Planning of needle positions is based on a 2D image data visualization module where multiple needle insertion trajectories can be planned (Figure 3a). Image data is imported from the available imaging system and displayed on the navigation screen. Through a touch-screen interface the user defines the needle trajectory by selecting a target (e.g. tumor) and an additional needle entrance position at the surface of the patient body, as visible on the available CT images.
Anatomy Overview Guidance
Before each needle insertion the appropriate trajectory is selected. Initially, i.e. when the needle tip is far from the planned entry point, a 3D viewer, showing a 3D model of the patient abdomen together with the selected trajectors is displayed. Single markers are color-coded according to the amplitude of deformation at this point. The lower part of the screen shows the tracking error averaged over all markers.
When the needle tip is close to the planned entry point, the targeting viewer is displayed. It displays a projection of the needle tip (red dot) and shaft (green dot) within a cross-hair guiding system. Needle depth is represented by a vertical scale. The needle alignment with the planned trajectory is achieved by aligning both the tip and shaft in the center of the cross-hair. The viewer on the right-hand side displays the image slice along the current needle axis and enables the user to visualize the structures close to the trajectory.