Faculty of Electrical Engineering, University of Ljubljana, Trzaska 25, SI-1000 Ljubljana, Slovenia.
Phys Med Biol. 2011 Dec 7;56(23):7505-22. doi: 10.1088/0031-9155/56/23/011. Epub 2011 Nov 11.
Accurate and objective evaluation of vertebral deformations is of significant importance in clinical diagnostics and therapy of pathological conditions affecting the spine. Although modern clinical practice is focused on three-dimensional (3D) computed tomography (CT) and magnetic resonance (MR) imaging techniques, the established methods for evaluation of vertebral deformations are limited to measuring deformations in two-dimensional (2D) x-ray images. In this paper, we propose a method for quantitative description of vertebral body deformations by efficient modelling and segmentation of vertebral bodies in 3D. The deformations are evaluated from the parameters of a 3D superquadric model, which is initialized as an elliptical cylinder and then gradually deformed by introducing transformations that yield a more detailed representation of the vertebral body shape. After modelling the vertebral body shape with 25 clinically meaningful parameters and the vertebral body pose with six rigid body parameters, the 3D model is aligned to the observed vertebral body in the 3D image. The performance of the method was evaluated on 75 vertebrae from CT and 75 vertebrae from T(2)-weighted MR spine images, extracted from the thoracolumbar part of normal and pathological spines. The results show that the proposed method can be used for 3D segmentation of vertebral bodies in CT and MR images, as the proposed 3D model is able to describe both normal and pathological vertebral body deformations. The method may therefore be used for initialization of whole vertebra segmentation or for quantitative measurement of vertebral body deformations.
准确客观地评估椎体变形对于脊柱病变的临床诊断和治疗具有重要意义。尽管现代临床实践主要集中在三维（3D）计算机断层扫描（CT）和磁共振（MR）成像技术上，但评估椎体变形的既定方法仅限于在二维（2D）X 射线图像中测量变形。在本文中，我们提出了一种通过 3D 中椎体的高效建模和分割来定量描述椎体变形的方法。通过引入变换来评估变形，这些变换可以更详细地表示椎体形状，从而对 3D 超二次模型的参数进行评估。该模型将椎体形状建模为 25 个具有临床意义的参数，并将椎体姿势建模为 6 个刚体参数，然后将 3D 模型与 3D 图像中观察到的椎体对齐。该方法在 CT 上的 75 个椎体和 T2 加权 MR 脊柱图像上的 75 个椎体上进行了评估，这些椎体取自正常和病理脊柱的胸腰椎部分。结果表明，该方法可用于 CT 和 MR 图像中椎体的 3D 分割，因为所提出的 3D 模型能够描述正常和病理椎体的变形。因此，该方法可用于整个椎体分割的初始化或椎体变形的定量测量。
