Merging visible and invisible: two Camera-Augmented Mobile C-arm (CAMC) applications

This paper presents the basic concept of Camera-Augmented Mobile C-arm (CAMC) and a set of its possible applications. A C C D camera is attached to a mobile C-arm uoroscopy X-ray system. Both optical and X-ray imaging systems are calibrated in the same coordinate system in an oo-line process. The new system is able to provide X-ray and optical images simultaneously. This system was rst used for on-line estimation of X-ray projection geometry for low cost mobile C-arms, which do not guarantee the reproducibility of their motion 8]. The CAMC framework has great potentials for medical augmented r eality. In this paper we introduce two new CAMC applications. They are quite diierent and could be s u b j e ct of two separate detailed papers for a medical conference. Here we only aim at brieey introducing these two new concepts to the Augmented R eality (AR) research community. The rst application aims at merging video images with pre-computed tomographic reconstruction of 3D volume of interest. This is a logical continuation of our work on 3D reconstruction using a CAMC 8]. The second approach is a totally new CAMC design where u sing a double mirror system and an appropriate calibration procedure the X-ray and optical images are m e r ged in real-time 1]. This new system enables the user to see optical image, X-ray image, or an augmented image where visible and invisible are c ombined i n r eal-time. The paper is organized in two more or less independent sections describing each of the above. Experimental results are p r ovided at the same time as the methods and apparatus are described for each section. 1 Overlay of pre-computed 3D reconstruction volume and optical images 1.1 Introduction Many clinical procedures are guided by X-r a y imaging: commonly under X-ray uoroscopy. Even if a 3D CT reconstruction is computed oo-line, often X-ray uoroscopy is used as interventional image-guided modality. However, the success of the procedure depends on the ability of the surgeon to mentally recreate the spatio-temporal intraoperative situation from two-dimensional uoroscopic X-ray images. Recently there has been a considerable eeort in replacing uoroscopic guidance with an interactive display o f 3 D b o n e m o d-els created from preoperative CT studies and tracked in real time 9, 3]. The basic motivation for proposing the Camera-Augmented Mobile C-arm (CAMC) in 8, 7] was to …