How to recognize stent graft infection after endovascular aortic repair: the utility of 18F-FDG PET/CT in an infrequent but serious clinical setting

Objective To evaluate the diagnostic performance of 18 F-FDG PET/CT in the detection of stent graft infection (SGI). Methods In a retrospective study, two nuclear medicine physicians have independently analyzed 17 18 F-FDG PET/CT examinations performed for clinical suspicion of SGI. The images were evaluated for the uptake pattern and intensity, and by the maximum standard uptake value (SUV max ), the target-to-background ratio with blood pool (TBR BP ) and liver uptake (TBR hep ) as a reference. The SGI was defined as the presence of focal hyperactivity with an intensity exceeding hepatic uptake. CT images were independently assessed for signs of SGI. Clinical review of all further patients’ data served as the standard of reference. Results Nine cases were established as SGI by the clinical review. PET/CT correctly diagnosed SGI in eight and yielded a sensitivity of 89% and specificity of 100%. The mean SUV max , TBR BP, and TBR hep values were 9.8 ± 4.0, 6.9 ± 2.6, and 4.6 ± 1.7 in the group of patients with true SGI, and 4.0 ± 1.1, 2.5 ± 0.4 ( p < 0.001) and 1.9 ± 0.2 ( p < 0.001) in true negative cases, respectively. CT alone showed a sensitivity of 78% and specificity of 100% and was concordant with PET/CT in 14 cases. The best performing threshold values of SUV max , TBR BP , and TBR hep were 5.6, 3.5, and 2.2, respectively. Conclusion 18 F-FDG PET/CT with expert evaluation, semiquantitative and quantitative image analysis with the proposed threshold values for SUV max , TBR BP , and TBR hep has good diagnostic accuracy in the detection of SGI. We propose that visual grading scale for SGI should use hepatic uptake as a visual reference.