Fig. 5.
Needle tip positioning studies. (a) Experimental setup (US probe removed to allow the needle to be seen in the images). (b) Position estimation of the needle tip and circle target. i. Images acquired and rectified based on the intrinsic camera parameters. ii. Image resolution increased 10x, and an ellipse detector used to segment circular targets (yellow dotted lines) and compute the centroids (yellow crosshairs). The needle is visible in both images (red dotted lines), allowing the needle tip to be extracted manually (red crosshairs).