Research On 3D Surface Reconstruction For The Gamma Knife Treatment Planning System

Gamma knife is an important instrument for the treatment of tumors by delivering a prescribed radiation dose to the target volume while minimizing the damage to surrounding healthy tissues. The key to improve the curative effect is to design a scientific treatment plan. The base of all treatment plan is to confirm the position of tumors and its relationships to patient's body contour and surrounding healthy tissues, so the 3D reconstruction of medical image is the important technical support. In traditional method, flat triangles produced by listed contour data are used directly to fit the surface in which the reconstructed effect and the expressive information are limited. A surface fitting algorithm adopting thrice triangular Bezier patch in the 3D reconstruction is proposed in this thesis. In shading phase, a quick Gouraud-Phong shading algorithm is proposed by integrating the quick processing of Gouraud algorithm with the normal interpolation idea of Phong algorithm. And based on the bilinear interpolation of normal vector in Phong algorithm, an improved quadric interpolation of normal vector is proposed in the Gouraud-Phong shading algorithm. A global smooth surface model can be gained when the quadric normal vectors are used in shading calculation.In order to observe the size and structure of inner tissues in 3D reconstruction, a 3D displaying model is proposed in this thesis. In details, the reconstruction model being cutted by a random plane , the textures being pasted on the sections are enriched to the doctors for more conveniently observing the relatively position of the tissues. The effect of this algorithm is similar to that of volume rendering, improving the rendering quality of 3D reconstruction.All these introduced are expected to be applied in the actual gamma knife treatment through further research.