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Purpose: To provide a dosimetric characterization of the Xoft Axxent™ source within a titanium cervical applicator using liquid water dosimetry and Monte Carlo simulation methods. Methods: Absorbed dose to water measurements were performed using an annulus of Virtual Water™ (referred to as the Captains Wheel) that is mounted in a water phantom to allow measurements in liquid water. The Captains Wheel permits the precise placement of TLD‐100 microcubes around the applicator using aluminum radial gauges of radii 1, 2, 3, and 4 cm. This geometry allows determination of the dose‐rate constant, radial dose function, and azimuthal anisotropy. The air‐kerma strength was measured using the Attix Free‐Air Chamber at the UWADCL and well chamber measurements were completed using two Standard Imaging HDR1000 Plus well chambers. Measurements were performed using two Axxent™ sources calibrated at NIST. Monte Carlo simulations were also performed using MCNP5 based on specifications provided by the manufacturer to calculate the dose‐rate constant, radial dose function, and polar anisotropy. MCNP5 was used to generate the source spectrum exiting the titanium applicator for comparison to the experimental results. Results: The Monte Carlo dose‐rate constant was 3.6% higher than the experimentally determined dose‐rate constant. The radial dose value at 2 cm calculated for a 6 mm pullback distance was 3.5% lower when compared to the measured radial dose value at 2 cm. The azimuthal anisotropy measurements were normalized to the smallest TLD reading at a given distance, with a maximum anisotropy value of 1.27 at 2 cm. Conclusion: TG‐43 parameters were experimentally determined and compared to Monte Carlo simulations for the Axxent™ source within a titanium applicator. Conflict of Interest: Xoft Inc. provided financial support, sources, and applicators. Xoft Inc. provided financial support, sources, and applicators. |
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