Quantitative Analysis of a Three-Dimensional Computed Tomography Image Rendering Protocol for Skull Base Applications

Abstract

Objective: Three-dimensional (3D) volume-rendering image protocols are being utilized at our institution in the development of virtual surgical simulators for improving surgical planning and predicting operative exposures in complex skull base surgery. Image reconstruction protocol validation is essential to verify the accuracy and precision needed for clinical applications. Methods: Three cadaver heads were examined using fine-cut CT. Archived data were transferred to a workstation and, using a 3D visualization and modeling system, high-resolution 3D-CT volumetric reconstructions of the skull base were generated using a specific voxel threshold protocol. Based on conventional craniometric and skull base anatomical landmarks (n = 20), linear anthropomorphic distances (n = 20) were measured on 3D-CT reconstructions. Subsequently, soft tissues were removed from the cadaver heads and linear measurements were repeated manually using digital calipers. All measurements were taken three times, independently, yielding 120 total measurements. Results: No statistically significant difference (p > 0.01) was found between 3D-CT reconstruction and physical cadaver measurements for 19 of 20 linear distances (95%). 3D-CT volumetric reconstructions overestimated one anthropomorphic measurement (glabella to left porion; p = 0.0095) repeatedly. Conclusions: 3D-CT volume-rendered images of the skull base generated using our voxel threshold protocol is both accurate and precise. Virtual 3D skull base models generated using this protocol represent true skull base anatomy. This study represents an essential first step toward the development of a validated and accurate 3D surgical approach assessment model and skull base surgical simulator currently under development at our institution.