Elsevier

Molecular Imaging & Biology

Volume 5, Issue 1, January–February 2003, Pages 23-25
Molecular Imaging & Biology

Brief Article
PET/CT Using 2-Deoxy-2-[18F]Fluoro-D-Glucose for the Evaluation of Suspected Infected Vascular Graft

https://doi.org/10.1016/S1536-1632(03)00035-0Get rights and content

Abstract

An infected vascular graft was identified using a combined positron emission tomography (PET) and computerized tomography (CT) system. The fusion of 2-deoxy-2-[18F]fluoro-D-glucose (FDG) PET and CT images, acquired in a single session, allowed for the precise localization of the abnormal FDG uptake to the vascular graft and led to the correct diagnosis of prosthetic infection. This hybrid modality, which provides precise registration of metabolic and structural imaging data, may enhance the potential use of FDG in the diagnosis and man-agement of infected vascular grafts.

Introduction

Graft infection is an uncommon but potentially severe complication following prosthetic vascular reconstruction. The clinical presentation is often subtle and may occur long after surgery. Accurate and timely diagnosis of this condition is important for further management, since graft infection may be associated with limb loss and high mortality.1., 2. Positron emission tomography (PET) using 2-deoxy-2-[18F]fluoro-D-glucose (FDG) has evolved from a research imaging modality to a clinical tool for the assessment of malignancies. FDG, a nonspecific tracer of increased intracellular glucose metabolism, has been found to accumulate not only in malignant cells but also in sites of infection and inflammation.3 The value of FDG in the diagnosis of infected vascular graft has not been previously investigated. In addition, PET, although highly sensitive, often lacks the ability to define the precise anatomic location of a site of abnormal FDG accumulation. The new technology of PET tomography (CT), combining a dedicated PET system and high resolution CT, mounted on the same assembly and sharing a common table, has been recently introduced. This hybrid modality provides precise registration of metabolic and structural imaging data, obtained in the same session, on a single device and has the potential of improving diagnosis and correct localization of prosthetic graft infection.4

A 72-year-old male presented to the vascular surgery outpatient clinic with a recurrent nonhealing wound (ulcus cruris) in his left ankle. Prior to his admission he was unsuccessfully treated with hyperbaric oxygen and a skin graft. The patient had a history of heavy smoking, mild chronic renal failure (creatinine 1.9 mg/dl), and hypertension. Physical examination revealed large varicosities with post phlebitic syndrome in both legs, more advanced in the left leg. The capillary refill time was increased, for more than two seconds, no pulses could be felt below the femoral pulse and the ankle-brachial index was low, 0.5.

Angiography of the lower left limb demonstrated diffuse arteriosclerosis. The superficial femoral artery and the popliteal artery were occluded as well as the anterior and peroneal arteries. The only patent artery in the calf and foot was the posterior tibial artery. The patient underwent a limb salvage procedure during which a left femoro-posterior tibial bypass was fashioned. Large chronic varicosities in the patient's veins made these vessels unsuitable for use in a bypass procedure and an 8-mm ringed Gortex (PTFE) graft was therefore used. The patient was discharged after an uneventful recovery.

A month later the patient presented with an infected, pus-secreting surgical wound in the region of the graft, treated by drainage and antibiotics. Two months later, he was readmitted with fever (38.6 C°) and a leucocytosis of 18×103/mm3. The surgical wound was hot and red, without secretion or fluctuation. The patient was referred for FDG-PET/CT imaging for a clinically suspected infection of the vascular graft.

A PET/CT study of the pelvis and thighs down to the knees was performed one hour after the injection of 10 mCi (370 MBq) of FDG using the combined PET/CT scanner (Discovery LS, GEMS, Milwaukee, WI, USA). Neither oral nor intravenous contrast media were used for CT acquisition.

The positional information of the table and patient is shared for both the CT and PET acquisitions to ensure proper registration of the two images. CT is used for low-noise attenuation correction of PET emission data, and for fusion of attenuation-corrected PET images with the corresponding CT slices. PET images are reconstructed using Ordered Subset Expectation Maximization (OSEM), with measured CT attenuation correction. As acquisition is completed, the reconstructed and attenuation-corrected PET study, as well as the CT and fused images, are available for review, displayed in axial, coronal and sagittal planes, and in three-dimensional cine mode.

Section snippets

Results

PET images demonstrated abnormal FDG uptake along the medial aspect of the left thigh, from the level of the groin to the knee. The uptake was more prominent in the proximal and in the distal portion of the left thigh, suggesting either an infected graft or the infected surgical wound (Figure 1). On the PET/CT fused images the distal focus is precisely localized to the vascular graft (Figure 2). Additional foci of abnormal FDG uptake are localized in areas corresponding to the vascular graft

Discussion

Graft infection is a severe complication of vascular reconstructive surgery with high morbidity and mortality.1 Its accurate diagnosis is challenging and relies mainly on a combination of clinical symptoms and imaging findings. CT is considered the procedure of choice in diagnosis of graft infection. A persistent opacity and the presence of perigraft soft tissue fluid and gas have been described as features associated with graft infection. Sensitivity of CT can reach up to 100%, but decreases

References (13)

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