O 7-1 MR Plaque imaging of hypoechoic carotid plaques

Introduction : Hypoechoic plaque on carotid ultrasonography is usually considered to be vulnerable, but can include various histological components such as fibrous tissue, lipid, and hemorrhage. Hence, we investigated whether MR plaque imaging can distinguish components within the hypoechoic carotid plaque. Methods : We prospectively examined 27 patients (29 carotid arteries) with hypoechoic carotid plaques by a non-gated motion-corrected T1-weighted MR plaque imaging technique. Eight of 29 arteries underwent a carotid endarterectomy (CEA). Signal intensity of the carotid plaque was manually measured, and the contrast ratio (CR) relative to the adjacent muscle was calculated. We also compared imaging findings with those of histological specimens obtained by CEA. Results : On MR plaque imaging, CRs of 29 hypoechoic carotid plaques remarkably varied (0.69-2.70 ; 1.39±0.47). Among these,‘hypointense' plaque (CR : 1.5 ; 1.51-2.70 ; 1.89±0.34) were observed in 21%, 41%, and 38%, respectively, and well corresponded to fibrous tissue, lipid, and hemorrhage on the specimens, respectively. Conclusion : Non-gated T1-weighted MR plaque imaging enables us to estimate histological components within the hypoechoic carotid plaques.