Original Article
Uptake of F-18 FDG and ultrasound analysis of carotid plaque

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Abstract

Objectives

To elucidate the relation between the echolucent plaque on carotid ultrasound and acute inflammation on F-18 FDG carotid PET/CT.

Methods

Thirty nine patients (M:F ratio = 23:16, mean age = 63 ± 11 years) that underwent coronary angiography and carotid ultrasound were divided into three groups—echolucent plaque (n = 22), calcified (n = 10), and no plaque(n = 7). All the patients underwent F-18 FDG carotid PET/CT. The mean standardized uptake values (SUV), namely target to background ratio (TBR) on 180 minutes delayed F-18 FDG carotid PET/CT images were compared with levels of serum inflammatory markers and lipid profiles, and in terms of the presence of carotid plaque on carotid US.

Results

180 minutes TBR of carotid arterial wall at echolucent plaque, calcified plaque, and no plaque were 1.40 ± 0.05, 1.23 ± 0.03, 1.17 ± 0.03 in both carotid artery. TBR of carotid arterial walls for echolucent plaque were significantly larger than TBR for calcified, and no plaque respectively at the both side of carotid artery (P < .05). Serum HDL levels were found to be inversely correlated with F-18 FDG uptake at both carotid arteries (r = −0.43, P = .005) on 180 minutes delayed phase images. Also serum hs-CRP levels were found to be correlated with F-18 FDG TBR values of right carotid arteries (r = 0.41, P = .04).

Conclusions

Our results show that F-18 FDG carotid PET/CT can depict metabolically active atherosclerotic plaques, and suggest that F-18 FDG carotid PET/CT can be used as a noninvasive imaging modality for functional evaluation of atherosclerosis.

Introduction

Rupture of atherosclerotic plaque is a major cause of cardiovascular events. Plaque containing numerous inflammatory cells (particularly macrophages) thought to be associated with a high risk of rupture. Moreover, conventional angiography cannot identify high risk plaque, because plaque rupture is more related to plaque content than size. Therefore, there is an urgent need for a molecular imaging method capable to identifying plaque at risk of rupture. Present endeavors include the targeting of lipid, thrombus, apoptosis, monocytes, and inflammation. In the imaging targets considered, the detection of inflammation is likely to be of value because of the well-documented association between inflammatory processes and plaque rupture.1, 2, 3, 4, 5, 6 Preliminary data demonstrate that 18F-fluorodeoxyglucose (F-18 FDG) positron emission tomography (PET) can identify inflamed atherosclerotic plaques in animal models of atherosclerosis.7, 8, 9 Furthermore, Rudd et al10,11 demonstrated increased carotid F-18 FDG uptake in patients with evidence of a recent ischemic cerebrovascular event. Recent studies have shown that plaque echolucency and IMT on carotid ultrasound are independent determinants for cerebrovascular events.12 More importantly, in low-to-moderate grade lesions, plaque echolucency affords incremental predictive value to IMT in predicting the odds of a clinical event.13 However, no direct evidence has been presented that these echolucent plaques on carotid US show increased uptake in F-18 FDG carotid PET/CT images in asymptomatic patients. The purpose of this study is to elucidate the relation between the echolucent plaque on carotid ultrasound and F-18 FDG carotid PET/CT. In addition, we evaluated the associations between increased F-18 FDG uptake and serologic inflammatory markers.

Section snippets

Method

Thirty nine consecutive patients (male:female = 23:16, mean age 63 ± 11 years) with no history of cerebral artery disease or myocardial infarction within recent 6 months who were referred for coronary angiography were recruited. F-18 FDG Carotid PET/CT was performed within 3 days of B-mode carotid ultrasound. Serologic markers were evaluated at the day of Carotid PET/CT scanning. Detailed clinical histories regarding the presence of cardiovascular risk factors, such as diabetes, obesity,

Clinical Characteristics

Patient clinical characteristics are shown in Table 1. The serum glucose level of seven NIDDM patients were relatively well controlled with oral hypoglycemic agent. No patient had a known cerebral artery disease or neurologic symptom.

F-18 FDG Uptakes and Type of Carotid Plaque

180 minutes delayed TBR values of carotid arterial wall at echolucent plaque, calcified plaque, and no plaque were 1.40 ± 0.05, 1.23 ± 0.03, 1.17 ± 0.03 in both carotid artery (Figure 3). TBR of carotid arterial walls for echolucent plaque were significantly larger

Discussion

F-18 FDG accumulates in carotid atherosclerotic plaques and shows significantly higher uptakes in culprit lesion than in nonculprit lesions for stroke.10 Because most deoxyglucose accumulates in macrophage-rich plaque areas, these findings suggest that inflammation is present to a greater degree in culprit lesion than in nonculprit lesion for stroke. Moreover, despite the limited spatial resolution of PET, this study shows that integrated PET/CT device can be used to F-18 FDG uptake to

Conclusion

F-18 FDG carotid PET/CT was found to be capable of depicting metabolically active atherosclerotic plaque. Our findings add to the body of evidence supporting the use of F-18 FDG carotid PET/CT for non-invasive functional evaluation of atherosclerotic carotid plaque

References (17)

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