Fig. 3.

EM tracking in an MRI-US fusion scenario. US-to-EM reference frames calibration allow the EM navigation on the US. (a) The stylet is used to digitally reconstruct the applicator. The stylet path is lost halfway through the reconstruction of the inner channel of the ring, resulting in only half of the ring being reconstructed (as shown in the dotted-frame coronal view). (b) The 6 posterior transvaginal needles are reconstructed with the stylet, while the 3 anterior needles keep their preplanned positions until reconstruction. Those reconstructions are displayed in all three perpendicular views and fit on the US image. (c) The MRI contours are superimposed on the US image. Live tracking of the stylet inserted in the needle is shown by the red line (indicated by the white arrow), allowing to finely adjust the needles depth based on the target contour.