Abstract 14702: Evaluation of Inflammation in Carotid Disease by New Imaging Modalities: Implications From 18-FDG PET/CT and Microwave Radiometry

Abstract

Background and Purpose: Nowadays, 18F fludeoxyglycose Positron Emmision Tomography/computed tomography (18F-FDG PET/CT) is the leading modality for tracing inflammation within atherosclerotic plaques in vivo, but patients’ exposure to radiation, costs and availability limit its widespread use. We hypothesize that microwave radiometry (MWR), a safe noninvasive method allowing in vivo estimation of atherosclerotic process by measuring temperatures of tissues could be an accurate alternative tool for assessing lesional inflammation. Therefore, the aim of the present study was to investigate the relationship between temperature differences and FDG uptake assessed by MWR and 18F-FDG PET/CT respectively, in patients with significant carotid disease. Methods: Consecutive patients, scheduled for carotid endarterectomy due to significant carotid artery (CA) stenosis, underwent 18F-FDG PET/CT and MWR. PET/CT images were acquired 90 min after FDG injection. FDG uptake was measured as maximal standardized uptake value (SUVmax) in consecutive axial slices starting at the bifurcation and extending 2 cm superiorly and 2 cm inferiorly. During MWR evaluation, ΔΤ (maximal temperature across the carotid artery minus minimum) was calculated over the respective carotid segments. Results: In total, 44 CAs from 22 patients (18 male) were studied. There was a significant positive correlation between ΔT and SUVmax values in the operated arteries and also between the same parameters in all 44 vessels (R=0.44, p=0.05 and R=0.44, p=0.005, respectively). Operated and non-operated CAs demonstrated similar ΔT and SUVmax values (0.57±0.19 vs 0.59±0.17 °C, p=0.67 and 2.18±0.44 vs 2.28±0.41, p=0.48 respectively). In addition, there was no correlation between the degree of angiographic stenosis and ΔT values (R=0.07, p=0.65) or between lesional SUV measurements and the percentage of luminal stenosis (R=0.10, p=0.55). Conclusions: There is a significant correlation between FDG uptake and thermal heterogeneity, indicating that MWR is a promising marker of plaque inflammation. Moreover, there is discrepancy between stenosis severity and inflammation intensity assessed by FDG uptake and MWR, highlighting the diversity of processes involved in CA atherosclerosis.