Room: ePoster Forums
Purpose: The purpose of this study was to compare Collaborative Ocular Melanoma Study (COMS) eye plaque dosimetry using I-125 seeds in â€œseedâ€? source geometry from CMS Xio TPS commissioned prior to AAPM TG-129 report with plaque dosimetry arising from Eclipse BrachyVision and MIM Symphony TPS using the linear source model.
Methods: Six patients with plaque sizes ranging from 12 mm to 22m in 2mm increments who were previously treated for choroidal melanoma using I-125 COMS eye plaques were chosen for this study. All patients received 85 Gy to 5mm depth using homogeneous dosimetry computed with CMS Xio TPS using â€œseedâ€? source approximation. The patientâ€™s plaque dosimetry was recalculated in Eclipse BrachyVision and MIM Symphony TPS. I-125 source incorporating a linear source model using 2D cylindrically symmetric line source equations as described in updated TG-43U1 protocol was used to calculate the plaque dosimetry in Eclipse BrachyVision and MIM Symphony TPS.
Results: The 2D line source geometry calculation from Eclipse BrachyVision and MIM Symphony TPS for all plaque sizes was clinically comparable (â‰¤ 3% difference) to the dosimetry from CMS Xio using seed source geometry for all the relevant interest points compared namely Tumor Apex, Macula, Opposite Retina, Optic Disc,and Lens Center.
Conclusion: There were no clinically relevant differences to anatomical points of interest arising from plaque dosimetry between the three TPS using a prescription dose of 85 Gy to 5mm depth. This is likely due to the fact that COMS plaque source positioning aligns the transverse planes of every source with the plaque central-axis thus producing equivalent doses between 1D and 2D dose calculation formalism.