Feature points analysis for quantitative evaluation of 3D mandibular shape using 2D cephalograms

Abstract

This study discusses mandibular-shape features specified on two-dimensional (2D) cephalograms and three-dimensional (3D) CT volumes. The feature points were specified on cephalograms with a house-developed software. Then, the points on frontal and lateral cephalograms were projected into the 3D space, which we had calibrated the imaging coordinate systems, and given 3D geometries. The calibration corrected geometrical incorrespondence between ear pads on the frontal and lateral images. The 3D point reconstruction was done considering projection scaling. In addition, 3D feature points were specified on the CT volumes. Then, we compared these three-type feature point sets for each mandibular landmark and tried to give them some clinical meanings. Comparison among the three point sets resulted that the 3D reconstruction with projection worked well and correctly provided the 3D geometries of feature points. As well, the difference between the 2D and 3D points showed some trends relative to the curvature of bone surfaces.