title: Identification of cholesteryl esters in human carotid atherosclerosis by ex vivo image-guided proton MRS.
abstract: Vulnerable atherosclerotic plaques may be identified by their large lipid component, particularly liquid cholesteryl ester (CE), covered by a fibrous cap. We hypothesized that image-guided 1H proton magnetic resonance spectroscopy (MRS) would identify mobile CE in discrete, preselected regions of atherosclerotic plaque. Human carotid endarterectomy specimens (n = 10) were imaged ex vivo by magnetic resonance imaging (MRI) at high field (11.7 T) utilizing standard T1- and T2-weighted spin echo protocols. MRS spectra were acquired from 1 mm3 voxels, localized to plaque regions that we judged by MRI to be lipid rich or lipid poor. The spectra revealed methyl and methylene resonances of fatty acyl chains with relative intensities and linewidths characteristic of pure CE, by comparison with lipid standards. Regions judged to be lipid rich by MRI showed much more intense CE resonances than did lipid-poor regions. The integrated intensities of lipid peaks were 5.5 +/- 2.0% (lipid-rich regions) versus 0.9 +/- 0.6% (lipid-poor regions) of the unsuppressed water peak (P < 0.0001). Lipid distribution by histology, MRS, and MRI showed strong correlation. Image-guided proton MRS accurately identified CE in selected regions of atherosclerotic plaque as small as 1 mm3 in an ex vivo setting. This procedure may permit the noninvasive detection and quantification of CE in atherosclerotic plaque in vivo.
authors.affiliation: Whitaker Cardiovascular Institute, Evans Department of Medicine and Section of Cardiology, Boston University School of Medicine, Boston, MA, USA.
authors.forename: Frederick L
authors.initials: FL
authors.lastname: Ruberg
authors.forename: Jason
authors.initials: J
authors.lastname: Viereck
authors.forename: Alkystis
authors.initials: A
authors.lastname: Phinikaridou
authors.forename: Ye
authors.initials: Y
authors.lastname: Qiao
authors.forename: Joseph
authors.initials: J
authors.lastname: Loscalzo
authors.forename: James A
authors.initials: JA
authors.lastname: Hamilton
mesh_terms: D002340:Carotid Artery Diseases / Q000378:metabolism* / Q000473:pathology; D002788:Cholesterol Esters / Q000032:analysis* / Q000737:chemistry / Q000592:standards; D006801:Humans; D066298:In Vitro Techniques; D008051:Lipid Bilayers / Q000737:chemistry; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D010743:Phospholipids / Q000737:chemistry; D011522:Protons; D012015:Reference Standards; D014280:Triglycerides / Q000737:chemistry
chemical_list: D002788:Cholesterol Esters; D008051:Lipid Bilayers; D010743:Phospholipids; D011522:Protons; D014280:Triglycerides