Volumetric depth peeling for virtual arthroscopy

Three dimensional (3D) display of medical data sets is an increasingly useful tool. Viewing 3D reconstructions of objects from magnetic resonance imaging (MRI) and computerized tomography (CT) data is more natural and intuitive than mentally reconstructing these objects from orthogonal slices of the data, especially with the increase in size of datasets due to improving scanner resolutions. When displaying such data sets using volume rendering, appropriate selection of the transfer function is critical for determining which features of the data will be displayed. For virtual arthroscopy, however, no transfer function can enable views like that of a socket from within the ball of a joint because the ball itself blocks the view. Volumetric depth peeling (VDP) was developed to enable the rapid survey of joints for pathology by automatically culling occluding voxels, thus enabling textbook-like illustrations of joint surfaces that are not possible even with clinical arthroscopy (see Figure 1). VDP borrows conceptually from previous work, but is extended to the more general case of ray-based volume rendering, retaining full transfer-function control. Arthroscopy Arthroscopy is the process of inserting an arthroscope (a small camera) into a joint through an incision in the skin and so providing views of the interior of the joint. The technique is useful for diagnosing derangements within the joint and for performing surgery to treat them. However, arthroscopy is an expensive, invasive procedure that requires skilful manipulation of arthroscopic tools confined to the cramped spaces within joints. For preand post-operative diagnosis of joint derange