Voxel‐based superimposition of serial craniofacial CBCTs: Reliability, reproducibility and segmentation effect on hard‐tissue outcomes

Abstract

To test the reliability and reproducibility of a fast and user-friendly voxel-based 3D superimposition method and the effect of bone segmentation on its outcomes. This prospective methodological study assessed 15 pairs of pre-existing serial CBCT images (interval: 1.69±0.37years) obtained from growing patients (initial age: 11.75±0.59years). Volumes were superimposed on the anterior cranial base using Dolphin 3D software. Reliability was assessed visually, by inspecting the overlap of the superimposition reference structures. Reproducibility was tested with intra- and inter-operator comparisons of superimposition outcomes. The method presented good reliability in all cases. The median differences between intra- and inter-operator comparisons at various tested areas ranged from 0.06 to 0.16mm and from0.15 to 0.24mm, respectively. In few individual cases, differences exceeded 0.5mm. There was no evidence that the error increased upon increase in the magnitude of the detected T0-T1 changes. However, the superimposition error increased when the distance between the measurement area and the superimposition reference also increased. For a single image, the median error of bone surface segmentation ranged in different areas between 0.05 and 0.12mm, with few exceptions where it slightly exceeded 0.25mm. The tested voxel-based superimposition method presented good efficiency, cranial base matching and reproducibility in a growing patient sample. Segmentation error was considered minimal. The total error reached clinically relevant levels in very few cases. Thus, this technique is considered appropriate for clinical use, when 3D assessment of craniofacial changes is required.