Influence of eye movement on lens dose and optic nerve target coverage during craniospinal irradiation

Bianca A W Hoeben*, Enrica Seravalli, Amber M L Wood, Mirjam Bosman, Witold P Matysiak, John H Maduro, Astrid L H M W van Lier, Matteo Maspero, Gijsbert H Bol, Geert O Janssens

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

Purpose: Optic nerves are part of the craniospinal irradiation (CSI) target volume. Modern radiotherapy techniques achieve highly conformal target doses while avoiding organs-at-risk such as the lens. The magnitude of eye movement and its influence on CSI target- and avoidance volumes are unclear. We aimed to evaluate the movement-range of lenses and optic nerves and its influence on dose distribution of several planning techniques.

Methods: Ten volunteers underwent MRI scans in various gaze directions (neutral, left, right, cranial, caudal). Lenses, orbital optic nerves, optic discs and CSI target volumes were delineated. 36-Gy cranial irradiation plans were constructed on synthetic CT images in neutral gaze, with Volumetric Modulated Arc Therapy, pencil-beam scanning proton therapy, and 3D-conventional photons. Movement-amplitudes of lenses and optic discs were analyzed, and influence of gaze direction on lens and orbital optic nerve dose distribution.

Results: Mean eye structures' shift from neutral position was greatest in caudal gaze; -5.8 +/- 1.2 mm (+/- SD) for lenses and 7.0 +/- 2.0 mm for optic discs. In 3D-conventional plans, caudal gaze decreased Mean Lens Dose (MLD). In VMAT and proton plans, eye movements mainly increased MLD and diminished D98 orbital optic nerve (D98OON) coverage; mean MLD increased up to 5.5 Gy [total Delta MLD range -8.1 to 10.0 Gy], and mean D98OON decreased up to 3.3 Gy [total Delta D98OON range -13.6 to 1.2 Gy]. VMAT plans optimized for optic disc Internal Target Volume and lens Planning organ-at-Risk Volume resulted in higher MLD over gaze directions. D98OON became >= 95% of prescribed dose over 95/100 evaluated gaze directions, while all-gaze bilateral D98OON significantly changed in 1 of 10 volunteers.

Conclusion: With modern CSI techniques, eye movements result in higher lens doses and a mean detriment for orbital optic nerve dose coverage of

Original languageEnglish
Pages (from-to)28-33
Number of pages6
JournalClinical and Translational Radiation Oncology
Volume31
DOIs
Publication statusPublished - 1-Nov-2021

Keywords

  • Craniospinal irradiation
  • VMAT
  • 3D-conventional
  • Proton
  • Lens
  • Optic nerve
  • RADIOTHERAPY
  • GERMINOMA
  • CATARACT
  • ANGLE

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