Abstract
OSU‐NAG eye plaques use fewer sources than COMS‐plaques of comparable size, and do not employ a Silastic seed carrier insert. Monte Carlo modeling was used to calculate 3D dose distributions for a 16 mm OSU‐NAG eye plaque and a 16 mm COMS eye plaque loaded with either Iodine‐125 or Cesium‐131 brachytherapy sources. The OSU‐NAG eye plaque was loaded with eight sources forming two squares, whereas the COMS eye plaque was loaded with thirteen sources approximating three isocentric circles. A spherical eyeball 24.6 mm in diameter and an ellipsoid‐like tumor 6 mm in height and 12 mm in the major and minor axes were used to evaluate the doses delivered. To establish a fair comparison, a water seed carrier was used instead of the Silastic seed carrier designed for the traditional COMS eye plaque. Calculations were performed on the dose distributions along the eye plaque axis and the DVHs of the tumor, as well as the 3D distribution. Our results indicated that, to achieve a prescription dose of 85 Gy at 6 mm from the inner sclera edge for a six‐day treatment, the OSU‐NAG eye plaque will need 6.16 U/source and 6.82 U/source for 125I and 131Cs, respectively. The COMS eye plaque will require 4.02 U/source and 4.43 U/source for the same source types. The dose profiles of the two types of eye plaques on their central axes are within 9% difference for all applicable distances. The OSU‐NAG plaque delivers about 10% and 12% more dose than the COMS for 125I and 131Cs sources, respectively, at the inner sclera edge, but 6% and 3% less dose at the opposite retina. The DVHs of the tumor for two types of plaques were within 6% difference. In conclusion, the dosimetric quality of the OSU‐NAG eye plaque used in eye plaque brachytherapy is comparable to the COMS eye plaque.PACS number: 87.56B, 87.55k, 87.55kh
Highlights
Eye plaque brachytherapy is a well-recognized treatment technique for the management of ocular melanomas
Eye plaque brachytherapy has a similar survival rate compared to surgical enucleation for medium size uveal tumors.[1,2,3] The Collaborative Ocular Melanoma Study (COMS) eye plaque has been popular for decades for its standardization on plaque dimensions and number of seeds
This study evaluated the dosimetric quality of the OSU-NAG plaque in treating a sample eye tumor using both the 125I and 131Cs sources compared with the 16 mm COMS eye plaque
Summary
Eye plaque brachytherapy is a well-recognized treatment technique for the management of ocular melanomas. measurements were performed by de la Zerda et al[6] and similar results were confirmed These studies showed that the Silastic carrier and the gold plaque could reduce dose by up to 10% at a distance of 10 mm on the plaque axis compared with water. Melhus and Rivard[11] studied COMS eye plaques dose reduction due to the gold alloy and Silastic insert using Monte Carlo technique, and published the correction functions for using 6711 125I, model 200 103Pd and Cs-1 131Cs sources separately. Zhang and colleagues verified the accuracy of TG43U1 algorithm and intersource effect through a set of Monte Carlo simulations In another recently published study, Rivard et al[14] compared the dose calculation methods used in COMS eye plaque calculations. All of the above studies have added new understanding and knowledge of the COMS eye plaque
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