title: Use of a deformable atlas to identify cryptic critical structures in the treatment of glioblastoma multiforme.
abstract: Dose constraints for traditional neural critical structures (e.g. optic chiasm, brain stem) are a standard component of planning radiation therapy to the central nervous system. Increasingly, investigators are becoming interested in accounting for the dose delivered to other non-target neural structures (e.g. hippocampi), which are not easily identified on axial imaging. In this pilot study, a commercially available digital atlas was used to identify cryptic neural structures (hippocampus, optic radiations, and visual cortices) in 6 patients who received intensity modulated radiation therapy (IMRT) as part of multimodal management of glioblastoma multiforme (GBM). The patient's original IMRT plans were re-optimized, with avoidance parameters for the newly identified critical structures. Re-optimization was able to reduce both mean and maximum dose to the volumes of interest, with a more pronounced effect for contralateral structures. Mean dose was reduced by 11% and 3% to contralateral and ipsilateral structures, respectively, with comparable reduction in maximum dose of 10% and 2%, respectively. Importantly, target coverage was not compromised, with an average change in coverage of 0.2%. Overall, our results demonstrate the feasibility of incorporating tools for cryptic critical structure identification into the treatment planning process for GBM.
authors.affiliation: MD Anderson Cancer Center, Department of Radiation Oncology, University of Texas, Houston, Texas, United States of America.
authors.forename: David C
authors.initials: DC
authors.lastname: Weksberg
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Bilton
authors.forename: Eric L
authors.initials: EL
authors.lastname: Chang
mesh_terms: D001933:Brain Stem / Q000000981:diagnostic imaging; D005240:Feasibility Studies; D005909:Glioblastoma / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009897:Optic Chiasm / Q000000981:diagnostic imaging; D010865:Pilot Projects; D011832:Radiation Injuries / Q000517:prevention & control*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods* / Q000592:standards; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed