Briton Riviere, Androcles and the Lion (1908) Auckland Art Gallery
I've been asked on a couple of occasions to localise a contraceptive implant that the referring doctors wanted to remove and had difficulty locating. I found this a bit difficult until I looked on google and found that the manufacturers had full and detailed instructions online. Here's one: http://www.implanonlocalization.com/ , with a comprehensive 18-page pdf manual, plus a couple of videos thrown in for good measure. It's obviously a bit of a problem if they've gone to all this effort. Ultrasound is the imaging method of choice. If this fails, they recommend MRI. I've not had to resort to MRI.