Which is the optimal acquisition time for FDG PET/CT imaging in patients with infective endocarditis?

Prosthetic valve endocarditis is a pathological condition accounting for 20%-30% of all infective endocarditis (IE) episodes.1 In some patients both with and without valvular prostheses, the main issue for transthoracic echocardiography (TTE) or trans-esophageal echocardiography (TEE) is the difficult differential diagnosis between septic and aseptic vegetations. Recently, combined positron emission tomography and computed tomography (PET-CT) with 18F-flurodeoxyglucose (FDG) has emerged as a valuable tool for the diagnostic work-up of infectious diseases as well as in IE showing considerable promise in this clinical setting.2-4 All the studies conducted so far adopted the ‘‘standard’’ PET-CT protocol which is routinely used for oncological purposes consisting in 6-hour fasting and PET imaging performed 60 ± 10 minutes after FDG injection. As intracardiac septic foci can be very small, around the spatial resolution of PET system (4-6 mm), and mostly located in areas with high background activity, an adequate patient preparation to suppress myocardial background activity as well as a delayed PET-CT imaging could increase the diagnostic accuracy of this technique maximizing the contrast between septic foci and background. The following is a case example of the higher diagnostic sensitivity of delayed FDG PET/CT imaging.