Brachytherapy is the treatment method of choice for patients with a tumor relapse after a radiation therapy with external beams or tumors in regions with sensitive surrounding organs-at-risk, e. g. prostate tumors. The standard needle implantation procedure in brachytherapy uses pre-operatively acquired image data displayed as slices on a monitor beneath the operation table. Since this information allows only a rough orientation for the surgeon, the position of the needles has to be verified repeatedly during the intervention. Within the project Medarpa a transparent display being the core component of a medical Augmented Reality (AR) system has been developed. There, pre-operatively acquired image data is displayed together with the position of the tracked instrument allowing a navigated implantation of the brachytherapy needles. The surgeon is enabled to see the anatomical information as well as the virtual instrument in front of the operation area. Thus, the Medarpa system serves as 'window into the patient'. This paper deals with the results of first clinical trials of the system. Phantoms have been used for evaluating the achieved accuracy of the needle implantation. This has been done by comparing the output of the system (instrument positions relative to the phantom) with the real positions of the needles measured by means of a verification CT scan.
Marker-based optical tracking systems are often used to track objects that are equipped with a certain number of passive or active point markers. Fixed configurations of these markers, so-called rigid bodies, can be detected by, for example, infrared stereo-based camera systems, and their position and orientation can be reconstructed by corresponding tracking algorithms. The main issue in designing the geometrical constellation of these markers and their 3D positions is to allow robust identification and tracking of multiple objects, and this design process is considered to be an essential and challenging task. At present, the design process is based on trial-and-error: the designer constructs a marker configuration, evaluates it in a given setup, and rearranges the marker positions within the configuration if necessary. Even though single ready-made rigid bodies permit sufficiently good tracking, it is not ensured that the corresponding arrangements of markers meet any quality criteria in terms of reliability and robustness. Furthermore, it is unclear whether it is possible to add further rigid bodies to the setup which are sufficiently distinguishable from the given ones. In this paper, we present an approach to semi-automatically generate marker-based rigid bodies which are optimal with respect to the properties of the tracking system for which they are used, e.g., granularity, accuracy, or jitter. Our procedure which is aimed at supporting the design process as well as improving tracking generates configurations for several devices associated with an arbitrary set of point-based markers. We discuss both the technical background of our approach and the results of an evaluation comparing the tracking quality of commercially available devices to the rigid bodies generated by our approach.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.