Investigating the dosimetric impact of seed location uncertainties in Collaborative Ocular Melanoma Study-based eye plaques.

Abstract Purpose To quantify the dosimetric effects of random and systematic seed position uncertainties in Collaborative Ocular Melanoma Study–based eye plaques. Methods and Materials An eye plaque dose calculation routine was created using Task Group 43 formalism. A variety of clinical configurations were simulated, including two seed models: 125 I and 103 Pd, three eye plaque sizes, and eight plaque/eye orientations. Dose was calculated at four ocular anatomic sites and three central axis plaque depths. Random seed positional uncertainty was modeled by adding Gaussian random displacements, in one of three seed-motion degrees of freedom, to each seed's nominal coordinate. Distributions of dosimetric outcomes were obtained and fitted after 10 6 randomizations. Similar analysis was performed for deterministic, systematic shifts of the plaque along the eye surface and radially from the globe center. Results Random seed placement uncertainties of 0.2-mm root mean square (RMS) (amplitude) produce dose changes that are typically 103 Pd). Conclusions Dosimetric uncertainties due to the random seed positional displacements anticipated in the clinic are expected to be