The aim of this study was to investigate the diagnostic yield of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) for detecting thoracic aortic graft infection (AGI) in comparison to expert consensus MAGIC criteria.

Patients suspected clinically of having thoracic-AGI were prospectively recruited. Consensus MAGIC criteria for AGI were compared to findings on FDG PET imaging. MAGIC criteria were verified against clinical/surgical, radiological, and microbiological/laboratory predefined major and minor parameters. FDG images were interpreted using a semiquantitative visual grading score (VGS, abnormal ≥ 3), focal uptake and quantitative maximum standard FDG uptake value (SUV_max, abnormal ≥ 7.3), and target-to-background FDG ratio (TBR_max, abnormal ≥ 4.2).

Of 35 patients suspected of having thoracic-AGI, MAGIC diagnostic criteria were positive for AGI in 25 patients (71%) and negative in 10 (29%). FDG PET imaging was abnormal in 27 patients (77%). Abnormal and normal FDG imaging findings were concordant with MAGIC criteria in 31 patients (88.6%). In 4 patients, FDG imaging results were discordant with MAGIC criteria. By ROC analysis, optimal FDG cut-off values for detecting AGI by MAGIC were ≥ 3 for VGS, ≥ 7.3 for SUV_max and ≥ 4.2 for TBR_max, with concordance with MAGIC criteria in 88.6%, 85.7%, and 88.6% of patients, respectively. Two or more FDG imaging parameters (VGS, focal uptake, SUV_max, and TBR_max) yielded highest diagnostic concordance of 91.4%. VGS inverse odds ratio for AGI was 7.14. In 4 of 6 selective patients who had repeat FDG PET imaging during antibiotic treatment, quantitative FDG imaging values improved over time with associated improvement of laboratory markers of inflammation.

FDG PET/CT imaging, using (semi-)quantitative imaging parameters, showed high concordance with expert consensus MAGIC criteria for AGI. These data suggest a potential complementary role of quantitative FDG/CT imaging, not only to detect AGI, but also to monitor response to antibiotic treatment.