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

Prosthetic valve endocarditis is a pathological condition\r\naccounting for 20%-30% of all infective\r\nendocarditis (IE) episodes.1 In some patients both with\r\nand without valvular prostheses, the main issue for\r\ntransthoracic echocardiography (TTE) or trans-esophageal\r\nechocardiography (TEE) is the difficult differential\r\ndiagnosis between septic and aseptic vegetations.\r\nRecently, combined positron emission tomography and\r\ncomputed tomography (PET-CT) with 18F-flurodeoxyglucose\r\n(FDG) has emerged as a valuable tool for the\r\ndiagnostic work-up of infectious diseases as well as in IE\r\nshowing considerable promise in this clinical setting.2-4\r\nAll the studies conducted so far adopted the ‘‘standard’’\r\nPET-CT protocol which is routinely used for oncological\r\npurposes consisting in 6-hour fasting and PET imaging\r\nperformed 60 ± 10 minutes after FDG injection. As\r\nintracardiac septic foci can be very small, around the\r\nspatial resolution of PET system (4-6 mm), and mostly\r\nlocated in areas with high background activity, an\r\nadequate patient preparation to suppress myocardial\r\nbackground activity as well as a delayed PET-CT imaging\r\ncould increase the diagnostic accuracy of this technique\r\nmaximizing the contrast between septic foci and background.\r\nThe following is a case example of the higher\r\ndiagnostic sensitivity of delayed FDG PET/CT imaging.