Identification of atherosclerotic lipid deposits by diffusion-weighted imaging.
OBJECTIVE
The content and distribution of lipids is an important aspect of plaque vulnerability, but lipids are present within a heterogeneous environment, impeding detection by magnetic resonance imaging. Our goal was to achieve accurate detection of mobile lipids by a single magnetic resonance imaging sequence.


RESULTS
Carotid endarectomy specimens (n=23) were imaged ex vivo at a high magnetic field (11.7 T) within 24 hours after surgery. Three contrast-weighted (T1W, T2W, and diffusion-weighted imaging [DWI]) image sequences were acquired and then coregistered with histological preparations for lipids (Oil red O and polarized light microscopy) and fibrous tissue (trichrome). Contrast-to-noise ratios were measured and compared for the 3 contrast weightings. Contrast-to-noise ratio measurement in regions identified as lipid versus fibrous tissue showed greater differences by DWI (4.5+/-0.63 versus 0.64+/-0.08; P<0.05) as compared with T2W (2.83+/-0.36 versus 1.36+/-0.37; P<0.05). We validated the presence and distribution of lipids (mainly cholesteryl esters) by both histology and image-guide spectroscopy. The basis for distinguishing mobile lipid and water inside the plaque was illustrated by diffusion-weighted spectroscopy.


CONCLUSIONS
Biophysical properties of plaque lipids can confer selective identification by DWI, as opposed to standard T1W and T2W imaging sequences. Successful translation of DWI in vivo could identify of features of vulnerable plaque.
Qiao
Ye
Y
Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118, USA.
Ronen
Itamar
I
Viereck
Jason
J
Ruberg
Frederick L
FL
Hamilton
James A
JA
D000368:Aged; D050197:Atherosclerosis / Q000175:diagnosis / Q000378:metabolism* / Q000473:pathology / Q000601:surgery; D016893:Carotid Stenosis / Q000378:metabolism* / Q000473:pathology / Q000601:surgery; D002788:Cholesterol Esters / Q000032:analysis; D038524:Diffusion Magnetic Resonance Imaging; D016894:Endarterectomy, Carotid; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008055:Lipids / Q000032:analysis*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008859:Microscopy, Polarization; D008875:Middle Aged; D015203:Reproducibility of Results; D013194:Staining and Labeling / Q000379:methods; D014867:Water / Q000032:analysis
D002788:Cholesterol Esters; D008055:Lipids; D014867:Water