AbstractID: 9162 Title: Dose Rate Characterization of a High Dose-Rate 103Pd Applicator using MCNP4C
The characterization of the dose profile from a high dose-rate 103Pd applicator was calculated using MCNP4C. The applicator is being developed
by Theragenics Corporation® for potential use in the treatment of Age-Related Macular Degeneration (ARMD). The source design includes a
cylindrical stainless steel holder which contains the 103Pd. The active portion of the device has an outer diameter of 5.0-mm. The holder is
designed to minimize the photon transport to locations peripheral and posterior to the device. The source was modeled in its as-built condition
and surrounded by a 30-cm water sphere. The dose to water was calculated using both surface and volume detectors at axial distances ranging
from z= 0 to 0.25-mm and radial distances from r=0 to 20-mm. The results from the surface detector tallies are used to calculate a 2-dimensional
representation of the isodose contours. The volume detector results are used to calculate a dose volume histogram (DVH) for the dose to the eye
and to an idealized target volume with a cylindrical shape 3-mm in diameter, with an axial thickness from z = 1.5-mm to 3.0-mm. The results
from this modeling indicate that the diameter of the 90% isodose contour located at the prescription depth of 3.0-mm is greater than 3.0-mm. No
portion of the idealized target volume receives greater than 200% of the prescription dose, while 90% of the remainder of the eye receives less
than 20% of the prescription dose. The authors are employees or consultants of Theragenics Corporation®.