Augmenting mobile C-arm fluoroscopes via stereo-RGBD sensors for multimodal visualization

Fusing intraoperative X-ray data with real-time video in a common reference frame is not trivial since both modalities have to be acquired from the same viewpoint. The goal of this work is to design a flexible system comprising two RGBD sensors that can be attached to any mobile C-arm, with the objective of synthesizing projective color images from the X-ray source viewpoint. To achieve this, we calibrate the RGBD sensors to the X-ray source with a 3D calibration object. Then, we synthesize the projective color image from the X-ray viewpoint by applying a volumetric-based rendering method. Finally, the X-ray image is overlaid on the projective image without any further registration, offering a multimodal visualization of X-ray and color images. In this paper we present the different steps of development (i.e. hardware setup, calibration and rendering algorithm) and discuss clinical applications for the new video augmented C-arm. By placing X-ray markers on a hand patient and a spine model, we show that the overlay accuracy between the X-ray image and the synthetized image is in average 1.7 mm.