A-043 16 Vascular grafts replace occluded vessels to maintain patency. Although rare (1-6%), graft infections are severe surgical complications, with poor prognosis. Optimal treatment of infected grafts is surgical removal. The challenging question affecting management is whether the graft or only adjacent soft tissue wound is infected. False positives lead to unnecessary surgery while false negatives are associated with high morbidity. SPECT and PET radiopharmaceuticals are used for diagnosis of vascular graft infection. Labelled leucocytes (Tc-99m, In-111) are SPECT agents of choice, accumulate by diapedesis, chemotaxis and vascular permeability. False-negative studies are related to antibiotherapy or duration of symptoms, and false positives occur with lymphocelle, haematoma, thrombosis, and physiologic uptake in recent grafts. FDG, the main PET tracer, is taken up by infections with high cellular metabolism. Advantages of PET over SPECT imaging include lower background activity, shorter duration of studies and no handling of blood of potentially infected patients. False positives due to increased uptake in native vessels, early grafts or healing scars can be differentiated by pattern and intensity of uptake. Size and proximity of structures and positional changes can lead to inaccurate localisation of tracer-avid foci and faulty diagnosis. Combining anatomic CT landmarks with functional SPECT changes or increased metabolism on PET decrease the false-positive rate. Uptake foci are accurately localised to graft or soft tissues improving specificity and diagnostic accuracy. SPECT/CT provided accurate data for diagnosis and localisation in 67% of patients and accuracy of FDG-PET/CT was above 95% for diagnosis of vascular graft infection. Learning Objectives: 1. To understand the potential value of nuclear medicine procedures in suspected vascular graft infection. 2. To understand the specific incremental role of hybrid imaging in suspected vascular graft infection. 3 . To recognise patterns of true and false positive findings in infected vascular grafts and to know the referral criteria for the best utilisation of hybrid imaging in vascular graft infection. 