ESTRO 2024 - Abstract Book

S4035

Physics - Inter-fraction motion management and offline adaptive radiotherapy

ESTRO 2024

Dose mapping between image sets is subject to errors, including contouring and registration or deformation errors. By considering image intensity deformation and OAR contour deformations separately, an estimate of these errors has been incorporated into the dose mapping process. The resultant RMOD were only marginally higher than those resulting from imaging registration by the global hybrid image-structure deformation. Whilst preserving dosimetric headroom, RMOD reduced underestimates and improved robustness for planning of further RT. For very small structures, RMOD becomes equivalent to using a point maximum dose taken from the original unmapped dose, which is the most conservative and appropriate option in such cases.

Keywords: deformable registration, dose mapping, robustness

References:

1. Brock KK, Mutic S, McNutt TR, Li H, Kessler ML. Use of image registration and fusion algorithms and techniques in radiotherapy: Report of the AAPM Radiation Therapy Committee Task Group No. 132. Med Phys. 2017, 44(7): e43-e76

2. Amstutz, F; Nenoff, L; Albertini, F; O Ribeiro, C; Knopf, A; Unkelbach, J; Weber, D; Lomax, A ; Zhang, Y. An approach for estimating dosimetric uncertainties in deformable dose accumulation in pencil beam scanning proton therapy for lung cancer. Phys. Med. Biol. 2021, 66, 105007.

1408

Digital Poster

Toward individual adaptive voxel-based prediction of visual outcomes in paraoptic H&N or CNS tumors

Nathan Azemar 1 , Cathy Fontbonne 1 , Jean-Marc Fontbonne 1 , Juliette Thariat 1,2

1 CNRS/IN2P3, LPC Caen UMR6534, Caen, France. 2 Centre François Baclesse, Radiation oncology, Caen, France

Purpose/Objective:

Modelling of radiation effects have mainly been based on retrospective cohorts using tabular data of visual outcomes, often by patient self-report of significant vision losses, and discrete dose metrics based on radiotherapy planning data. Voxel-based analysis of 3D dose maps and dose distribution to sub-functional units of the optic structures (retina/macula, papillas/optic nerves, chiasma, corneas, lenses, posterior optic radiation tracts) are currently lacking to accurately characterize individual dose-volume effects. Individual visual outcomes can be detected early using standardized sensitive ophthalmological morphologic and functional exams [1-3]. The amplitude of eye movements during the radiotherapy course, compared to the planning radiotherapy CT, is largely unknown, despite massive implementation of image-guided radiotherapy and recognition of the needs for adaptive radiotherapy. Patients with head and neck or CNS tumors, including those with tumors approaching the optic pathways, undergo radiotherapy with eye movements left uncontrolled (eyes closed, no specific gazing recommendations). We report a voxel-based analysis of the impact of gaze direction on dose distribution as part of a vision modeling study.