FDG PET/CT and WBC scan in vascular graft infection

Introduction: there are few studies comparing [18F]FDG-PET/CT and scintigraphy with 99mTc-HMPAO-WBC in the diagnosis of vascular prostheses infections. Moreover, the distribution patterns of FDG and of radiobelled-WBC in patients with endoprosthesis, in relation to the type of stent and time from surgery, is not know. Aim: to compare [18F]FDG and 99mTc-HMPAO-WBC in patients operated with vascular endoprosthesis Endurant® and to define the patterns of normality and abnormality for both radiopharmaceuticals. Materials & Methods: 16 patients, that underwent an endovascular exclusion of abdominal aneurysm with Endurant® endoprostheses, were retrospectively enrolled in the study. Half of patients had suspicion of infection (based on CT, ESR, GB, PCR, fever), half were clinically and biochemically infection free and were operated 8-41 months before. Each patient performed both scans. For WBC: dynamic images were acquired on the abdomen in the anterior-posterior from time 0 to 2.5 minutes (one frame every 4 seconds for 40 frames). Planar images were acquired on the abdomen in antero-posterior and oblique front left and right. The first set of images was acquired 10 minutes after administration of WBC (100 seconds acquisition time), the second set at 3h (141 seconds acquisition), the third set at 20h (1040 seconds acquisition). For PET: images were acquired 1h after administration of 185 MBq [18F]FDG. All images were examined by 2 independent physicians. Qualitative analysis was performed for WBC scans and both qualitative and semi-quantitative analysis (SUVmax and SUVmaxT/SUVmeanBKG) was performed for PET scans. Final diagnosis was made by clinical-surgical follow-up. Results: no patients of first group had an infection but 5 of second group were infected. All patients but 1 were correctly identified using the following interpretation criteria: for WBC scan, positivity for infection is represented by the accumulation of radioactivity with time in the peri-prosthetic tissue; negativity for infection was consistent with no uptake in peri-prosthetic tissues; for FDG-PET/CT, positivity was characterized by an inhomogeneous intra- and extra-vascular uptake with a SUVmax≥3.6 and a SUVmaxT/SUVmeanBKG>3.0; negativity was considered an homogeneous uptake with an SUVmax