ABSTRACT
The direct application of the two-dimensional shape measurements to three-dimensional objects is often difficult, incomplete, or ambiguous. When full three-dimensional measurements are performed on objects, such as a complete voxel array, some of the two-dimensional shape descriptors can be extended by analogy to three dimensions. An additional difficulty that affects all three-dimensional measurements, and especially any shape descriptors that depend on how well the surface of the object is defined, is the comparatively poor resolution that many three dimentional (3D) imaging methods provide. Voxels, the volume elements that comprise a 3D representation in the same way that pixels comprise one in two dimensional, are usually larger in both an absolute and relative sense than pixels. Registration is critical for image-based treatment planning and delivery, such as radiation treatment of tumors and robotic surgery. Although automatic registration is available, manual, visual-based image fusion using several orthogonal planar views is employed clinically to verify and adjust the automatic registration result.
