Inflammation within carotid atherosclerotic plaque: assessment with late-phase contrast-enhanced US.
OBJECTIVE
To determine if the number of nontargeted microbubbles retained in human carotid plaque is sufficient to be detected with ultrasonography (US).


METHODS
The study protocol was approved by the local research ethics committee. Informed consent was obtained. A total of 37 subjects with carotid atherosclerosis (mean age, 69.9 years; age range, 49-86 years), of whom 27 (73%) were men (mean age, 69.7 years; age range, 58-86 years) and 10 (27%) were women (mean age, 70.3 years; age range, 49-86 years), were studied between December 2008 and May 2009 with late-phase (LP) contrast material-enhanced US by using flash imaging with a nonlinear mode at an intermediate mechanical index of 0.34 6 minutes after bolus contrast agent injection. Plaques were defined as symptomatic if symptoms consistent with stroke, transient ischemic attack, or amaurosis fugax had occurred in the neurovascular territory of the plaque studied within 12 months prior to entry into the study. Plaques were defined as asymptomatic if no such events had ever occurred within the neurovascular territory. Raw linear data were used to quantify echogenicity of the plaque, which was normalized to lumen echogenicity. Gray-scale median score was also calculated.


RESULTS
Of the 37 subjects, 16 (43%) had symptomatic plaques and 21 (57%) had asymptomatic plaques. All examinations yielded evaluable LP contrast-enhanced US data. Normalized LP plaque echogenicity was greater in the symptomatic group (0.39; 95% confidence interval: -0.11, 0.89) than in the asymptomatic group (0.69; 95% confidence interval: -1.04, -0.34) (P = .0005). There was a moderate (rho = -0.44, P = .016) inverse correlation between normalized LP plaque echogenicity and gray-scale median score.


CONCLUSIONS
By quantifying microbubble retention within the carotid plaque, LP contrast-enhanced US depicts clear differences between groups of subjects with plaque ipsilateral to symptoms and asymptomatic plaques. This technique has promise as a tissue-specific marker of inflammation and a potential role in the risk stratification of atherosclerotic carotid stenosis.
Owen
David R
DR
Department of Experimental Medicine and Toxicology, Imperial College London, Hammersmith Hospital, Du Cane Road, London W12 0NN, England. d.owen@imperial.ac.uk
Shalhoub
Joseph
J
Miller
Sam
S
Gauthier
Thomas
T
Doryforou
Ortansia
O
Davies
Alun H
AH
Leen
Edward L S
EL
D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D002340:Carotid Artery Diseases / Q000000981:diagnostic imaging* / Q000473:pathology; D003287:Contrast Media / Q000008:administration & dosage; D005260:Female; D006801:Humans; D007249:Inflammation / Q000000981:diagnostic imaging / Q000473:pathology; D007275:Injections, Intravenous; D008297:Male; D045423:Microbubbles; D008875:Middle Aged; D010743:Phospholipids / Q000008:administration & dosage; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D013459:Sulfur Hexafluoride / Q000008:administration & dosage; D014463:Ultrasonography
D003287:Contrast Media; D010743:Phospholipids; C420843:contrast agent BR1; D013459:Sulfur Hexafluoride