Noninvasive vascular elastography: toward a complementary characterization tool of atherosclerosis in carotid arteries.

Only a minority of patients with carotid arterial disease have warning symptoms, because the majority of strokes are caused by previously asymptomatic lesions. Because morbidity and mortality after acute stroke are high, patients should be diagnosed and treated before symptoms develop. The hypothesis of this study is that vascular elasticity maps (or elastograms) of carotids are of predictive value for plaque characterization. The strain tensor from either cross-sectional or longitudinal ultrasound radiofrequency data were assessed by a new implementation of the Lagrangian speckle model estimator (LSME), which considers local echogenicity variations. A 26-year-old healthy male (HS1), a 40-year-old (HS2) normal female subject and two 75-year-old asymptomatic patients with severe carotid stenoses were scanned. Reproducible elastograms were obtained as a function of time over five to seven cardiac cycles. Stress-strain modulus elastograms were computed for normal subjects. Stiffening of healthy carotid walls was estimated to be 148 +/- 7 kPa and 163 +/- 30 kPa at peak-systole for HS1 and HS2, respectively. For patients with heterogeneous plaques, strain and shear elastograms revealed interesting information about plaque size, tissue composition and mechanical interaction between structures. In conclusion, the LSME provides a promising approach for strain and shear estimates to characterize vulnerable plaque.