1. A method of fusing a real-time ultrasound (US) image with a segmented pre-acquired image of another modality, the pre-acquired image including a test location, the real-time US image including the test location, the method comprising: obtaining the real-time US image; manually or automatically selecting a point cloud in the real-time US image; with a computer processor, transforming the US image of the test location to a coordinate system of a tracking system; with the computer processor, transforming the test location from the coordinate system of the tracking system to a coordinate system of the pre-acquired image; with the computer processor, matching the point cloud to a surface segmentation of the segmented pre-acquired image; with the computer processor, registering the real-time US with the segmented pre-acquired image; and displaying the pre-acquired image and the real-time US image of the test location in the coordinate system of the pre-acquired image.