18F-Fluorodeoxyglucose positron emission tomography/CT scanning in diagnosing vascular prosthetic graft infection

Abstract

Vascular prosthetic graft infection (VPGI) is a severe complication after vascular surgery. CT-scan is considered the diagnostic tool of choice in advanced VPGI. The incidence of a false-negative result using CT is relatively high, especially in the presence of low-grade infections. (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG PET) scanning has been suggested as an alternative for the diagnosis and assessment of infectious processes. Hybrid (18)F-FDG PET/CT has established the role of (18)F-FDG PET for the assessment of suspected VPGI, providing accurate anatomic localization of the site of infection. However, there are no clear guidelines for the interpretation of the uptake patterns of (18)F-FDG as clinical tool for VPGI. Based on the available literature it is suggested that a linear, diffuse, and homogeneous uptake should not be regarded as an infection whereas focal or heterogeneous uptake with a projection over the vessel on CT is highly suggestive of infection. Nevertheless, (18)F-FDG PET and (18)F-FDG PET/CT can play an important role in the detection of VPGI and monitoring response to treatment. However an accurate uptake and pattern recognition is warranted and cut-off uptake values and patterns need to be standardized before considering the technique to be the new standard.

Figure 1

Coronal and axial view of fused ¹⁸F-FDG PET/CT images. In this particular case, a 67-year-old male patient underwent an aorto-bi-iliac bypass 16 years ago. After 3 years the bypass was revised because of an occlusion. Five years later the second bypass also occluded and an axillobifemoral bypass was constructed. Unfortunately this bypass also occluded twice. Patient is admitted to the hospital because of pain and redness at the level of the axillobifemoral bypass probably due to infection. ¹⁸F-FDG PET/CT scanning showed increased FDG uptake at the level of both occluded bypasses, the aorto-bi-iliac bypass and the axillobifemoral bypass. Arrows are pointing at increased FDG uptake in both bypasses. Ultimately, no bacteria were cultured.

Figure 2

Coronal view of fused ¹⁸F-FDG PET/CT image of a culture proven not infected vascular prosthetic graft. In this particular case, a 45-year-old male patient underwent emergency surgery by placement of a Viabahn in the left common iliac artery because of rupture. He was admitted to the hospital 6 weeks later with fever and sepsis. ¹⁸F-FDG PET/CT scanning showed increased FDG uptake at the level of the left iliac artery. Ultimately, no bacteria were cultured from the graft under antibiotic therapy.

Figure 3

Coronal view of a fused ¹⁸F-FDG PET/CT image of a culture proven infected vascular prosthetic graft. In this particular case, a 70-year-old male patient underwent an ileofemoral bypass from the left to right side using Dacron. After 10 years the patient was readmitted with an occlusion of the bypass possibly due to a suture aneurysm. CT scan revealed an occlusion of the bypass with no signs of infection. ¹⁸F-FDG PET/CT scanning clearly showed increased FDG uptake at the level of the suture aneurysm. Ultimately, Escherichia coli were cultured from the graft.

Figure 4

Axial view of a CT scan and fused ¹⁸F FDG PET/CT image of a culture proven infected vascular prosthetic graft. In this particular case, a 67-year-old male patient underwent an urgent endovascular procedure of a contained ruptured abdominal aortic aneurysm using a Cook Zenith prosthesis. After 7 months the patient was readmitted with clinical signs of a prosthetic infection. CT scan was assessed as a possible prosthesis infection. An ¹⁸F-FDG PET/CT scan confirmed the diagnosis by showing an increased FDG uptake at the level of the endograft. Ultimately, Escherichia coli were cultured from the graft.