Role of 18F-FDG positron emission tomography in carotid atherosclerotic plaque imaging: A systematic review

Abstract

Stroke and other thromboembolic events in the brain are often due to carotid artery atherosclerosis, and atherosclerotic plaques with inflammation are considered particularly vulnerable, with an increased risk of becoming symptomatic. Positron emission tomography (PET) with 2-deoxy-2-[Fluorine-18] fluoro-D-glucose (¹⁸F-FDG) provides valuable metabolic information regarding arteriosclerotic lesions and may be applied for the detection of vulnerable plaque. At present, however, patients are selected for carotid surgical intervention on the basis of the degree of stenosis alone, and not the vulnerability or inflammation of the lesion. During the past decade, research using PET with the glucose analog tracer ¹⁸F-fluor-deoxy-glucose, has been implemented for identifying increased tracer uptake in symptomatic carotid plaques, and tracer uptake has been shown to correlate with plaque inflammation and vulnerability. These findings imply that ¹⁸F-FDG PET might hold the promise for a new and better diagnostic test to identify patients eligible for carotid endarterectomy. The rationale for developing diagnostic tests based on molecular imaging with ¹⁸F-FDG PET, as well as methods for simple clinical PET approaches, are discussed. This is a systematic review, following Preferred Reporting Items for Systematic Reviews guidelines, which interrogated the PUBMED database from January 2001 to November 2019. The search combined the terms, "atherosclerosis," "inflammation," "FDG," and "plaque imaging." The search criteria included all types of studies, with a primary outcome of the degree of arterial vascular inflammation determined by ¹⁸F-FDG uptake. This review examines the role of ¹⁸F-FDG PET imaging in the characterization of atherosclerotic plaques.

Keywords: 18F-FDG; atherosclerosis; carotid artery; carotid endarterectomy; plaque imaging; vulnerable plaque.

Figure 1

Computed tomography angiography (a), fused positron emission tomography/computed tomography (b) and positron emission tomography alone (c) demonstrating a left carotid plaque in a symptomatic patient showing high ¹⁸F-FDG uptake

Figure 2

Contrast-enhanced computed tomography (left), fused positron emission tomography/computed tomography (middle) and positron emission tomography alone (right) in patients with symptomatic carotid artery stenosis. Right-sided carotid artery stenosis with vessel wall calcifications and mild 18F-FDG uptake (a). Note the normal physiological uptake in salivary glands. Left-sided carotid plaque with moderate ¹⁸F-FDG uptake (b). Note the dense physiological uptake in the right longus capitis muscle and parotid gland

Figure 3

Transaxial ¹⁸F-FDG positron emission tomography/computed tomography image (a) demonstrating focal avid ¹⁸F-FDG uptake in the carotid plaque (arrowhead). Corresponding axial computed tomography image (b) showing a low attenuating plaque in the left carotid artery (arrowhead)

Figure 4

Transaxial ¹⁸F-FDG Positron emission tomography alone image (a) and positron emission tomography/computed tomography image (b) demonstrating high uptake in the left internal carotid artery. Computed tomography angiography image (c) demonstrating severe stenosis of the left internal carotid artery with an atherosclerotic plaque