Geometrical measurements of orthognathic surgery change using cone beam computed tomography

Abstract

Imaging in the three dimensional format, Cone Beam Computed Tomography has become quite popular in orthodontics. Tools for analyzing the volumetric data however have not caught up with the recent industry demands. Most of the analysis in 3D is primarily based on techniques used in 2D format, thus adding some limitations to the post diagnostic capabilities of the imaging modality. Currently there is no dedicated tool or a stand-alone automated technique to capture the geometry of the CBCT volumes. The purpose of this study is to explore a method to measure the geometry of the CBCT volumes and find the changes in the orthodontics after the surgery, all in a technically non-intensive and reproducible way, thereby paving way for further developments of dedicated analysis tools in this field.

Anonymized sequential CBCT volumes of subjects prior to and after the surgery were obtained from the University of Tampere Hospital’s radiology department. The volume sets of the subjects were loaded into AMIRA software tool, resampling if the volumes were not of similar dimensions, superimposed with mutual information algorithm, segmenting required volumes for 3D rendering, attaching landmarks to specific locations and measuring the geometries from the landmarks. The method was then put into a step by step guide with minimum technical knowhow for usage by the medical personnel.