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Monte Carlo Simulation and Validation of a Novel Yttrium-90 Source for Use in a Conformal Superficial Brachytherapy Device

B Rogers*, P Alaei , J Chmura , E Ehler , J Lawrence , C Wilke , C Ferreira , University of Minnesota, Minneapolis, MN


(Thursday, 7/18/2019) 7:30 AM - 9:30 AM

Room: 301

Purpose: To experimentally validate theoretical Monte Carlo (MC) simulations of surface profile dose and depth dose of a novel 90Y source for use in a Conformal Superficial Brachytherapy (CSBT) device for the treatment of non-melanoma skin cancers and keloids.

Methods: A newly designed brachytherapy source was created by activating ��Y disks to ��Y by neutron bombardment at the University of Missouri Research Reactor (MURR). Each ��Y disk source has a 1 mm radius and 1 mm thickness. Dose profiles and depth doses were evaluated for single and multiple sources. Measurements were made using Gafchromic EBT3 film dosimetry in a Solid Water® HE phantom. Simulations were performed with the Monte Carlo n-particle transport code (MCNP5) in photon, electron mode. The simulation space contained a 125 cm³ water phantom cube composed of 1.25x10�� cm³ cubic tally voxels. A polyenergetic electron source pertaining to the ��Y spectrum was emitted randomly within the source volume. The outputs of the simulations were the probability distributions of the energy deposited in each tally voxel for a single emitted electron (MCNP: *F8 tally). Additional measurements and MC simulations were performed at 0.1 cm depth with eight sources placed in a hexagonal distribution directly on the phantom.

Results: Using film dosimetry techniques, a single source placed directly on the film yielded a dose rate of 0.0976 Gy/s at the surface and dose rates of 0.0171 Gy/s, 0.0084 Gy/s, 0.0028 Gy/s, and 0.0006 Gy/s for 1, 2, 3, and 5 mm depths, respectively. Normalizing the MC simulations to the measured surface dose rate resulted in a 14.3% difference from the measured dose rate at 1 mm depth and a total correlation of r=0.982.

Conclusion: MC simulations were quantitatively validated and provide a basis for further investigation of ��Y for conformal brachytherapy.


Brachytherapy, Monte Carlo, Validation


TH- Brachytherapy: Development (new technology and techniques)

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