Date of Graduation


Document Type

Thesis (MS)

Program Affiliation

Medical Physics

Degree Name

Masters of Science (MS)

Advisor/Committee Chair

Geoffrey Ibbott, Ph.D.

Committee Member

David Followill, Ph.D.

Committee Member

Kent Gifford, Ph.D.

Committee Member

Ramesh Tailor, Ph.D.

Committee Member

Shouhao Zhou, Ph.D.


With continuing advances in the burgeoning field of electronic brachytherapy, an accurate method of 3D dosimetry is needed to ensure understanding of dose distributions, which can improve patient care. The aim of this study was to characterize the Xoft Axxent electronic brachytherapy source using PRESAGETM dosimeters in order to obtain independent confirmation of TG-43U1 dosimetry values, as well as to further add to the literature of both Xoft and PRESAGE.

PRESAGE is a polyurethane-based solid 3D dosimeter doped with a radiochromic leuco dye which produces a linear change in optical density when exposed to radiation. This optical density change is imaged using an optical-CT scanner and reconstructed for analysis using MATLAB software. A Xoft source with a measured air kerma strength of 126095 U was used in this experiment to irradiate 8 PRESAGE dosimeters to 15 Gy at 1 cm in order to evaluate the dose rates from r=1 cm to r=5 cm. The dosimetric parameters were calculated and compared to the Rivard et al. (1) parameters.

In general, the measured results closer to the source more closely matched the comparison data than those values measured further from the source. The radial dose function was within 6% of the expected values, and the anisotropy function, ignoring the extreme outlier at each radius, was within 35% of the expected values. An incorrect shutter value was used when imaging the dosimeters so that the post-irradiation scans were repeated 2 months after the irradiation, allowing time for the dosimeter to darken as it aged, which increased background noise, and time for the dose signal to fade, thereby bringing the dose signal closer to the background noise. The experiment should be repeated to obtain more accurate results.