  The effects of gold nanoparticles in 125I brachytherapy dose enhancement on
choroidal Melanoma are examined using the Monte Carlo simulation technique.
Usually, Monte Carlo ophthalmic brachytherapy dosimetry is performed in a water
phantom. However, here, the compositions of human eye have been considered
instead of water. Both human eye and water phantoms have been simulated with
MCNP5 code. These simulations were performed for a fully-loaded 16 mm COMS eye
plaque containing 13 125I seeds. The dose delivered to the tumor and healthy
tissues have been calculated in both phantoms, with and without GNPs. The
results indicates that the dose to the tumor in an eye-ball implanted with COMS
plaque increases with increasing GNPs concentration inside the target.
Therefore, the required irradiation time for the tumors in the eye is decreased
by adding the GNPs prior to treatment. As a result, the dose to healthy tissues
decreases when the irradiation time is reduced. Furthermore, a comparison
between the simulated data in an eye phantom made of water and eye phantom made
of human-eye composition, in the presence of GNPs shows the significance of
utilizing the composition of eye in ophthalmic brachytherapy dosimetry.
Normally, the radiation therapy of cancer patients is designed to deliver a
required dose to the tumor while sparing the surrounding healthy tissues. The
results demonstrated that the use of GNPs enable us to overcome this challenge.
Also, defining the eye composition instead of water will leads to more accurate
calculations of GNPs radiation effects in ophthalmic brachytherapy dosimetry.
