We have developed an image fusion module for combined 3D ultrasound and MRI/CT visualization in image-guided neuronavigation. The module demonstrates alternative image visualization possibilities, which might be integrated in future ultrasound-based neuronavigation systems. The image fusion visualization module reads 3D ultrasound, MRI/CT image data sets and patient registration information which are saved during the operation using the SonoWand ultrasound-based neuronavigation system earlier presented by our group [1]. The images are visualized simultaneously in the same scene by overlay, compositing or splitting visualization techniques which makes perception of information easier as compared to visualizing images in different scenes. Quantitation of brain shift between similar structures recognized in both preoperative MRI and intraoperative ultrasound images was done using both a manual and an automatic image processing algorithm. The results show that alternative image visualizations may be useful in order to get immediate feedback regarding brain shift in the early beginning of the operation. The present paper summarizes the experiences gained using this visualization module on patient image data acquired in our clinic during the last year using the SonoWand ultrasound-based neuronavigation system.