Contouring in the optic plane improves the accuracy of computed tomography-based segmentation of the optic pathway

Eric Walther, Lynn Griffin, Elissa Randall, Lynne Sandmeyer, Stephanie Osinchuk, Sally Sukut, Katherine Hansen, Michele Keyerleber, Jessica Lawrence, Sarah Parker, Monique Mayer

Research output: Contribution to journalArticlepeer-review


Canine optic pathway structures are often contoured on CT images, despite the difficulty of visualizing the optic pathway with CT using standard planes. The purpose of this prospective, analytical, diagnostic accuracy study was to examine the accuracy of optic pathway contouring by veterinary radiation oncologists (ROs) before and after training on optic plane contouring. Optic pathway contours used as the gold standard for comparison were created based on expert consensus from registered CT and MRI for eight dogs. Twenty-one ROs contoured the optic pathway on CT using their preferred method, and again following atlas and video training demonstrating contouring on the optic plane. The Dice similarity coefficient (DSC) was used to assess contour accuracy. A multilevel mixed model with random effects to account for repeated measures was used to examine DSC differences. The median DSC (5th and 95th percentile) before and after training was 0.31 (0.06, 0.48) and 0.41 (0.18, 0.53), respectively. The mean DSC was significantly higher after training compared with before training (mean difference = 0.10; 95% CI, 0.08–0.12; P < 0.001) across all observers and patients. DSC values were comparable to those reported (0.4–0.5) for segmentation of the optic chiasm and nerves in human patients. Contour accuracy improved after training but remained low, potentially due to the small optic pathway volumes. When registered CT-MRI images are not available, our study supports routine addition of an optic plane with specific window settings to improve segmentation accuracy in mesaticephalic dogs ≥11 kg.

Original languageEnglish (US)
Pages (from-to)768-774
Number of pages7
JournalVeterinary Radiology and Ultrasound
Issue number4
StatePublished - Jul 2023

Bibliographical note

Funding Information:
The authors acknowledge Gregory Almond, Julia Buchholz, James Custis, John Farrelly, Dah‐Renn Fu, Michael Kent, Miriam Kleiter, Carolynne Kruckman‐Gatesy, Lyndsay Kubicek, Thomas Lee, Leanne Magestro, Charles Maitz, Tiffany Martin, Valeria Meier, Koichi Nagata, Isabella Pfeiffer, Valerie Poirier, and Kimberly Selting for their valuable contribution to this study through participation in both contouring phases. The resident's (E.W.) salary and research costs were funded by PetCure Oncology.

Publisher Copyright:
© 2023 American College of Veterinary Radiology.


  • cross-sectional imaging
  • radiation oncology
  • veterinary

PubMed: MeSH publication types

  • Journal Article


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