MRI-based treatment planning and dose delivery verification for intraocular melanoma brachytherapy

Jacqueline Esthappan Zoberi, Jose Garcia-Ramirez, Samantha Hedrick, Vivian Rodriguez, Carol G. Bertelsman, Stacie Mackey, Yanle Hu, H. Michael Gach, P. Kumar Rao, Perry W. Grigsby

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

Purpose Episcleral plaque brachytherapy (EPB) planning is conventionally based on approximations of the implant geometry with no volumetric imaging following plaque implantation. We have developed an MRI-based technique for EPB treatment planning and dose delivery verification based on the actual patient-specific geometry. Methods and Materials MR images of 6 patients, prescribed 85 Gy over 96 hours from Collaborative Ocular Melanoma Study–based EPB, were acquired before and after implantation. Preimplant and postimplant scans were used to generate “preplans” and “postplans” respectively. In the preplans, a digital plaque model was positioned relative to the tumor, sclera, and nerve. In the postplans, the same plaque model was positioned based on the imaged plaque. Plaque position, point doses, percentage of tumor volume receiving 85 Gy (V100), and dose to 100% of tumor volume (Dmin) were compared between preplans and postplans. All isodose plans were computed using TG-43 formalism with no heterogeneity corrections. Results Shifts and tilts of the plaque ranged from 1.4 to 8.6 mm and 1.0 to 3.8 mm, respectively. V100 was ≥97% for 4 patients. Dmin for preplans and postplans ranged from 83 to 118 Gy and 45 to 110 Gy, respectively. Point doses for tumor apex and base were all found to decrease from the preimplant to the postimplant plan, with mean differences of 16.7 ± 8.6% and 30.5 ± 11.3%, respectively. Conclusions By implementing MRI for EPB, we eliminate reliance on approximations of the eye and tumor shape and the assumption of idealized plaque placement. With MRI, one can perform preimplant as well as postimplant imaging, facilitating EPB treatment planning based on the actual patient-specific geometry and dose-delivery verification based on the imaged plaque position.

Original languageEnglish (US)
Pages (from-to)31-39
Number of pages9
JournalBrachytherapy
Volume17
Issue number1
DOIs
StatePublished - Jan 2018

Keywords

  • Brachytherapy
  • Dosimetry
  • Magnetic resonance imaging
  • Melanoma
  • Ocular

ASJC Scopus subject areas

  • Oncology
  • Radiology Nuclear Medicine and imaging

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    Zoberi, J. E., Garcia-Ramirez, J., Hedrick, S., Rodriguez, V., Bertelsman, C. G., Mackey, S., Hu, Y., Gach, H. M., Rao, P. K., & Grigsby, P. W. (2018). MRI-based treatment planning and dose delivery verification for intraocular melanoma brachytherapy. Brachytherapy, 17(1), 31-39. https://doi.org/10.1016/j.brachy.2017.07.011