The future of infection imaging.

Over the past 10 years, there has been an unprecedented explosion in new agents suggested for imaging infection. These agents have been based on our understanding of the processes involved in invasive infection of the body by microorganisms and the body's response to them. Work with antibodies has traditionally yielded the most likely candidates, 3 of which have entered clinical use in Europe and the USA. However, the expense and limitations of producing antibodies have resulted in investigations into the use of cytokine and anti-microbial radiolabelled peptides. This work is very promising in that these types of tracers may be more specific for infection than labelled leukocytes. There remains a big question mark, however, as to whether or not these will progress from phase I/II trials to phase III trials and, ultimately, to clinical use. Finally, the investigation of radiolabelled anti-microbials continues and may prove to be most useful with anti-fungals especially in the immuno-suppressed host. We live in exciting times in the evolution of infection imaging; time and commercial constraints will determine which, if any of these tracers make it to the market and will they do so before PET rules all nuclear medicine?