title: Deformation field validation and inversion applied to adaptive radiation therapy.
abstract: Development and implementation of chronological and anti-chronological adaptive dose accumulation strategies in adaptive intensity-modulated radiation therapy (IMRT) for head-and-neck cancer. An algorithm based on Newton iterations was implemented to efficiently compute inverse deformation fields (DFs). Four verification steps were performed to ensure a valid dose propagation: intra-cell folding detection finds zero or negative Jacobian determinants in the input DF; inter-cell folding detection is implemented on the resolution of the output DF; a region growing algorithm detects undefined values in the output DF; DF domains can be composed and displayed on the CT data. In 2011, one patient with nonmetastatic head and neck cancer selected from a three phase adaptive DPBN study was used to illustrate the algorithms implemented for adaptive chronological and anti-chronological dose accumulation. The patient received three (18)F-FDG-PET/CTs prior to each treatment phase and one CT after finalizing treatment. Contour propagation and DF generation between two consecutive CTs was performed in Atlas-based autosegmentation (ABAS). Deformable image registration based dose accumulations were performed on CT1 and CT4. Dose propagation was done using combinations of DFs or their inversions. We have implemented a chronological and anti-chronological dose accumulation algorithm based on DF inversion. Algorithms were designed and implemented to detect cell folding.
authors.affiliation: Department of Radiotherapy, Ghent University Hospital, Belgium. tom.vercauteren@uzgent.be
authors.forename: Tom
authors.initials: T
authors.lastname: Vercauteren
authors.forename: Werner
authors.initials: W
authors.lastname: De Gersem
authors.forename: Luiza A M
authors.initials: LA
authors.lastname: Olteanu
authors.forename: Indira
authors.initials: I
authors.lastname: Madani
authors.forename: Fréderic
authors.initials: F
authors.lastname: Duprez
authors.forename: Dieter
authors.initials: D
authors.lastname: Berwouts
authors.forename: Bruno
authors.initials: B
authors.lastname: Speleers
authors.forename: Wilfried
authors.initials: W
authors.lastname: De Neve
mesh_terms: D000465:Algorithms; D019788:Fluorodeoxyglucose F18; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D006801:Humans; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed
chemical_list: D019788:Fluorodeoxyglucose F18