Monte Carlo Simulation of the Treatment of Uveal Melanoma Using Measured Heterogeneous ¹⁰⁶Ru Plaques

Ruthenium plaques are used for the treatment of ocular tumors. The aim of this work is the comparison between simulated absorbed dose distributions tallied in an anthropomorphic phantom, obtained from ideal homogeneous plaques, and real eye plaques in which the actual heterogeneous distribution of ¹⁰⁶Ru was measured. The placement of the plaques with respect to the tumor location was taken into consideration to optimize the effectiveness of the treatment.

The generic CCA and CCB, and the specific CCA1364 and CCB1256 ¹⁰⁶Ru eye plaques were modeled with the Monte Carlo code PENELOPE. To compare the suitability of each treatment for an anterior, equatorial and posterior tumor location, cumulative dose-volume histograms for the tumors and structures at risk were calculated.

Eccentric placements of the plaques, taking into account the inhomogeneities of the emitter map, can substantially reduce the dose delivered to structures at risk while maintaining the prescribed dose at the tumor apex.

The emitter map distribution of the plaque and the computerized tomography of the patient used in a Monte Carlo simulation allow an accurate determination of the plaque position with respect to the tumor with the potential to reduce the dose to sensitive structures.