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Delivered dose changes in COMS plaque-based ocular brachytherapy arising from vitrectomy with silicone oil replacement.
Morrison, Hali; Larocque, Matthew P; Menon, Geetha; Sloboda, Ron S; Weis, Ezekiel.
Afiliación
  • Morrison H; Department of Oncology, University of Alberta, Edmonton, Alberta, Canada; Department of Medical Physics, Tom Baker Cancer Centre, Calgary, Alberta, Canada. Electronic address: hamorris@ualberta.ca.
  • Larocque MP; Department of Oncology, University of Alberta, Edmonton, Alberta, Canada; Department of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada.
  • Menon G; Department of Oncology, University of Alberta, Edmonton, Alberta, Canada; Department of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada.
  • Sloboda RS; Department of Oncology, University of Alberta, Edmonton, Alberta, Canada; Department of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada.
  • Weis E; Department of Ophthalmology, University of Alberta, Edmonton, Alberta, Canada; Department of Surgery, University of Calgary, Calgary, Alberta, Canada.
Brachytherapy ; 18(5): 668-674, 2019.
Article en En | MEDLINE | ID: mdl-31272841
PURPOSE: The purpose of the study was to determine dosimetric effects of performing concurrent I-125 Collaborative Ocular Melanoma Study plaque brachytherapy and vitrectomy with replacement using silicone oil, previously shown to be a means of shielding uninvolved parts of the eye. METHODS AND MATERIALS: Monte Carlo simulations using MCNP6 were performed to compare the dosimetry with all eye materials assigned as water, and for the vitreous (excluding the tumor), composed of polydimethylsiloxane oil for three generic, one large tumor, and two patient geometry scenarios. Dose was scored at the tumor apex, along the sclera, and within a 3D grid encompassing the eye. The assessed patient cases included vitrectomies to treat intraocular pathologies; not to enhance attenuation/shielding. RESULTS: The doses along the sclera and for the entire eye were decreased when the silicone oil replaced the vitreal fluid, with a maximum decrease at the opposite sclera of 63%. Yet, absolute changes in dose to critical structures were often small and likely not clinically significant. The dose at the tumor apex was decreased by 3.1-9.4%. Dose was also decreased at the edges of the tumor because of decreased backscatter at the tumor-oil interface. CONCLUSIONS: Concurrent silicone vitrectomy was found to reduce total radiation dose to the eye. Based on current radiation retinopathy predictive models, the evaluation of the absolute doses revealed only a subset of patients in which a clinically significant difference in outcomes is expected. Furthermore, the presence of the silicone oil decreased dose to the tumor edges, indicating that the tumor could be underdosed if the oil is unaccounted for.
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Texto completo: 1 Colección: 01-internacional Base de datos: MEDLINE Asunto principal: Traumatismos por Radiación / Vitrectomía / Braquiterapia / Neoplasias del Ojo / Melanoma Tipo de estudio: Etiology_studies / Health_economic_evaluation / Prognostic_studies Límite: Humans Idioma: En Revista: Brachytherapy Asunto de la revista: RADIOTERAPIA Año: 2019 Tipo del documento: Article Pais de publicación: Estados Unidos
Texto completo
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Texto completo: 1 Colección: 01-internacional Base de datos: MEDLINE Asunto principal: Traumatismos por Radiación / Vitrectomía / Braquiterapia / Neoplasias del Ojo / Melanoma Tipo de estudio: Etiology_studies / Health_economic_evaluation / Prognostic_studies Límite: Humans Idioma: En Revista: Brachytherapy Asunto de la revista: RADIOTERAPIA Año: 2019 Tipo del documento: Article Pais de publicación: Estados Unidos