PURPOSE: Novel plaques are used to treat iris melanoma at the Mayo Clinic Rochester. The plaques are a modification of the Collaborative Ocular Melanoma Study (COMS) 22 mm plaque design with a gold alloy backing, outer lip, and silicone polymer insert. An inner lip surrounds a 10 mm diameter cutout region at the plaque center. Plaques span 360°, 270°, and 180° arcs. This article describes dosimetry for these plaques and others used in the treatment of anterior eye melanomas. METHODS AND MATERIALS: The EGSnrc user-code BrachyDose is used to perform Monte Carlo simulations. Plaques and seeds are fully modeled. Three-dimensional dose distributions for different plaque models, TG-43 calculations, and (125)I (model 6711) and (103)Pd (model 200) seeds are compared via depth-dose curves, tabulation of doses at points of interest, and isodose contours. RESULTS: Doses at points of interest differ by up to 70% from TG-43 calculations. The inner lip reduces corneal doses. Matching plaque arc length to tumor extent reduces doses to eye regions outside the treatment area. Maintaining the same prescription dose, (103)Pd offers lower doses to critical structures than (125)I, with the exception of the sclera adjacent to the plaque. CONCLUSION: The Mayo Clinic plaques offer several advantages for anterior eye tumor treatments. Doses to regions outside the treatment area are significantly reduced. Doses differ considerably from TG-43 predictions, illustrating the importance of complete Monte Carlo simulations. Calculations take a few minutes on a single CPU, making BrachyDose sufficiently fast for routine clinical treatment planning.
PURPOSE: Novel plaques are used to treat iris melanoma at the Mayo Clinic Rochester. The plaques are a modification of the Collaborative Ocular Melanoma Study (COMS) 22 mm plaque design with a gold alloy backing, outer lip, and silicone polymer insert. An inner lip surrounds a 10 mm diameter cutout region at the plaque center. Plaques span 360°, 270°, and 180° arcs. This article describes dosimetry for these plaques and others used in the treatment of anterior eye melanomas. METHODS AND MATERIALS: The EGSnrc user-code BrachyDose is used to perform Monte Carlo simulations. Plaques and seeds are fully modeled. Three-dimensional dose distributions for different plaque models, TG-43 calculations, and (125)I (model 6711) and (103)Pd (model 200) seeds are compared via depth-dose curves, tabulation of doses at points of interest, and isodose contours. RESULTS: Doses at points of interest differ by up to 70% from TG-43 calculations. The inner lip reduces corneal doses. Matching plaque arc length to tumor extent reduces doses to eye regions outside the treatment area. Maintaining the same prescription dose, (103)Pd offers lower doses to critical structures than (125)I, with the exception of the sclera adjacent to the plaque. CONCLUSION: The Mayo Clinic plaques offer several advantages for anterior eye tumor treatments. Doses to regions outside the treatment area are significantly reduced. Doses differ considerably from TG-43 predictions, illustrating the importance of complete Monte Carlo simulations. Calculations take a few minutes on a single CPU, making BrachyDose sufficiently fast for routine clinical treatment planning.
Authors: Kirtesh R Patel; Roshan S Prabhu; Jeffrey M Switchenko; Mudit Chowdhary; Caroline Craven; Pia Mendoza; Hasan Danish; Hans E Grossniklaus; Thomas M Aaberg; Thomas Aaberg; Sahitya Reddy; Elizabeth Butker; Chris Bergstrom; Ian R Crocker Journal: Brachytherapy Date: 2017-03-03 Impact factor: 2.362
Authors: Mark J Rivard; Sou-Tung Chiu-Tsao; Paul T Finger; Ali S Meigooni; Christopher S Melhus; Firas Mourtada; Mary E Napolitano; D W O Rogers; Rowan M Thomson; Ravinder Nath Journal: Med Phys Date: 2011-01 Impact factor: 4.071
Authors: Wu Liu; Jenna May Kim; Benjamin K Young; Ravinder Nath; Zhe Chen; Roy H Decker; Melvin A Astrahan; Renelle Pointdujour-Lim Journal: Ocul Oncol Pathol Date: 2018-10-11