Modality-Independent Determination of Vertebral Position and Rotation in 3D

The determination of the position and rotation of vertebrae is important for the understanding of normal and pathological spine anatomy. Existing techniques, however, estimate the position and rotation parameters from two-dimensional (2D) planar cross-sections, are relatively complex and require a relatively large amount of manual interaction. We have developed an automated and modality-independent method for the determination of the position and rotation of vertebrae in three dimensions (3D) that is based on registration of image intensity gradients, extracted in 3D from symmetrical vertebral parts. The method was evaluated on 52 vertebrae; 26 were acquired by computed tomography (CT) and 26 by magnetic resonance (MR). The results show that by the proposed gradient-based registration of symmetrical vertebral parts, the position and rotation of vertebrae in 3D can be successfully determined in both CT and MR spine images. As the position and rotation of vertebrae in 3D are among the most important spine parameters, the proposed method may provide valuable support in the evaluation of deformities and disease processes that affect the spine.