Improving İnfective Endocarditis Diagnosis by Combining Semi-Quantitative and Visual Findings Obtained from F-18 FDG PET/CT Imaging

OBJECTIVE
Assess visual and semi-quantitative outputs of F-18 FDG PET/CT for diagnostic purposes in infective endocarditis (IE), and determine whether increased spleen/bone marrow FDG uptake secondary to infection can be used in the diagnosis of IE.


METHODS
Patients with F-18 FDG PET/CT examinations for a preliminary diagnosis of IE (July 2020–January 2024) were analyzed. IE diagnostic criteria was used to confirm diagnoses to create the IE-positive group and the control group (IE excluded). Demographics and imaging-related data (SUVmean and/or SUVmax for lesion, liver, spleen, and lumbar vertebrae) were recorded. Spleen hypermetabolism and bone marrow hypermetabolism (BMH) were defined respectively in patients with spleen/liver or bone marrow/liver ratios exceeding 1. Visually-assessed FDG uptake was scored from 0 to 3, creating the uptake score, which was dichotomized to create low and high uptake groups.


RESULTS
There were 48 IE and 21 control patients. Lesion SUV, uptake score, spleen hypermetabolism, and BMH revealed significant differences among groups. For the distinction of IE, high uptake score had a sensitivity of 85.42% and overall accuracy of 84.06%, while lesion SUVmax (>3.5) had the highest specificity (95.24%) and the highest positive predictive value (96.77%).


CONCLUSION
Visual detection of uptake exceeding blood pool value with F-18 FDG PET/CT images and presence of a SUV value of >3.5 appear to distinguish IE patients with high accuracy. Additionally, IE was more likely in the presence of increased bone marrow FDG uptake.