Inflammation in carotid atherosclerotic plaque: a dynamic contrast-enhanced MR imaging study.
OBJECTIVE
To prospectively evaluate if there is an association between plaque enhancement at magnetic resonance (MR) imaging and proinflammatory cardiovascular risk factors and plaque content.


METHODS
This study was performed with informed consent, HIPAA compliance, and institutional review board approval. Contrast agent dynamics within carotid plaques were measured in 30 patients (29 men, one woman; mean age, 67.7 years +/- 10.7 [standard deviation]) who were scheduled to undergo carotid endarterectomy. Measurements were based on kinetic modeling of images obtained at 15-second intervals during which a gadolinium-based contrast agent was injected. The time-varying signal intensities within the plaques were used to estimate the fractional plasma volume (vp) and transfer constant (Ktrans) of contrast material into the extracellular space. Pearson correlation coefficients were computed between blinded MR measurements and histologic measurements of plaque composition, including macrophages, neovasculature, necrotic core, calcification, loose matrix, and dense fibrous tissue. Correlation coefficients or mean differences were computed regarding clinical markers of cardiovascular risk.


RESULTS
Analyzable MR images and histologic results were obtained in 27 patients. Measurements of Ktrans correlated with macrophage (r = 0.75, P < .001), neovasculature (r = 0.71, P < .001), and loose matrix (r = 0.50, P = .01) content. Measurements of v(p) correlated with macrophage (r = 0.54, P = .004), neovasculature (r = 0.68, P < .001), and loose matrix (r = 0.42, P = .03) content. For clinical parameters, significant associations were correlated with Ktrans only, with decreased high-density lipoprotein levels (r = -0.66, P < .001) and elevated Ktrans measurements in smokers compared with nonsmokers (mean, 0.134 min(-1) vs 0.074 min(-1), respectively; P = .01).


CONCLUSIONS
The correlations between Ktrans and histologic markers of inflammation suggest that Ktrans is a quantitative and noninvasive marker of plaque inflammation, which is further supported by the correlation of Ktrans with proinflammatory cardiovascular risk factors, decreased high-density lipoprotein levels, and smoking.
Kerwin
William S
WS
Department of Radiology, Division of Cardiology, and Department of Surgery, University of Washington, 815 Mercer St, Seattle, WA 98109, USA. bkerwin@u.washington.edu
O'Brien
Kevin D
KD
Ferguson
Marina S
MS
Polissar
Nayak
N
Hatsukami
Thomas S
TS
Yuan
Chun
C
D000368:Aged; D000369:Aged, 80 and over; D050197:Atherosclerosis / Q000473:pathology* / Q000601:surgery; D016893:Carotid Stenosis / Q000473:pathology* / Q000601:surgery; D003287:Contrast Media / Q000008:administration & dosage / Q000493:pharmacokinetics*; D016894:Endarterectomy, Carotid; D005260:Female; D019786:Gadolinium DTPA / Q000008:administration & dosage / Q000493:pharmacokinetics*; D006801:Humans; D007249:Inflammation / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012044:Regression Analysis
D003287:Contrast Media; C064925:gadodiamide; D019786:Gadolinium DTPA