bungler, good question for the immunogenetic engineers. BaviImaging would have to have a "label" and form an image for recording the parameters of size, shape, metabolic activity, and the presence of other specially propitious docking sites/targets on tumor. I saw somewhere in the literature that Bavi loses some specificity for the -PS docking site when both arms are not free to dock [way oversimplified], but that seems a "fixable" issue which has probably already been accomplished. It is possible that the "therapeutic" arm to be amputated might, in fact, be carrying a "contrast agent". Magnetic imaging-like modalities and PET-like applications could be used to locate Bavi-in-the-body. Hope this elicits the real answer for you Bungler.