Measurement of the Intimal Thickness of the Carotid Artery: Comparison Between 40 MHz Ultrasound and Histology in Rats

Common carotid artery intimal thickness (IT) has been shown to be as useful as a measurement of the whole layer of intima-media thickness (IMT) for evaluating the early phase of atherosclerosis. The aim of this study was to elucidate the relationship between high echogenic intimal thickening (HEIT), which was measured using a 40 MHz ultrasound biomicroscope (UBM), and the histologically determined IT in rat carotid arteries. HEIT was estimated in 10 Wistar-Kyoto rats (group I), 15 spontaneous hypertensive rats (SHR) fed a standard diet (group II) and 10 SHR fed a high-fat diet (group III). IT and IMT measurements were determined in Masson trichrome-stained tissues and were compared with the HEIT and IMT evaluated using the UBM. In group I, the HEIT and the IT were 33 ± 4 μm and 12 ± 1 μm, respectively. In group II, the HEIT and the IT were 68 ± 8 μm and 16 ± 2 μm, respectively. In group III, the HEIT and the IT were 65 ± 26 μm and 33 ± 14 μm, respectively. In SHR, the HEIT and the mean IMT measured with echography were significantly correlated with the IT and the IMT that were determined by histologic measurement (r = 0.60, p = 0.003 and r = 0.53, p = 0.01, respectively). Moreover, HEIT may be associated with the intimal pathology and atherosclerotic burden. The HEIT measurement is a noninvasive method that may be used to assess atherosclerosis in humans. (E-mail:[email protected]).