In most operation theaters today planning is done using pre- operatively gathered data, such as CT, MRI, or ultrasound (US). This data can become useless in cases such as lesion removal in brain, where dura opening and other preparations cause tissue shifting. A possibility to greatly increase accuracy in an ongoing operation is the use of 3D ultrasonography. The sequences of intra-operatively obtained 2D US-slices can be transformed into 3D, matched to previously acquired data, and be used to adapt the surgical planning to the current situation. The matching is done after standard image processing procedures have been applied to the 2D US data, this data has been injected into a 3D data cube, segmentation, and topological differentiation have taken place. This requires the usage of highly sophisticated graphics workstations. The objective is to create a framework in which surgeons and/or robotic neuronavigators can be informed and guided with the newest and most precise information possible during an operation.