Dose characteristics of Au-198 eye brachytherapy applicator: A Monte Carlo study.

PURPOSE: The use of ocular plaques is a promising treatment option for eye melanoma brachytherapy. Although several studies have been done on various ocular plaques, little is known about the dose characterization of 198Au plaque.

MATERIALS AND METHOD: The full mathematical model of the eye phantom, tumor, 106Ru/106Rh CCA, and 198Au plaque were simulated using the Monte Carlo MCNPX code. The dose distribution was measured in the plaque's central axis direction, and a dose profile was also measured at a distance of 2.5 mm from the plaque surface.

RESULTS

The findings showed that 198Au plaque has superior dosimetric characteristics than CCA plaque for tumors with a thickness of greater than 3.5 mm, while CCA plaque is better for tumors with a thickness of less than 3.5 mm. The dose to the sclera and choroid is higher in the case of CCA plaque, while the dose to the organs at risk (lens and optic nerve) is greater in the case of 198Au applicator. In the case of 198Au plaque, however, the dose to sensitive organs was within their permissible dose range.

CONCLUSION

In the treatment of medium and large tumors, 198Au plaque is more successful than CCA plaque. It can produce a much more homogeneous lateral dose profile in the target. In the treatment of dome-shaped tumors, 198Au plaque may be more successful than CCA plaque. As a result, the tumor's shape influences the plaque type selection.