A variety of newer radiopharmaceutical agents are being developed, and many of these have already undergone clinical trials. Promising results have been reported with a two-step streptavidin-biotin approach. The unlabeled streptavidin is injected and allowed to localize through passive diffusion. Subsequently, the patient is injected with radiolabeled mIn-biotin, which is much smaller and has high binding affinity for streptavidin. Streptavidin-biotin imaging appears to be clinically useful for orthopedic and vascular graft infections. Advances in the understanding of the pathophysiologic mechanisms of diseases and the associated molecular biology may lead to exciting developments in radiotracers that target endothelial selectin receptors expressed in response to local inflammatory stimuli. In areas where positron emission tomography (PET) is available, 18F-fluoro-deoxyglucose (FDG) appears to be a sensitive technique.
All of the previous radiolabeling techniques fail to distinguish between bacterial-mediated infection and non-bacterial inflammation. Recently, 99mTc-Infecton, a novel ciprofloxacin based imaging agent, has been proposed to be specific for bacterial infection. In preliminary reports this agent has shown a sensitivity of 70% and a specificity of over 90% for detecting infective foci, with better imaging results than even radiolabeled leucocytes. False negative results were attributed to previous or current antibiotic treatment and/or infection with organisms that do not take up
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