An ultrasound device(202) obtains an ultrasound image (218) in a scan plane (S) having a target area disposed therein. The device has disposed thereon a fiducial pattern (204), which includes first identifiers disposed in a region and second identifiers. A surgical device (206) has an image capture device (208) which captures a fiducial image of the pattern. A controller (212) receives the ultrasound image and the fiducial image and determines the position of the surgical device in relation to the scan plane based on the fiducial image. It identifies the first identifiers and the second identifiers by: applying a first threshold to the fiducial image substantially in parallel with applying a second threshold to an inverted fiducial image performing a connected component analysis on the first and second thresholds and applying a geometric filter to results of the analysis to identify the region having the first identifiers and to determine weighted centroids of the first identifiers and the second identifiers. A display (214) displays the ultrasound image (218) and a virtual image (206a) of the surgical device (206) in relation to the scan plane (S).
