CT-Based Orbital Volume Calculations Enable Endoscopic Transorbital Approach Planning in Pediatric and Adult Patients

Transorbital neuroendoscopic surgery (TONES) is increasingly utilized for skull base pathology in both adults and children. There remains limited data on orbital volume growth with age and its impact on the feasibility of TONES in young children. A thorough understanding of intraorbital anatomy is essential given its proximity to critical neurovascular structures. This work aims to develop a calculation of orbital volume based on high-resolution computed tomography (CT) scans to inform the working corridor size for patients of various ages and sizes in addressing lesions in different locations. To reliably calculate orbital volumes from thin cut bone window CTs, voxels greater than 300 Hounsfield units were selected to derive a skull mesh model for each patient. 5 landmarks were manually chosen for each orbit - 4 along the rim and 1 at the optic strut. The fast-marching algorithm mapped geodesic distance from each landmark along the mesh model. This enabled the calculation of the shortest path around the orbital rim. This was then repeated from the rim to the optic struct, defining the vertex set for the entire orbit. The convex hull of this set yielded the orbital volume for each patient ([ Fig. 1 ]). This orbital volume calculation was applied to CT scans from patients age 0-3, 4-7, 8-11 12-15, 16-18, and >18 years to model orbital growth, identify critical growth windows during pediatric craniofacial development, and integrate 3D modeling into transorbital approach selection. Fig. 1 Publication History Article published online: 27 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany