As a result, these sources are more sensitive to filtration materials in the radiation path length, and the LET of the low energy electrons is higher than that of the standard external beam radiation energies. The characteristics of these sources can cause problems for the current assumption that all photon sources have an RBE equal to that Co-60.

Additionally, these sources have caused challenges with dosimetric characterization, in particular with the establishment of a standard appropriate for these types of localized, low energy sources.  Currently, NIST only holds a standard for the S700 Xoft Axxent source with reference number S7500. A newer S700 Axxent model with reference number S7600 has been manufactured, but a standard has not yet been developed.  Thus, it is the primary goal of this work to dosimetrically and biologically characterize this new S7600 Axxent source, as well as assist with implementing a new standard with NIST.