Targeted Bacteria-Specific 18F-Fluoro-Maltohexaose But Not FDG PET Distinguishes Infection From Inflammation

Learning Objectives: On successful completion of this activity, participants should be able to (1) understand the role of 18 F-FDG PET/CT for diagnosis of cardiovascular device infection, as a functional imaging tool for assessing the overall host-pathogen immune response in infection; (2) learn about the strengths and limitations of bacteria-targeting radiotracers for infection imaging, including those based on substances of bacterial maltodextrin transporters, bacterial thymidine kinase, antibiotics, antimicrobial peptides, antibacterial antibodies, bacteriophages, and bacterial DNA/RNA hybrid nucleotide oligomers; and (3) discuss the pros and cons of 18 F-FDG versus bacteria-targeting tracers. Financial Disclosure: The authors of this article have indicated no relevant relationships that could be perceived as a real or apparent conflict of interest. CME Credit: SNMMI is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to sponsor continuing education for physicians. SNMMI designates each JNM continuing education article for a maximum of 2.0 AMA PRA Category 1 Credits. Physicians should claim only credit commensurate with the extent of their participation in the activity. For CE credit, SAM, and other credit types, participants can access this activity through the SNMMI website (http://www.snmmilearningcenter.org) through March 2023. Rapid and accurate diagnosis of cardiovascular device infection remains a challenge in the clinic. Anatomic imaging tools such as echocardiography and cardiac CT or CT angiography are the firstline modalities for clinically suspected endocarditis given their ability to detect vegetation and perivalvular complications. Accumulating data suggest that functional imaging with 18 F-FDG PET/CT has unique merits over anatomic imaging and could potentially diagnose early cardiac device infection before morphologic damage ensues and identify infection sources or bacterial emboli in the rest of the body. Although an abnormal finding on 18 F-FDG PET/CT was added to the 2015 guidelines of the European Society of Cardiology as a major criterion for the diagnosis of device-related and prosthetic valve endocarditis, that addition has not been incorporated in the U.S. guidelines. Beyond these clinically available imaging tools, attempts have been made to develop bacteria-targeting tracers for specific infection imaging, which include tracers of bacterial maltodextrin transporter, bacterial thymidine kinase, antibiotics, antimicrobial peptides, bacterial antibodies, bacteriophages, and bacterial DNA/RNA hybrid nucleotide oligomers. Most of the tracers have been studied only in experimental animals, except for radiolabeled antibiotics, which have been examined in humans without success in clinical translation for infection imaging. In this article, we compare the roles of anatomic and functional imaging for cardiac device infection and discuss the pros and cons of 18 F-FDG and bacteria-targeting tracers. While anticipating continued investigations for bacteria-specific...

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