[18F]-Fluorodeoxyglucose PET/CT imaging as a marker of carotid plaque inflammation: Comparison to immunohistology and relationship to acuity of events.

BACKGROUND

[18F]-fluorodeoxyglucose (FDG) uptake imaged with positron emission tomography (PET) and computed tomography (CT) may serve as a biomarker of plaque inflammation. This study evaluated the relationship between carotid plaque FDG uptake and a) intraplaque expression of macrophage and macrophage-like cellular CD68 immunohistology; b) intraplaque inflammatory burden using leukocyte-sensitive CD45 immunohistology; c) symptomatic patient presentation; d) time from last cerebrovascular event.

METHODS

54 patients scheduled for carotid endarterectomy underwent FDG PET/CT imaging. Maximum 18FDG uptake (SUV) and tissue-to-blood ratio (TBR) was measured for carotid plaques. Quantitative immunohistological analysis of macrophage-like cell expression (CD68) and leukocyte content (CD45) was performed.

RESULTS

FDG uptake was related to CD68 macrophage expression (TBR: r = 0.51, p < 0.001), and total-plaque leukocyte CD45 expression (TBR: r = 0.632, p = 0.009, p < 0.001). FDG TBR uptake in carotid plaque associated with patient symptoms was greater than asymptomatic plaque (3.58 ± 1.01 vs. 3.13 ± 1.10, p = 0.008). FDG uptake differed between an acuity threshold of <90 days and >90 days (SUV:3.15 ± 0.87 vs. 2.52 ± 0.45, p = 0.015).

CONCLUSIONS

In this CAIN cohort, FDG uptake imaged with PET/CT serves a surrogate marker of intraplaque inflammatory macrophage, macrophage-like cell and leukocyte burden. 18FDG uptake is greater in plaque associated with patient symptoms and those with recent cerebrovascular events. Future studies are needed to relate FDG uptake and disease progression.