Real-time virtual bone drilling for haptic surgical simulation

Abstract

This thesis aims to provide a real-time bone-drilling simulation with haptic feedback for comprehensive dental implant surgery training. The present study discusses real-time approaches for visualization of sequential bone removal, stable haptic feedback during the drilling or probing of bone, and consistent haptic feedback during and after bone drilling. To generate realistic haptic feedback for bone drilling, we control the bone removal rate and the magnitude and amplitude of drilling vibration. Although this study is primarily concerned with the simulation of bone drilling, this study can also be applied to other studies such as those on machining simulation or virtual sculpting. Bone is represented by volume data (bone volume) in a three-dimensional discrete regular grid so as to visualize sequential bone removal. Each voxel has a density property that describes the degree of bone removal. Whenever a drill collides with bone voxels, their density values decrease. Collision detection between the bone volume and the drill is performed accurately using a bounding sphere and a signed distance field of the drill bit. A triangular mesh is extracted from the volume data using a surface reconstruction algorithm and is displayed via a graphics rendering pipeline. A contact force between the bone and drill is resolved by a penalty-based point-contact model. A point shell covers voxels on the bone surface. An approximated normal vector generated from the bone volume is assigned to each point shell point. Point shell points track the modification of the bone volume; if a voxel of the bone volume is cut out, the point shell point for this voxel is removed, and a boundary-fill algorithm is applied to cover the hole of the point shell. When a point shell point is in collision with the drill bit (i.e., the queried distance value is negative), a penalty force is computed. We approximately compute the contact force by summing all penalty forces for the colliding point sh...