Signal variation among adjacent slices (a–c) from an in vivo 3T FSE 3D IRON acquisition obtained in an ischemic rabbit hindlimb with two injection sites of SPION-labeled stem cells (250,000 dotted white arrow, 125,000 solid white arrow). Excellent background suppression leads to clear visualization of stem cell injection sites with positive contrast and a larger volume of hyperintense signal for the 250,000-cell injection site. The dashed white arrow indicates imperfections in both on-resonant water suppression and off-resonant fat suppression. (Reprinted with permission from43, 2007 John Wiley & Sons.)