3D Assessment of Mandibular Growth Based on Image Registration: A Feasibility Study in a Rabbit Model

Abstract

Background. Our knowledge of mandibular growth mostly derives from cephalometric radiography, which has inherent limitations due to the two-dimensional (2D) nature of measurement. Objective. To assess 3D morphological changes occurring during growth in a rabbit mandible. Methods. Serial cone-beam computerised tomographic (CBCT) images were made of two New Zealand white rabbits, at baseline and eight weeks after surgical implantation of 1 mm diameter metallic spheres as fiducial markers. A third animal acted as an unoperated (no implant) control. CBCT images were segmented and registered in 3D (Implant Superimposition and Procrustes Method), and the remodelling pattern described used color maps. Registration accuracy was quantified by the maximal of the mean minimum distances and by the Hausdorff distance. Results. The mean error for image registration was 0.37 mm and never exceeded 1 mm. The implant-based superimposition showed most remodelling occurred at the mandibular ramus, with bone apposition posteriorly and vertical growth at the condyle. Conclusion. We propose a method to quantitatively describe bone remodelling in three dimensions, based on the use of bone implants as fiducial markers and CBCT as imaging modality. The method is feasible and represents a promising approach for experimental studies by comparing baseline growth patterns and testing the effects of growth-modification treatments.

Congenital and acquired mandibular asymmetry: Mapping growth and remodeling in 3 dimensions

“…30 The validity of using an automated, regional registration in the mandible to align longitudinal time points was evaluated in a rabbit model. 31 In this study, an affine Procrustes-based registration method was evaluated for accuracy against fiducial metallic implants, showing correspondence at less than 3 voxel widths. 31 Further studies in patients with Apert’s syndrome with clinical computed tomography data have shown method errors ranging from 0.4 to 0.8 mm for multiple landmarks.…”

“…31 In this study, an affine Procrustes-based registration method was evaluated for accuracy against fiducial metallic implants, showing correspondence at less than 3 voxel widths. 31 Further studies in patients with Apert’s syndrome with clinical computed tomography data have shown method errors ranging from 0.4 to 0.8 mm for multiple landmarks. 30 Some structures presumed to be stable in 2-dimensional projections, such as the mandibular canal, may show significant lateral displacement.…”

“…The method error was evaluated by repeating mandibular registrations and observations of growth; they showed a combined error of 1 mm or less using the Bland-Altman method. 29 Previous human 30 and animal model 31 studies have also shown that the errors of 3-dimensional (3D) mandibular registrations range from 0.3 to 1.0 mm with similar conditions and voxel sizes.…”

Comparison and reproducibility of 2 regions of reference for maxillary regional registration with cone-beam computed tomography

“…Promising animal studies on rat mandibles may be helpful to better understand 2D/3D differences 12 but the growth pattern in animal models may not be analogous to humans. Any shift of an area used as reference can cause a misinterpretation in the amount and direction of growth.…”

“…However, anatomical structures reported to be stable on lateral headfilm may not be reliable for 3D analysis that also involves the transverse dimension. 12 …”