Distinguishing Active Vasculitis From Sterile Inflammation and Graft Infection: A Call for a More Specific Imaging Target.

F luorine-18-fluorodeoxyglucose (FDG) is an indicator of vascular macrophage or leukocyte burden that has been reported in atherosclerosis, infection, large-artery vasculitis, chemotherapyor radiation-induced vascular inflammation, and foreign-body reaction (1). FDG positron emission tomographic (PET) imaging may detect early phases of large-artery vasculitis before progression to arterial narrowing ensues. However, once the diagnosis of large-artery vasculitis, such as Takayasu’s arteritis, is established and patients are treated with arterial bypass graft surgery, the reliability of FDG PET metabolic signal for differentiating recurring or partially treated disease activity from foreign-body reaction at the graft surgery site remains challenging. Unrecognized vasculitis or graft infections that are treated late carry high mortality rates. Identifying early phases of vasculitis is critical for timely initiation of immunosuppressive therapy and prevention of arterial stenosis, perianastomotic dilatation, and aneurysm. Identifying infection early can facilitate antibiotic therapy or graft revision and thus forestall suppurative complications. In contrast, mistaking infection for disease recurrence and instituting immunosuppressive therapy might be disastrous, or making amistake the other way around alsomay result in additional imaging studies, delayed therapy, or unnecessary surgery. As such, high specificity for vasculitis