We examined the tissue characterization of carotid plaques using integrated backscatter (IB) and correlated it with the histological analysis in 15 patients who subsequently underwent carotid endarterectomy (CEA). All 15 patients, 11 male and 4 female, mean age 68 years, with carotid stenotic (70% or greater lumen reduction) atherosclerotic plaques verified by angiography and B-mode ultrasonography were included in this study. A 7.5 MHz probe was used to obtain IB value. The pathological examination (HE and Masson trichrome stains) was carried out at a similar level of the isonation. The IB value of normal carotid wall was －14.9±3.8 dB. The IB value of fatty tissue (－19.0±5.0 dB) was significantly lower than fibrotic (－14.0±6.2 dB) and calcific (＋2.1±6.3 dB) content (P<0.01). The intraplaque hemorrhage site exhibited very low backscatter value (－24.0±5.0 dB) which was even lower than the fatty tissue value. The integrated backscatter provides quantitative assessment of plaque structures. The IB value of the atherosclerotic plaque is useful in distinguishing lipidic, fibrotic, calcific, and hemorrhagic content.
