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PET/CT Detects Early Atherosclerosis in Large Arteries

January 12, 2008
Written by: , Filed in: Cardiac Imaging
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A noninvasive technique to detect vulnerable atherosclerotic plaque is needed. Ultrasound, multislice CT, and MRI have been employed for this purpose, but have inherent limitations.
FDG-PET/CT holds the most potential for this purpose. FDG uptake in large arteries detected by PET was first noted in patients with vasculitis. FDG uptake was linked to atherosclerosis in the abdominal aorta, iliac, and proximal femoral arteries in 156 patients who had undergone PET for other purposes. Hypercholesterolemia correlated consistently with FDG uptake. Recent work demonstrates FDG uptake in carotid atherosclerosis related to serum matrix metalloproteinase-1, which has been associated with advanced atherosclerosis and plaque rupture. FDG uptake reflects active plaque inflammation, while calcification detected by CT indicates an advanced stage. Congruent FDG uptake and calcification were observed in only 2% to 14% of the sites in different studies. FDG-PET imaging can potentially measure the inflammatory component in atherosclerotic plaque. Rudd et al show that deoxyglucose accumulated in plaque macrophages in carotid endarterectomy specimens in vitro. FDG uptake was higher in symptomatic lesions than in the contralateral asymptomatic lesions. Recent work demonstrated significant correlation between FDG-PET in carotid plaques and macrophage staining from the corresponding histological sections of specimens after endarterectomy. FDG-PET may assess the degree of inflammation and identify lesions that are responsible for embolic events. A prospective clinical study suggests that FDG-PET may monitor drug-induced changes in plaque inflammation.
Forty-three subjects were randomly assigned to either strict dietary management or administration of simvastatin plus dietary management. After 3 months, FDG-PET showed a significant decrease of FDG uptake in the atherosclerotic plaques in the simvastatin group, whereas no change occurred in the dietary management alone group. Statins promote plaque stability by decreasing plaque macrophage content and activity.
FDG-PET can identify the decrease of plaque inflammation much earlier than the anatomic changes detected by MRI, which are reportedly detected after 12 months. The standardized uptake value (SUV) can provide quantitative information about the severity of the inflammatory process in the arterial wall. Bural et al developed a quantitative method to measure the extent of atherosclerosis in the aorta by combining SUV with CT volumetric data of the aortic wall.

Reviewer’s Comments
From the collection of comments and data in this paper, it seems that FDG-PET/CT is the most sensitive method currently available to detect atherosclerosis in the large arteries. The next step is to prove that early detection and accurate evaluation are worth the considerable cost of entering PET/CT into this large clinical arena.
Take-Home Pearl
There is evidence that FDG-PET/CT can detect early inflammatory plaque formation in large vessels that can lead to embolic events.
Author: Richard Goldfarb, MD
Reference:
Chen W, Bural GG, et al. FDG-PET Imaging Tackles Large Arteries With Atherosclerosis.
Diagn Imaging; 2007; October 1: S1-3

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