"You asked about the development of imaging agents. Here antibodies have been linked to iron particles that can be detected by MRI. This can detect white blood cells. Which in principle this looks good, there may be practical limitations for human application. First the MRI does not have the resolution to be able to detect single cells and so all this will see are cell clumps and second because it is protein/antibody based there is a chance that the person could make anti-globulin responses and so on second application it may get an allergic reaction."