Molecular Imaging Techniques in the Diagnosis and Monitoring of Infectious Diseases

Combined positron emission tomography and computer tomography with 2-deoxy-[fluorine-18]-flouro-D-glucose ([¹⁸F]FDG-PET/CT) is increasingly used in suspected infection and inflammation. Evidence is mounting within several areas. We believe [¹⁸F]FDG-PET/CT is a key modality in infection and inflammation and this overview outlines the diagnostic values in most common uses within this domain.

[¹⁸F]FDG-PET/CT is considered helpful in establishing the underlying disease in 50–60% of FUO patients. In patients with complex blood stream infections, [¹⁸F]FDG-PET/CT changes treatment and reduces relapse rates and mortality—if scans are negative prognosis is favorable and it may be safe to withhold or de-escalate treatment strategy. In infectious endocarditis, [¹⁸F]FDG-PET/CT has an impact in prosthetic valve endocarditis and cardiovascular implantable electronic devices whereas its diagnostic use in NVE is limited. In spondylodiscitis, [¹⁸F]FDG-PET/CT and MRI have overall equally and complementary diagnostic performance with combined sensitivity and specificity of ~ 100%. In vascular graft infections, [¹⁸F]F DG-PET/CT is highly sensitive (> 90%) with a high negative predictive value, whereas false positive findings are challenging, especially early post-operative. Leucocyte scintigraphy combined with bone marrow scintigraphy has a better overall accuracy compared to [¹⁸F]FDG-PET/CT in suspected hip and knee prosthetic joint infections, but several practical issues favor [¹⁸F]FDG-PET/CT. Future developments of more specific tracers and novel scanner technology holds potential.

Evidence for [¹⁸F]FDG-PET/CT in infectious and inflammatory disease supports the use in fever of unknown origin, bloodstream infections, spondylodiscitis, infective endocarditis, vascular graft infections, and prosthetic joint infections. However, the literature is generally heterogeneous and several issues remain unclarified, e.g., patient selection and interpretation criteria. [¹⁸F]FDG-PET/CT has a definite role in infectious and inflammatory imaging, but firm evidence is still lacking on its precise place in the diagnostic pathways.